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  • 1965-1969  (15.544)
  • 1920-1924  (4.191)
  • Polymer and Materials Science  (8.218)
  • Inorganic Chemistry  (7.229)
  • Organic Chemistry  (4.288)
Materialart
Erscheinungszeitraum
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  • 101
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 7 (1969), S. 2073-2089 
    ISSN: 0449-2978
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Dilatometric melting experiments were performed on an extended-chain crystalline polyethylene with a broad molecular weight distribution and on four samples crystallized from fractionated polyethylenes. The melting curves were compared with computer calculations based on the assumption of eutectic separation. For the fraction of lowest molecular weight, agreement between experiment and calculation was achieved. The melting behavior of all other samples indicated that only for molecular weights up to 10,000-12,000 did eutectic separation occur. The higher molecular weight portion of each sample crystallized in the form of mixed crystals. Of the experimental maximum melting-point lowering of these mixed crystals, 0.1-0.9°C is due to the lower molecular weight diluents. Another 2-3°C lowering in melting point is due to the fact that the phase diagram of polyethylene mixed crystals has a minimum.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
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  • 102
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 7 (1969), S. 1585-1594 
    ISSN: 0449-2978
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: A comparison is made between the experimentally obtained molecular weight distributions of nitric acid-oxidized polyethylene with a wide range of initial morphologies and the predictions of a random attack model. Deviations from the theoretical expectations are explained.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
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  • 103
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 7 (1969), S. 2144-2144 
    ISSN: 0449-2978
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Materialart: Digitale Medien
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  • 104
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 7 (1969), S. 1755-1760 
    ISSN: 0449-2978
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Rates of crystallization of polyethylene fractions have been studied at high undercoolings by differential calorimetry to demonstrate the utility of this technique for fast crystallization analysis. It has been shown that there is continuity in the crystallization kinetics from low to high undercoolings. On the other hand, the influence of molecular weight on the crystallization rates, as the undercooling increases, is very moderate, as would be expected.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
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  • 105
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 7 (1969), S. 1745-1754 
    ISSN: 0449-2978
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The yield-stress behavior of two glassy polymers is studied through the glass transition region over a wide range of strain rates. For temperatures below the glass transition temperature, the yield stress behavior could be described as a non-Newtonian flow in agreement with Eyring's theory, if one excepts a narrow range relating to the slowest strain rates. For temperatures above Tg, the yield-stress behavior is still nonlinear but fits the relations based on the concept of free volume.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
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  • 106
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 7 (1969), S. 1937-1954 
    ISSN: 0449-2978
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The distribution of molecular weights in realistic free-radical polymerizations with branching was analyzed theoretically. Series solutions were obtained for the fraction of molecules with r repeating units and the number of branch points contained in molecules with r repeating units. Branching by transfer processes was found to increase the proportion of both high and low molecular weight components in the system. The apportioning of branch points among r-mer molecules was shown to be somewhat narrower than a Poisson distribution. The major difference between the calculated distributions and previous model distributions for branched systems was the absence of discontinuities in the moments at all levels of branching.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
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  • 107
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 7 (1969), S. 1983-1986 
    ISSN: 0449-2978
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
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  • 108
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 7 (1969), S. 2005-2018 
    ISSN: 0449-2978
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The problem of the structural theory of macromolecular networks is formulated and discussed in general terms. The conditions required for a system to become a homogeneous macromolecular network are defined and discussed. Networks are divided according to the nature of their junctions into three classes: energetic (with chemical or quasi-chemical crosslinks), topological (with entangled chains), and contact (with frictional interactions). The main features of these three classes are discussed. A distribution density function ψ describing the configurations of macromolecules in network systems is introduced. The phase space of variables is 4(N + 1)-dimensional and includes the coordinates of (N + 1) vectors hi joining the adjacent network junctions and (N + 1) contour lengths li of the network chains. The system of simultaneous equations required for the determination of the function ψ includes the equation of continuity, kinematic equations for the deformation velocity of the individual junctions, the force balance equation needed for the determination of sliding rates li, kinetic equations for the processes of junction breakage and reformation, and the equilibrium distribution of network junctions defining the initial conditions for the distribution function ψ.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
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  • 109
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 7 (1969), S. 2061-2072 
    ISSN: 0449-2978
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Extended-chain crystals of high molecular weight polymethylene, a polyethylene with a broad molecular weight distribution, and three fractions of polyethylene were grown from the melt under elevated pressure. Comparison of the crystal size distribution in the molecular chain direction (measured on fracture surfaces by electron microscopy) with the molecular weight distribution (measured by gel-permeation chromatography) gave the following results. Up to molecular weight 10,000 all samples showed eutectic separation into fully extended chain crystals of narrow molecular weight distribution. Above molecular weight 10,000 mixed crystals were formed. Under the chosen crystallization conditions larger chain extension was achieved with higher molecular weights. However, an increase in molecular weight by a factor of 1000 led only to a tenfold increase in chain extension. These facts are discussed in the light of a proposed mechanism of crystal growth.
    Zusätzliches Material: 12 Ill.
    Materialart: Digitale Medien
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  • 110
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 7 (1969), S. 2115-2138 
    ISSN: 0449-2978
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The Kuhn-Grün theory for the birefringence and dichroism of rubbery polymers is extended to the case of copolymers consisting of two or more statistical segments of differing lengths. It is shown that the previous equations are applicable provided that the anisotropy of polarizabilities and absorptions are replaced with suitable averages in which the segment anisotropies are weighted by the squares of their segment lengths. This indicates that the stress-optical coefficient will not generally vary linearly with composition. The orientation measured from the dichroism of bands arising from different segments will be different.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
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  • 111
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 7 (1969), S. 47-55 
    ISSN: 0449-2978
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: A method of determining the distribution of branching in polydisperse polymer samples is proposed. This method uses data from concurrent gel permeation chromatography and sedimentation-velocity experiments. Tedious fractionation, which must precede other methods of determining long-chain branching, is eliminated. An example of use of the method on the data of a sample of styrene-divinylbenzene copolymer is given.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
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  • 112
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 7 (1969), S. 105-111 
    ISSN: 0449-2978
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Heterogeneous nucleation and crystallization of FEP Teflon and nylon 6 melts against high energy surfaces (i.e., gold) produce an interfacial region, in these polymers, of high mechanical strength. Dissolution of the metal substrate rather than removal by mechanical means results in a polymer surface which is amenable to conventional structural adhesive bonding. Nucleation and crystallization of the polymer melts in contact with phases of low surface energy (e.g., vapor) result in the generation of weak boundary layers.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
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  • 113
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 7 (1969), S. 171-182 
    ISSN: 0449-2978
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: To clarify the deformation mechanism in polyblends of polypropylene with ethylene-propylene rubber having different compositions, simultaneous measurements of the infrared dichroism with stress and strain under a constant rate of strain of 1.64%/min have been carried out. The orientation function of the crystallographic c axis of polypropylene in the blends has been obtained as a function of strain ranging from 0 to 20% and of polypropylene content ranging from 0.3 to 1.0. These results have been compared with the temperature dependences of the dynamic Young's modulus and of the loss modulus, as well as of stress-strain curves for the same blends. The modulus data analyzed by Kerner's equation reveal the occurrence of phase inversion at polypropylene contents higher than about 0.5, and this is supported by the infrared dichroism data. The strong effect of quenching on crystalline structure and mechanical properties of pure polypropylene has also been elucidated.
    Zusätzliches Material: 12 Ill.
    Materialart: Digitale Medien
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  • 114
    ISSN: 0449-2978
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Results from characterization of melt-polymerized nylon 66 by various solution property measurements are reported and employed in analysis of typical molecular weight and compositional distributions for these systems. Critical attention is paid to application of standard procedures including light scattering, viscosity, membrane osmometry and other colligative property measurements in arriving at satisfactory specification of polymer molecular weight averages. Particular consideration is given to polymers extending appreciably beyond the lower and higher limits in molecular weight normally encountered. The conclusions drawn are: (1) in the range of number-average molecular weights less than about 25 000, nylon 66 as ordinarily prepared by melt condensation consists principally of linear species approximating the “most probable” distribution; (2) small amounts of cyclic oligomers are present in all samples: (3) increase in the extent of the melt polycondensation to progressively higher stages is accompanied by secondary reactions and the formation of branched components terminating ultimately in crosslinked, insoluble gels. Intrinsic viscosity-molecular weight relationships in seven solvents, applicable to nylon polymers meeting the requirements of (1) above, are derived.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
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  • 115
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 7 (1969), S. 57-76 
    ISSN: 0449-2978
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: For an infinitely repeated regular polymer chain structure the only vibrations which are optically active are those in which the phase of the motion is the same in each unit (the factor-group modes). Frequencies for which the phase difference is nonzero are optically inactive but can become activated by the presence of defects in the chain. Such defects would normally be chemical impurities or conformational irregularities in the chain. A simple theory is developed which shows that for a dilute system of defects the major characteristics determining possible activation of the nonfactor-group modes are: (1) the strength of the coupling between the defect vibration and the vibrations of the neighboring chain, and (2) whether or not the natural frequency of the defect vibration lies inside a lattice band of the regular chain. An analysis of the low- and high-frequency regions of the spectrum of low-density polyethylene, based on the above considerations, indicates that several features of the spectrum can be associated with defect-induced absorption. A similar explanation can account for certain intensity changes in the C—Cl stretching region of syndiotactic poly(vinyl chloroide) when this polymer is submitted to mechanical treatment.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
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  • 116
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 7 (1969), S. 253-254 
    ISSN: 0449-2978
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Materialart: Digitale Medien
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  • 117
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 7 (1969), S. 309-324 
    ISSN: 0449-2978
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The Huggins and Kraemer equations generally used to determine intrinsic viscosity frequently do not yield identical results, and their constants often do not add up to 1/2 as is mathematically required. To overcome these difficulties an equation has been deduced which through linear plots gives unambiguous intrinsic viscosities, constants which meet the 1/2 condition, as well as two other flow constants. Extensive tests of the equation with precise data on solutions of poly(methyl methacrylates) and polystyrenes in benzene and toluene confirm the validity of the new equation in every respect. It is further shown that the four constants involved are interrelated, and that it is possible to express the values of three of these in terms of the fourth.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
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  • 118
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 7 (1969), S. 431-431 
    ISSN: 0449-2978
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Materialart: Digitale Medien
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  • 119
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 7 (1969), S. 483-495 
    ISSN: 0449-2978
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The peak separation in gel-permeation chromatography (GPC) is attributed to the contributions of the steric exclusion and the lateral diffusion processes. The advantage of using the distribution coefficient KGPC of the solute molecule in interpreting the GPC separation mechanism is assessed. The physical significance of KGPC and its relation to measurable GPC parameters are examined in detail. A simple mixing experiment for determining the exclusion effect is described. The results of this experiment, as well as those of the flow rate study, show that the exclusion effect plays the primary role in GPC peak separation. For a column packed with Bio-Rad porous glass of 200 Å designation, the diffusion effect does not contribute significantly to peak separation. However, for the case of a Waters Associates column packed with polystyrene gel of 104 Å designation, both the exclusion and the diffusion effects are shown to be important. A diffusion theory which includes the concept of a restricted diffusion coefficient is proposed to interpret the diffusion effect observed in the polystyrene gel column. The results of the theoretical calculation are found to agree with the observed flow rate dependence of the calibration curve.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
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  • 120
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 7 (1969), S. 537-549 
    ISSN: 0449-2978
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Thermogravimetric analyses (TGA) of catalyst-free polydimethylsiloxanes (PDMS) have been carried out in controlled atmospheres and a kinetic analysis of the results has enabled the various decomposition processes to be separated and identified. The calculated activation energy for thermal depolymerization is 42 ± 3 kcal/mole, while thermo-oxidation has an apparent activation energy of 30 ± 2 kcal/mole. Quantitative analyses of the major degradation products and molecular weight distribution studies of the residues from degradation studies under isothermal conditions have shown that in vacuo, PDMS fractions depolymerize to cyclic dimethylsiloxanes and low molecular weight linear residues by a randomly initiated mechanism which, it is postulated, involves the formation of an intramolecular, cyclic, four-centered transition state followed by siloxane bond rearrangement. This mechanism is a basic property of linear PDMS fractions and is independent of molecular weight. Molecular weight distribution (MWD) changes observed from further isothermal investigations on hydroxy endblocked PDMS fractions, have shown the presence of a chain-lengthening process in vacuo below the depolymerization temperature. This process, with an apparent activation energy of 8.6 ± 1 kcal/mole, is attributed to the intermolecular condensation of terminal hydroxyl groups.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
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  • 121
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 7 (1969), S. 575-586 
    ISSN: 0449-2978
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The intrinsic viscosities of fractions of poly(ethylene oxide) in the molecular weight range 1.5 × 103 to 106 have been measured at 25°C in benzene, carbon tetrachloride, and acetone; at 35°C in 0.45M aqueous potassium sulfate; and at 50°C in methyl isobutyl ketone and diethylene glycol diethyl ether. The latter three are practically theta solvents. The value of (r02/M)1/2 for poly(ethylene oxide) is calculated to be 0.84 Å from the molecular weights of the high molecular weight fractions, and their intrinsic viscosities in the theta solvents and acetone. Erroneous values result if the usual methods of determination are applied to the data obtained for the low molecular weight (〈104) fractions or to the intrinsic viscosities in the very good solvents, benzene and carbon tetrachloride.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
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  • 122
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 7 (1969), S. 609-633 
    ISSN: 0449-2978
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Molecular weight determinations by light scattering and osmometry and intrinsic viscosity measurements were made in various solvents on fractions of styrene-methyl acrylate copolymers with different compositions and on acrylate homopolymers prepared by free-radical reaction. Relations between intrinsic viscosity [η] and molecular weight M thus established are compared with those reported by other authors. 2-Methylcyclohexanol was found to be a theta solvent for the copolymers and both parent homopolymers, and isoamyl acetate was a theta solvent for poly(methyl acrylate). From theta point viscosity data obtained with these solvents, unperturbed chain dimensions were estimated. The results are compared with the unperturbed dimensions estimated from the [η]-M relations obtained in good solvents. On the basis of the experimental data it was found that the unperturbed dimension depends linearly on the copolymer composition, in contrast to the case of styrene-methyl methacrylate copolymers. Composition dependences of the theta temperature and of the parameter describing the long-range interactions between nonadjacent segments in polymer chains were investigated. The result implies that long-range interactions between monomeric units never disappear even when those between the same monomeric units vanish. The Huggins constant for copolymer is discussed in terms of the excluded volume variable.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
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  • 123
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 7 (1969), S. 1151-1163 
    ISSN: 0449-2978
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The strength-limiting process in the fracture of semicrystalline fibers and highly oriented films is the rupture of tie molecules connecting the folded chain lamellae in the machine direction. This view is supported by the data on stress and temperature dependence of lifetime of fibers under load and on radical formation during the fracture experiment. The observed tensile strength, however, is about 10 times smaller and the number of fractured chains between 100 and 1000 times larger than expected on the basis of the known number of tie molecules in the fracture plane. This discrepancy is a consequence of the inhomogeneity of the micromorphology of fiber structure, which causes a much larger stress concentration on the most unfavorably located tie molecules than the average value one would expect in the case of perfectly uniform stress distribution on identical tie molecules. The fluctuation of amorphous layer thickness, of number and length of tie molecules, produces such a high stress concentration on some tie molecules throughout the sample that they rupture long before the average stress concentration is sufficient for chain fracture. By accumulation of damage caused by gradual chain rupture the weakening of the sample locally proceeds so far that at the maximum damage concentration, microcracks start to form, and the fiber breaks.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
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  • 124
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 7 (1969), S. 1259-1274 
    ISSN: 0449-2978
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Model fibers of polyethylene and nylon 6 were strained in the direction of the fiber axis and the internal deformation of the samples was studied by large-angle and small-angle x-ray diffraction. The compression of samples along the fiber axis was successfully carried out, and the results obtained by x-ray methods yielded more interesting information on the structure of the fibers than was obtained in extension. A model for the structure of the fiber was constructed on the basis of the results on compressed fibers. In this model, crystals are distributed in cylindrical symmetry around the fiber axis keeping a crystal axis tangential to circles in the section normal to the fiber axis. The characteristic crystal axis is the b axis in polyethylene and the a axis in nylon 6. The chain axis of the crystals varies in orientation with respect to the fiber axis. In compression of fibers with such a structure, the crystals rotate around the characteristic axis indicated above. In the case of nylon 6 fiber, only this simple rotation seems to occur, while additional changes occur in polyethylene fibers. However, the simple rotation predominates even in polyethylene fibers. This fiber structure is correlated with the structure of thin films of the materials. This similarity proves the existence of a common mechanism for the origin of the structure of fibers and films.
    Zusätzliches Material: 15 Ill.
    Materialart: Digitale Medien
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  • 125
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 7 (1969), S. 1315-1328 
    ISSN: 0449-2978
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The circumstances of the formation of kink bands have been investigated with a newly designed shearing device and light and electron microscopes. Kink bands having sharp edges and reflection symmetry about the edges were formed and studied in the two crystalline polymers, high-density polyethylene and isotactic polypropylene, but could not be formed in the two glassy polymers, poly(4,4′-dioxydiphenyl-2,2-propane carbonate) and poly(2,6-dimethylphenylene oxide). The characteristics of the oriented polymer that promote kink bands seem to be easy slip along the orientation axis, and resistance of the oriented fibrils to length changes. Kink bands were found to initiate at sites of shear stress concentration, where the fibrils are first deformed into an S-shaped curve, that then tightens and finally collapses into kinks.
    Zusätzliches Material: 11 Ill.
    Materialart: Digitale Medien
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  • 126
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 7 (1969), S. 750-750 
    ISSN: 0449-2978
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Materialart: Digitale Medien
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  • 127
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 7 (1969), S. 775-782 
    ISSN: 0449-2978
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: A statistical model for the stereospecific polymerization of vinly monomers on Ziegler-Natta catalytic systems is presented. The basic assumptions of the model are: (a) the catalytic centers are asymmetric, so that at a given catalytic center the monomer CH2=CHR is inserted into the chain with two different rates according to the two different configurations of the opening carbon atom having the R group; (b) the insertion of a monomeric unit in the growing chain is affected also by interactions with the previous monomeric unit. Isotactic, syndiotactic, atatic, or stereoblock polymers are obtained according to the relative values of the two energy parameters expressing these two effects.
    Zusätzliches Material: 1 Ill.
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  • 128
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 7 (1969), S. 821-827 
    ISSN: 0449-2978
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: A specimen of linear polyethylene was subjected to isothermal secondary crystallization at a series of temperatures below the primary isothermal crystallization temperature, the melting and primary crystallization stages being held constant throughout the investigation. Dilatometric measurements exhibit an S-character at low values of undercooling Tp - Ts, where Tp and Ts are, respectively, the primary and secondary crystallization temperatures, whereas at larger undercooling, an initial very rapid crystallization is followed by a very slow stage. When corrected for thermal contraction of the polymer, the net degree of secondary transformation is seen to peak at a temperature about 5°C below Tp. The S-character of the isotherms and the peaked temperature variation of degree of transformation lead to the conclusion that a large portion of the secondary crystallization consists of the nucleation and growth of the new crystallites. Johnson-Mehl-Avrami analysis leads to a model of heterogeneous nucleation within the remaining amorphous zones, followed by one-dimensional, diffusion-controlled growth.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
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  • 129
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 7 (1969), S. 855-866 
    ISSN: 0449-2978
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Heats of solution (ΔHexp) in solvents of increasing thermodynamic power have been measured for four polymers: polystyrene (PS), poly(vinyl acetate) (PVAc), polyisobutylene (PIB) and polydimethylsiloxane (PDMS). After subtraction from ΔHexp of an interaction term (calculated by the Hildebrand treatment based on solubility parameters) and the excess volume term, the quantity remaining is interpreted as the conformational energy contribution (ΔUconf) to the heat of solution. ΔUconf appears to correlate well with some basic conformational properties of the chain, such as the sign of the temperature coefficient of unperturbed dimensions derived from solution properties, and shows a monotonic behavior with α, the expansion coefficient of the polymer coil in the final solution. Numerical values of ΔUconf, at least for those cases in which polymer solubility parameters are known with some certainty, are much larger than those evaluated from rubber elasticity experiments (through the experimentally accessible value of the energy component of the force of retraction im simple elongation).
    Zusätzliches Material: 5 Ill.
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  • 130
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 7 (1969), S. 909-927 
    ISSN: 0449-2978
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Non-Newtonian shear viscosities were measured over six decades of strain rate k for 13 solutions of both the ionic and nonionic forms of polyacrylamide. By using the Weissenberg rheogoniometer with both the cone-and-plate and the parallel-plate attachments, the normal stress functions σ1 (k2) and σ2(k2) were obtained for four of the solutions. From the measurements of the shear viscosity and the normal stresses at low rates of strain, characteristic times τ and τN, respectively, were determined for each solution. The quantity τ was then used to nondimensionalize the strain rate τk, and when plotted versus the reduced shear viscosity, found successfully to correlate the experimental data for all the polyelectrolyte solutions over the entire range of τk and the data for the concentrated solutions of the nonionic polymer over a smaller range of τk. However, in order to correlate the normal stress data for the polyelectrolyte solutions, a second reduced strain rate (τNk) was used. Thus, two different times were required to correlate all the observed data. The shear viscosity data for the dilute solutions of the nonionic polymer were well represented by the two-parameter, non-Newtonian intrinsic viscosity function that has been computed by Fixman.
    Zusätzliches Material: 19 Ill.
    Materialart: Digitale Medien
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  • 131
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 7 (1969), S. 1539-1558 
    ISSN: 0449-2978
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The scattering patterns are calculated from anisotropic rods having an arbitrary angle of the polarizability axis with respect to the rod axis. The effect of a distribution of orientation of the rods is explored. This leads to a change in scattering patterns produced by orienting the rods upon stretching the sample. The scattering patterns are affected by the relationship between the refractive indexes of the rods and that of the surroundings. The influence of the optic axis orientation angle changing upon orienting the rods is explored. Theoretical patterns are compared with experimental ones obtained upon stretching polytetrafluoroethylene (PTFE) films.
    Zusätzliches Material: 13 Ill.
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  • 132
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 7 (1969), S. 1619-1621 
    ISSN: 0449-2978
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
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  • 133
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 7 (1969), S. 1279-1279 
    ISSN: 0449-2978
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
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  • 134
    ISSN: 0449-2978
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Electron microscopic textures of A-B type block copolymers of styrene and isoprene cast from several solvents were investigated by means of the osmium tetroxide fixation technique. The two-phase structure, i.e., the semimicro heterogeneous structure due to the microphase separation of block segments, was observed to change systematically with the fraction of block segments and the kind of solvent. Three types of fundamental domain structure were found. With the assumption that domain structure originates from micellar structure at a critical concentration in relatively dilute solution during solvent casting, the formation of the three types of domain structure and the sizes of their elements were treated in terms of the equilibria governing the formation of micelles at the critical concentration. This analysis takes into account such thermodynamic and molecular parameters as the incompatibility between the A and B segments, the solvation of the segments, the casting temperature, the total chain length of the block copolymer, and the weight fraction composition of the block copolymer. It was concluded that the block segments are preferentially oriented along the direction perpendicular to the interface between the two phases. This particular orientation-aggregation of the block segments must make the bulk properties of the block copolymer much different from those of merely mechanical mixtures of the corresponding homopolymers, even if the same semimicro heterogeneous structures are formed in the mechanical mixtures.
    Zusätzliches Material: 11 Ill.
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  • 135
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 7 (1969), S. 1379-1383 
    ISSN: 0449-2978
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The surface tensions of solutions of polyisobutylene fluids in n-heptane and tetralin have been measured at room temperature. The polyisobutylene samples studied range in molecular weight from 400 to 2800. The results conform closely to the predictions of equations previously developed from a simplified lattice theory calculation.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
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  • 136
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 7 (1969), S. 1393-1403 
    ISSN: 0449-2978
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Attempts to prepare undamaged microtomed sections of crazes without reinforcement have failed. Several methods of reinforcing crazes in glassy polymers with impregnants prior to microtomy have been tried. Generalized characteristics of successful impregnant systems are suggested on the basis of this experience. The most successful system has involved the infusion of liquid sulfur into crazes in poly(2,6-dimethyl-1,4-phenylene oxide). After quenching, the solid sulfur reinforces the crazes successfully during microtomy but subsequently sublimes away under vacuum. The resultant, largely undamaged craze structure is seen by transmission electron microscopy to resemble an open-cell foam, the holes and polymer elements of which uniformly average ∼200 Å in diameter. A moderate degree of orientation in the original tensile stress direction is observed. Implications drawn from craze structure for the existence of order in the glassy state are discussed.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
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  • 137
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 7 (1969), S. 1483-1487 
    ISSN: 0449-2978
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Expansion of a small spherical hole in a highly elastic solid is treated theoretically. Both elastic and surface energy terms are considered; the corresponding surface forces are assumed to be additive. The surface energy of the elastomer is assumed to be similar to that of simple liquids. Pressures or triaxial tensions required to inflate pre-existing holes to an indefinitely large size are calculated. Small holes require extremely large pressures, of the order of 1000 atm for holes of 10 Å radius. These results suggest a means of determining the distribution of hole sizes in elastomers and account in principle for experimental observations of cavitation processes. Detachment of the elastomer from a small rigid inclusion is treated in a similar way. The general absence of dilation or cavitation on stretching carbon black-filled elastomers is thus accounted for solely in terms of the small size of these filler particles.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
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  • 138
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 7 (1969), S. 1525-1537 
    ISSN: 0449-2978
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The mechanical and rheo-optical properties of a styrene-butadiene-styrene block copolymer of a given chemical composition are dependent upon the morphology of the polymer as affected by the solvent system from which a polymer film is cast. Films cast from methyl ethyl ketone and from toluene are compared. Properties found to differ are the stress-strain curve, the birefringence-strain curve, stress relaxation birefringence relaxation, and the dynamic mechanical spectra.
    Zusätzliches Material: 11 Ill.
    Materialart: Digitale Medien
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  • 139
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 7 (1969), S. 2139-2140 
    ISSN: 0449-2978
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 140
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 7 (1969), S. 1623-1626 
    ISSN: 0449-2978
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 141
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 7 (1969), S. 1721-1733 
    ISSN: 0449-2978
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Dielectric measurements of carefully purified specimens of polystyrene and poly(2,3,4 or 3,4-chlorostyrene) have been obtained at audio frequencies ranging from 0.1 to 20 kHz and at temperatures between 4 and 300°K. Each of the samples exhibits a dielectric loss maximum in the range 15-50°K. The temperature of the maximum loss decreases with the addition of a substituent which lowers the symmetry of the pendant phenyl group. The results are explained by a model which invokes a coupling mechanism between two distinct modes of side group motions. This same model also explains some results of previously reported measurements of mechanical losses in similar polymers.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
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  • 142
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 7 (1969), S. 1681-1694 
    ISSN: 0449-2978
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Creep compliance data, J(t), at 35°C for poly(β-hydroxyethyl monomethacrylate), crosslinked by ethylene glycol dimethacrylate in a range of concentration C from 0.0855 to 2.053 × 10-4 mole/cm3 and swollen to various degrees in diluents, were examined for time-concentration superposition. From the dependence of time scale shift factors on v2, the volume fraction of polymer, free volume parameters were calculated for two samples with C = 0.0855 × 10-4 and 0.136 × 10-4 mole/cm3, swollen in the range of v2 from 0.134 to 0.591. Special attention was given to the magnitude of the shift factor on the log J(t) axis and its dependence on concentration, which was found to depend substantially on the crosslinking and the swelling degrees of the samples. This shift was approximately log v2 for lightly crosslinked samples, swollen to a small degree, measured in the neighborhood of the main transition. For higher degrees of crosslinking and/or swelling, the shift was much less and for the most highly crosslinked networks swollen to equilibrium it was even negative. The correction appears to be very sensitive to the strain of the effective chains and to the location on the time scale with respect to the transition and rubberlike zones of viscoelasic behavior. It was found that the parameters of the WLF equation calculated in our previous study from the time-temperature superposition of the creep curves in the rubber-glass transition are valid also for the rubberlike region.
    Zusätzliches Material: 8 Ill.
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  • 143
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 7 (1969), S. 1775-1783 
    ISSN: 0449-2978
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: A systematic study of factors affecting the GPC separation showed that peak spreading with increasing flow rate was much less than predicted from the Van Deemter equation. Viscous fingering decreased and peak symmetry improved at increased flow rates. As a result, fast GPC analysis was shown to be readily attainable through optimization of operating parameters.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
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  • 144
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 7 (1969), S. 1835-1861 
    ISSN: 0449-2978
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Dielectric relaxation processes observed in solid polar polymers seem to be generally classified into three kinds. Amorphous polymers with flexible polar side groups usually show two kinds of relaxation process. The high-temperature process is attributed to the large scale conformational rearrangements of the main chains, while the low-temperature one results from the motion of side groups. We shall call the former αa relaxation and the latter β relaxation, where the subscript refers to the amorphous phase. Even in amorphous polymers without flexible side groups, two processes are observed. The molecular mechanism of high temperature one is the same as the αa relaxation. The low-temperature one is due to the “local relaxation mode” of the main chains. We shall call it also β relaxation because of the similarity of the observed characteristics. Semicrystalline polymers show two relaxation processes classified as αa and β, although their behavior is modified by crystallization. When the crystallinity is greatly increased, a third relaxation process with associated with crystalline phase appears. We shall call it αc relaxation, where the subscript means the crystalline phase. The effects of chemical structure, stereoregularity, pressure, and crystallization on the dielectric behavior can be explained consistently based on the above molecular mechanisms.
    Zusätzliches Material: 30 Ill.
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  • 145
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 7 (1969), S. 1907-1918 
    ISSN: 0449-2978
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: A new apparatus for investigating dynamic strain birefringence in polymer films at frequencies up to 10 Hz and at various degrees of internal sample orientation is described. Samples are elongated at constant low rates while simultaneously being strained sinusoidally. Fast changes in sample retardance are recorded while slow changes are automatically compensated with a servo-controlled Soleil-Babinet compensator. The signal-to-noise ratio of the system is greatly enhanced by incorporating a highly monochromatic laser light source, a synchronous amplifier, and a light beam modulator based on a rotating polarizer. Data obtained from this apparatus can be used to elucidate polymer relaxation mechanisms at various frequencies over a wide range of static strains.
    Zusätzliches Material: 4 Ill.
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  • 146
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 7 (1969), S. 1965-1982 
    ISSN: 0449-2978
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Raman spectra are described for the three crystalline modifications of polybutene-1. The Raman frequencies are compared with infrared results and give good agreement. A normal-coordinate analysis for A-mode vibrations is presented for five possible helical conformations. The behavior of several calculated helix-sensitive bands is characterized. These results are applied to the experimental Raman frequencies and lead to the prediction of a 103 helix for the orthorhombic form III modification.
    Zusätzliches Material: 8 Ill.
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  • 147
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 7 (1969), S. 87-104 
    ISSN: 0449-2978
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: This paper reports an electron microscopy study of the morphology of crystals of poly(vinylidene chloride) prepared under a variety of conditions and of the carbons resulting from the pyrolysis of the polymer. The structure of the polymer carbons prepared under conditions such that the polymer does not pass through a plastic phase is closely related to the morphology of the original polymer. The shapes of the crystals and of the crystal pseudomorphs are indexed in terms of the unit cell proposed by Narita and Okuda. Morphological studies of this kind are important in discussing the graphitizability of polymer carbons, their mechanical properties and pore structure, and the kinetics of the dehydrochlorination reaction.
    Zusätzliches Material: 13 Ill.
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  • 148
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 7 (1969), S. 183-200 
    ISSN: 0449-2978
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Equipment and methods have been developed which allow photomicrographic determination of the stress-strain properties of the individual craze. Serial cyclic tensile tests on polycarbonate crazes are described. Under stress the typical dry polycarbonate craze thickens solely by straining; no adjacent polymer of normal density is converted to craze material. The craze exhibits a yield stress followed by a recoverable flow to roughly 40-50% strain at 6000-8000 psi. On return to zero stress the craze exhibits creep recovery at a decelerating rate. The yield stress and loss factor of each cycle decrease with increasing initial strain and cycles initiating at 50% strain or more show completely Hookean behavior. Creep recovery results in recovery of yield stress and loss factor also. Craze tensile behavior is suggested to be essentially an extension of the craze formation process. Decrease in elastic modulus and yield stress with increasing strain are rationalized in terms of strain-produced decrease in density and resultant increase in stress concentration factor on the microscopic polymer elements of the craze. Polymer surface tension and the large internal specific surface area of the craze are suggested to be important factors in the large creep recovery rates of the craze.
    Zusätzliches Material: 10 Ill.
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  • 149
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 7 (1969), S. 241-248 
    ISSN: 0449-2978
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: A method of determining distributions of the degree of polymerization by means of probability theory is derived. This method, based on Kolmogorov's forward differential equation, is illustrated by application to two familiar kinetic schemes and is used to derive the distribution of degree of polymerization for free-radical polymerization with diffusion-controlled termination.
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  • 150
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 7 (1969), S. 249-252 
    ISSN: 0449-2978
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: NO ABSTRACT.
    Materialart: Digitale Medien
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  • 151
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 7 (1969), S. 279-284 
    ISSN: 0449-2978
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The effect of birefringence on light scattering is considered, using classical theory. It is shown that in conjunction with polarized light scattering, the use of birefringence can aid in the reduction of experimental errors; also how new checks on theory can be made. The treatment is applied to scattering from simple gaseous molecules and thin polymeric films.
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  • 152
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 7 (1969), S. 271-278 
    ISSN: 0449-2978
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The effect of birefringence of a polymer film upon its photographic light-scattering pattern is considered for the case of a single, anisotropic, two-dimensional spherulite imbedded in a birefringent matrix. It is shown that for the case of a polarizer and analyzer crossed at +45° and -45° to the analyzer, the scattering pattern is modified in a manner agreeing with experimental observation.
    Zusätzliches Material: 5 Ill.
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  • 153
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 7 (1969), S. 285-295 
    ISSN: 0449-2978
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Osmotic-pressure, viscosity, and light-scattering measurements have been carried out on dilute solutions of poly-N-vinylcarbazole fractions (4 〈 10-4M 〈 230) in toluene, dioxane, and benzene. The theta temperature for poly-N-vinylcarbazole in toluene solutions has been found to be 37 ± 1°C. The intrinsic viscosity of poly-N-vinylcarbazole in toluene at 37°C is represented by [η]θ = 76.2 × 10-3M̄n0.50. Values of the characteristic ratios (〈L2〉0/M)1/2 and σ = (〈L2〉0/〈L2〉0f)1/2 have been obtained as 633 × 10-11 and 2.85, respectively. It appears that the large σ value is due to the steric repulsion between large side groups.
    Zusätzliches Material: 7 Ill.
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  • 154
    ISSN: 0449-2978
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Mechanical relaxation data as a function of temperature (ca. 1 Hz) have been obtained for several samples of isotactic polypropylene crystallized from the melt, which exhibit both α and β forms as well as varying degrees of lamella orientation. The samples ranged in morphology from an unoriented sample showing only the α form to one highly oriented having approximately 90 per cent the β form. Results for the logarithmic decrement Δ and loss modulus G″ are that the low temperature (ca. -75°C) and glass temperature (ca. 0°C) relaxations show little or no sensitivity to orientation in the α form, but that the intensity of the two processes is different in the α form than in the β form for samples of nearly equal overall per cent crystallinity. In both Δ and G″, the low-temperature peak decreased and the glass temperature peak increased in intensity as the fraction of β form crystallinity present increased. Data for the high-temperature relaxation (ca. 80°C) indicate a dependence upon orientation and/or crystal form in addition to a dependence upon per cent crystallinity.
    Zusätzliches Material: 6 Ill.
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  • 155
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 7 (1969), S. 433-462 
    ISSN: 0449-2978
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The intrachain and interchain vibrations below 900 cm-1 of polydimethylsiloxane (PDMS) have been studied by slow neutron inelastic scattering. A composite motion observed at +25°C for the methyl groups corresponds to nearly free rotation about the threefold axis of symmetry together with a large-amplitude rotation of the entire methyl group. At -123°C, rotation about the threefold axis evolves to a torsional oscillation. The large-amplitude rotation evolves to the skeletal vibrations of a helical conformation. Vestiges of the cooperative skeletal vibrations of the conformation at -123°C persist into the 25°C spectrum. The results indicate the presence of interrupted helical conformations at 25°C, which result from thermal disordering of the low temperature helices. The effects of crosslinking, low molecular-weight oils, and silica filler on the freedom of the methyl group motions and on skeletal vibrations have been determined. The effects of different crosslinking agents and different relative amounts of filler and oil on both the macroscopic physical properties and the observed molecular motions of PDMS can also be interpreted in terms of an interrupted helix.
    Zusätzliches Material: 16 Ill.
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  • 156
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 7 (1969), S. 475-481 
    ISSN: 0449-2978
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Experiments in which an oscillatory shear flow is superimposed on a steady state shear flow were performed on polyethylene melts by the use of a cone and plate type rheogoniometer. The phase difference between oscillatory shear stress and shear strain increases in all cases and for all frequencies with the increase of the superimposed shear rate. Between ω0, the frequency at which the phase difference is π/2 and the steady shear rate \documentclass{article}\pagestyle{empty}\begin{document}$ \dot \gamma $\end{document}, as found by Booij for polymer solution, the relation ω0 = 1/2 \documentclass{article}\pagestyle{empty}\begin{document}$ \dot \gamma$\end{document}. holds also for polyethylene melts. The significance of this relation is discussed briefly from the viewpoint that the entanglement density decreases with the increase of the imposed shear rate.
    Zusätzliches Material: 9 Ill.
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  • 157
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 7 (1969), S. 497-513 
    ISSN: 0449-2978
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Triplet → singlet energy transfer in nylon 66 film (donor) dyed with proflavine (acceptor) is demonstrated by a decrease of the nylon phosphoresence lifetime and an increase in the proflavine delayed fluorescence/nylon phosphoresence ratio with increasing proflavine concentration. Although the observed donor phosphorescence decay is apparently exponential, the transfer is probably via a long-range dipole-dipole (Förster) interaction, rather than by triplet exciton migration. Arguments are advanced to support this view. Proflavine delayed fluorescence produced by a direct excitation process is also observed. The decay time for this process is roughly an order of magnitude less than that for the sensitized process. All emission intensities are shown to vary linearly with exciting light intensity. Finally, temperature dependence of proflavine delayed fluorescence under different excitation conditions is shown. The efficiency of direct excitation process increases markedly near -50°C as the temperature is increased; the sensitized delayed fluorescence intensity follows that of the nylon phosphorescence with increasing temperature, as expected.
    Zusätzliches Material: 7 Ill.
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  • 158
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 7 (1969), S. 587-592 
    ISSN: 0449-2978
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
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  • 159
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 7 (1969), S. 601-608 
    ISSN: 0449-2978
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The glass transition temperatures Tg of several fluorine-containing polymers were determined by use of the differential scanning calorimeter. Values between -3 and 230°C were obtained. In polymers of α-olefins, Tg increases with the fluorine content of the backbone and the length of the n-perfluoroalkyl branch. In styrene polymers Tg also is higher if the backbone contains fluorine but nearly the same Tg's are found for polymers with phenyl and pentafluorophenyl groups. Saturated polymers of perfluoro-α,ω-dienes have lower Tg's than polyperfluoro-α-olefins. The Tg's of chloroperfluoropolymers are higher than those of perfluoropolymers. Polyperfluoropentadiene-1,3 has the lowest Tg of the polymers examined. Polyperfluoropentadiene-1,3 forms by 1,4-addition.
    Zusätzliches Material: 1 Ill.
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  • 160
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 7 (1969), S. 667-674 
    ISSN: 0449-2978
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Drawn poly(ethylene terephthalate), PET, yarns have been heated for 1 min in silicone oil. The resulting samples were studied by x-ray diffraction and mechanical properties were measured. The results suggest that drawn PET consists of highly extended molecules essentially parallel to one another, with few folds present. On heating, chain folding occurs. This model is very similar to that proposed by Dismore and Statton for drawn nylon 66 yarns.
    Zusätzliches Material: 2 Ill.
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  • 161
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 7 (1969), S. 153-161 
    ISSN: 0449-2978
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The morphology of polyethylenes formed upon polymerization by γ-radiation below the melting point in various reaction media was investigated by using electron microscopy and scanning electron microscopy. When the polymerization was carried out in bulk at 30°C and in methanol, the polymer was fibrillar, and a small-angle x-ray scattering curve of the polymer did not indicate the existence of a long period. This suggests that the chains in the crystals have an extended conformation. When the polymerization was carried out in the presence of xylene at 30°C, platelet crystals having a folded structure were obtained. It was thus shown that the morphology of the growing polymer crystals is very much affected by the solubility of the polymer in the reaction medium. The effect of stirring during polymerization on the crystalline morphology was also studied.
    Zusätzliches Material: 5 Ill.
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  • 162
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 7 (1969), S. 209-217 
    ISSN: 0449-2978
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The intrinsic viscosity of a polymer in a solvent mixture is related to the excess free energy of the solvents. Intrinsic viscosities at different temperatures are obtained for poly-2-vinylpyridine-chloroform-ethyl alcohol, poly(methyl methacrylate)-chloroform-ethyl alcohol, polystyrene-cyclohexane-benzene, polystyrene-dioxane-chloroform, and polystyrene-cyclohexane-ethanol. Qualitative, but not quantitative, agreement is found between theory and experiment.
    Zusätzliches Material: 9 Ill.
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  • 163
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 7 (1969), S. 201-208 
    ISSN: 0449-2978
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Polymer crystals are characterized by strong anisotropy of binding forces among units, i.e., the intrachain force constant f is much larger than the interchain force constant g. The anisotropic lattice is reduced to an isotropic one, in which each lattice point represents N* units (segment) along the chain axis of the anisotropic lattice [N = 2(f/g)1/2]. Vibrational modes of the reduced lattice correspond to interchain modes of the original lattice, i.e., modes whose frequencies are governed by interchain potential. Anharmonicity of crystalline force field is assumed to be related predominantly with interchain force alone. Thermodynamic and transport equations for a simple lattice are applied to the reduced, isotropic lattice, and numerical results are obtained for high-density polyethylene. The Grüneisen constant γ was obtained from the pressure dependence of sound velocity. The heat capacity of the reduced lattice, Cinter (interchain specific heat), was calculated from Grüneisen's equation, α = γβCinter (where α = thermal expansion coefficient, β = compressibility), and the mass of a segment m* was estimated from Dulong-Petit's equation, Cinter = 3ρk/m* (where ρ = density, k = Boltzmann constant). The value of m* is consistent with N* from force constants, m* = N*m (where m = mass of a unit in the original lattice). m*θ3 (where θ denotes the Debye temperature of the reduced lattice) is calculated from low temperature specific heat. The value of m* calculated from m*θ3 and θ from other sources agrees with that from the estimate by Dulong-Petit's equation. The high-temperature thermal conductivity K was calculated through Leibfried-Schloemann's equation by employing γ and m*θ3 as estimated as described above; satisfactory agreement was obtained with experiment. Poly(methyl methacrylate) and polystyrene were also studied by similar methods.
    Zusätzliches Material: 3 Ill.
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  • 164
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 7 (1969), S. 1021-1031 
    ISSN: 0449-2978
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The discrepancy between the values of the anisotropy of methylene groups determined from crystal refractive indices, stress-optical data, and gas and liquid light-scattering depolarization is explained on the basis of the effect of the internal field on the polarizability of the isolated molecule. The internal field may arise from intermolecular or intramolecular interactions which depend upon molecular conformation and state of aggregation. A simple continuum calculation based upon an extension of the calculation of the Lorenz-Lorentz field is shown capable of accounting for the discrepancy.
    Zusätzliches Material: 5 Ill.
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  • 165
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 7 (1969), S. 1059-1073 
    ISSN: 0449-2978
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Nylon 66 films exhibiting form I melting behavior show the γ mechanical relaxation at -140°C. Samples which have form II melting behavior do not show this relaxation. The γ relaxation disappears when material having form I behavior is converted to material having form II behavior by annealing or by cold drawing. The form I and form II types of melting behavior are also found in poly(ethylene terephthalate); the interconversions and thermal behavior of the forms are analogous to the nylon 66 case. In poly(ethylene terephthalate), the β relaxation at -40 to -60°C is present only when form I melting behavior is found. Conversion to form II melting behavior by annealing or drawing (80°C) again causes the relaxation to disappear. No β relaxation was found in amorphous polymer. The γ dispersion in nylon 66 and the β dispersion in poly(ethylene terephthalate) can therefore be associated with the crystalline structure responsible for form I melting behavior. Form I melting behavior has been associated with foldedchain crystals based on previous work. It is therefore postulated that the γ dispersion in nylon 66 and the β dispersion in poly(ethylene terephthalate) are associated with motions in the chain folds. This assignment is not inconsistent with the change in the γ dispersion of nylon 66 with the number of backbone CH2 units, since these will affect the fold structure.
    Zusätzliches Material: 10 Ill.
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  • 166
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 7 (1969), S. 747-747 
    ISSN: 0449-2978
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Materialart: Digitale Medien
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  • 167
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 7 (1969), S. 1303-1314 
    ISSN: 0449-2978
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Column chromatographic fractionation of polystyrene was carried out with the methyl-ethyl ketone-methanol system, and effects of various experimental conditions on the fractionation efficiency were studied. For samples with molecular weights below about 6 × 105, neither the temperature gradient (0.7°C/cm), nor the flow rate of solvent (30-270 ml/hr) seriously influences the fractionation efficiency. The effect of temperature gradient becomes apparent only in the high molecular weight region and only if the gradient of the solvent composition is too steep. High flow rates (ca. 125 ml/hr) clearly affect the fractionation efficiency for a high molecular weight sample (Mw = 5.46 × 105). Precipitation chromatography for the fractionation system was calculated from the phase equilibrium data according to the mass transport equation proposed by Schulz et al. The theoretical analysis gives support to the observed dependence of the temperature effect on molecular weight. Comparison of the observed and theoretical relations between elution volume and molecular weight of the fraction, on the other hand, indicates that the process of fractionation is simply elution of polymer off the support without reprecipitation. Certain conditions of polymer deposition on the support are required for optimal results.
    Zusätzliches Material: 6 Ill.
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  • 168
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 7 (1969), S. 1367-1378 
    ISSN: 0449-2978
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Thin films of polyethylene prepared from blends of fractionated polymer and a linear hydrocarbon (n-C32H66) have been used to study the role of intercrystalline links in the deformation of semicrystalline polymer under uniaxial stress. These links have been found to be strong and virtually inextensible elements of the structure. It is shown that they are firmly attached to the chain-folded lamellar crystals they bridge (both within the same spherulite and across boundaries between adjacent spherulites) and that, by concentrating applied stress, they commonly induce these lamellae to begin yielding in regions close to their points of attachment. Where there are many closely spaced links the stress is distributed fairly evenly, and drawing is relatively smooth and uniform. With more sparsely distributed links, however, stresses tend to be concentrated at widely separated points; deformation then tends to be severe and highly localized, often resulting in failure of the material upon drawing. There are indications that stress is also transmitted between chain-folded lamellae in ways other than by intercrystalline links. One such way is by means of chain ends and molecular loops that emerge from the surfaces of these crystals and are embedded in interlamellar material. Experiments in which the deformed films were subsequently heated confirm earlier conclusions that extended chains in drawn polymer may undergo refolding during annealing.
    Zusätzliches Material: 11 Ill.
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  • 169
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 7 (1969), S. 1435-1438 
    ISSN: 0449-2978
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
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  • 170
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 7 (1969), S. 1461-1472 
    ISSN: 0449-2978
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Thermal analysis has been carried out on drawn nylon 6 filaments annealed at various temperatures between 150 and 210°C and then methoxymethylated to various degrees. It is shown that the melting point inherent to the morphology of drawn nylon 6 can be obtained from samples in which the reorganization of defect crystallites in the course of thermal analysis is prevented by a proper degree of methoxymethylation of amorphous regions. The melting point thus obtained is in linear relation with the reciprocal crystallite size in the direction of fiber axis which has been obtained from small-angle x-ray data and crystallinity. The extrapolation and the slope of this linear relation give the equilibrium melting point of nylon 6 as 245°C and an end-surface free energy of 42 erg/cm2. The results seem to provide strong support for the presence of chain-fold surfaces in the drawn and annealed polymers.
    Zusätzliches Material: 4 Ill.
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  • 171
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 7 (1969), S. 1489-1494 
    ISSN: 0449-2978
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The Raman scattering of nonplanar (form 2) poly(vinylidene fluoride) (PVF2) is described. Unique Raman bands not observed in the infrared spectra are found at 2973, 1437, 1327, 1198, and 1059 cm-1. Band assignments are discussed by comparing infrared and Raman spectra of form 2 PVF2.
    Zusätzliches Material: 1 Ill.
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  • 172
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 7 (1969), S. 963-981 
    ISSN: 0449-2978
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The structural and steric isomerism of propylene polymers has been estimated on the basis of solution properties as well as infrared and high-resolution nuclear magnetic resonance spectra. Three general types of polypropylenes were prepared: polymers prepared with the cationic catalytic system AlCl3-C2H5Cl, stereoblock polymers obtained by successive extraction from a commercial product and isotactic polymers of low molecular weight obtained by thermal degradation of a highly isotactic polymer followed by hydrogenation with Adam's catalyst in dioxane at 40°C. The characterization of all samples was accomplished by equilibrium ultracentrifugation, vapor-pressure osmometry, viscometry, and gel-permeation chromatography. It is found that the molecular chain of cationically prepared polymer is somewhat branched owing to structural isomerism during polymerization. Isoamyl acetate is found to be a theta solvent for stereo-block as well as for atactic and syndiotactic polymers; the theta temperature is determined as the temperature at which the light-scattering second virial coefficient A2 vanishes. A close correlation is found between the theta temperature and stereoisomerism. The absorbances of the 1154 and 974 cm-1 bands in the infrared spectra decrease with decreasing molecular weight; in addition to the mere existence of alternating CH2 and CH(CH3) groups in the polymer chain, rather long sequences of this type are required for the appearance of these bands. Changes in the absorption band at 997 cm-1 show that chains consisting of over ten isotactically connected monomer units can assume a helical conformation. From the high-resolution NMR spectra of different polypropylenes, including isotactic polymers of low molecular weight, it is found that in estimating the microstructure, account must be taken of the effects of stereoisomerism within tetrads of monomer units on the apparent widths of the methylene proton resonances. If substantial concentrations of several of the possible types of tetrads are present (i.e., if the tactic sequence lengths are quite short), then it is difficult to determine the relative amounts of tactic dyads accurately from the 100 Mcps methylene proton resonances.
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  • 173
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 7 (1969), S. 1669-1679 
    ISSN: 0449-2978
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: A method for evaluating the relaxation time as a function of both temperature and volume from volume contraction experiments, as proposed by Kovacs, was experimentally examined by using monodisperse poly-α-methylstyrene samples of various molecular weights and blends. It was concluded that his theory can be successfully applied to the present experimental data, though his two different approximations give somewhat different values of the shift factor for the time-temperature superposition of volume contraction data. A difference was observed between the temperature dependence of the shift factor of monodisperse polymers and that of blends.
    Zusätzliches Material: 7 Ill.
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  • 174
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 7 (1969), S. 1705-1719 
    ISSN: 0449-2978
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The temperature dependence of relative modulus observed in filled thermoset, thermoplastic, and polyelectrolyte salt matrices is explained on the basis of induced stresses produced by the differences in the thermal expansion coefficients of the constituent materials. The analysis is based on the assumption that the modulus of the matrix in a filled polymer is less than that of the unfilled polymer. The temperature dependence of relative modulus is expressed as a function of the difference in thermal expansion coefficients, the volume fraction, the relative modulus in the unstressed state, and mechanical properties of the phases. Agreement is good between the analysis and experimental results for three systems: epoxy and glass, polyethylene and wollastonite, and a polyelectrolyte salt with mica and asbestos.
    Zusätzliches Material: 7 Ill.
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  • 175
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 7 (1969), S. 1785-1809 
    ISSN: 0449-2978
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Infrared spectroscopic studies have been made of mixed crystals of linear polyethylene and perdeuteropolyethylene. On the basis of normal vibration analyses by Tasumi and Krimm it had been shown that the study of crystal splittings of internal chain modes in such mixed crystals could provide information on the geometry of chain folding. The present results, which include a study of n-paraffin (C36) mixed crystals, confirm these predictions. They show that (110) folding predominates in dilute solution grown crystals, and that this is transformed to (200) folding in melt-crystallized polymer. Folding with adjacent re-entry is favored, a random re-entry model being clearly eliminated.
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  • 176
    ISSN: 0449-2978
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: A modus operandi is developed for determining the molecular structure of hydroxypropylcellulose (HPC), and characterizing, in quantitative terms, the morphological changes occurring when a water-cast film of the polymer is deformed. This involves the application of the following eleven different physical measurements: wide-angle x-ray diffraction, differential scanning calorimetry, density, melt rheometry, infrared spectroscopy, refractive index, birefringence, sonic modulus, small-angle light scattering, optical and electron microscopy. In addition, a computer was utilized as a mathematical diffractometer. Morphologically, water-cast HPC was observed to have structure at all levels, from the molecular to the supermolecular. The HPC molecule has a backbone of anhydroglucose units twisted into an irregular 31 helix. Intramolecular hydrogen bonding of the poly(propylene oxide) side chains leads to a stiff, rodlike molecule. The molecules are packed into microfibrillar crystallites 470 Å long and 34 Å in diameter. The microfibrils in turn, associate into supermolecular rodlike structures. The structural rearrangements that occur at each morphological level during deformation of HPC film are quantitatively examined and described.
    Zusätzliches Material: 36 Ill.
    Materialart: Digitale Medien
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  • 177
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 7 (1969), S. 1329-1355 
    ISSN: 0449-2978
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Mechanical relaxation has been studied at 0.67 cps in linear polyethylene (LPE) and polytetrafluoroethylene (PTFE) between -190 and -20°C. Specimens were prepared by use of various thermal treatments to produce in LPE a range of crystalline fractions from 0.690 to 0.825 and in PTFE from 0.615 to 0.870. An empirical theory is proposed relating the modulus of the crystalline-amorphous composite solid to the moduli and the volume fractions of the two phases. The empirical theory is shown to be in accord with the bounds of Hill and of Hashin and Shtrikman. The theory is used to determine the magnitudes of the crystalline and amorphous components of the low temperature relaxations in LPE and PTFE from measurements of logarithmic decrement and shear modulus. In PTFE the γ relaxation occurs in the amorphous fraction alone. In LPE the γ relaxation is a composite one, formed from the superposition of a small crystal relaxation and a large amorphous relaxation. For the crystal relaxation in LPE the ratio of relaxed to unrelaxed modulus equals 0.78; for the amorphous relaxation, the ratio equals 0.23. In a specimen of LPE with crystal fraction 0.69 the crystal contribution to the relaxation is 25% of the total. The magnitude of the unrelaxed modulus of the crystal fraction of LPE (modulus of polycrystalline LPE at -190°C) is in reasonable agreement with theoretical calculations of Odajima and Maeda.
    Zusätzliches Material: 14 Ill.
    Materialart: Digitale Medien
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  • 178
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 7 (1969), S. 2029-2041 
    ISSN: 0449-2978
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Drawing of single-crystal mats of linear polyethylene has been investigated. Drawing is possible at temperatures higher than about 90°C. The drawing is accompanied by distinct necking, with a large decrease in the thickness of the mat and a very high maximum draw ratio, sometimes over 30. The maximum draw ratio is approximately proportional to the thickness of the lamellae. This behavior strongly suggests the unfolding of chains during drawing. A change of orientation of crystal axes occurs before necking without change of lamellar orientation. The a axis orients in the drawing direction; the b axis orients perpendicular to the direction of drawing; and the chain axis tilts away from the thickness direction of the mat. The structure of films drawn from mats is characterized by a distinct double orientation of crystals. This biaxial orientation in the drawn films has a high degree of correlation with the orientation of crystal axes observed before necking, and suggests that necking takes place in such a way that the chain tilts gradually about the b axis and ultimately unfolds. The postulate of formation of transitory two-dimensional crystals in necking seems useful in explaining the double orientation in the drawn film. The orientation behavior of crystal axes observed before necking is not always similar to that observed in the deformation of a single crystal. The difference is thought to be due to the effect of forces induced by drawing that act in the direction normal to the lamellae within a mat.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
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  • 179
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 7 (1969), S. 1811-1818 
    ISSN: 0449-2978
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: A “dual sorption” model has been proposed by Michaels, Vieth, et al. to explain extensive equilibrium sorption data for several gases in some glassy polymers. To explain data on sorption kinetics, it was further postulated that one of the sorption modes immobilizes the gas molecules. Stated mathematically, this model leads to a modified form of Fick's second law. Both normal and desorption time lags for diffusion have been computed here for this model of diffusion in glassy polymers. The computed time lags are shown to be dependent on the boundary concentrations used in permeation. Experimental measurement of these time lags would be a sensitive and critical test to ascertain the validity of this theory.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
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  • 180
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 7 (1969), S. 1863-1882 
    ISSN: 0449-2978
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Poly(methyl methacrylate) tensile bars were prepared containing nearly spherical polytetrafluoroethylene particles in concentrations from one to a thousand particles per gauge length of the bars. Particle diameters varied from 0.0035 to 0.018 in. Exhaustive tensile tests were performed at sufficiently high strain rate to assure brittle fracture and the results analyzed statistically by the theory of extreme values as proposed by Epstein. The results suggested that the polytetrafluoroethylene particles themselves did not act as flaws, but that they intensified the stress field on natural flaws which acted as the origin of fracture. Assuming a Laplace distribution as the underlying distribution of tensile strength (not to be confused with observed distribution of tensile strengths) gave predicted fracture statistics in good agreement with experiment.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
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  • 181
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 7 (1969), S. 2142-2143 
    ISSN: 0449-2978
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Materialart: Digitale Medien
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  • 182
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 7 (1969), S. 1895-1905 
    ISSN: 0449-2978
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: A simple, practical calculation procedure has been developed for predicting the changes in molecular weight distribution of a polymer undergoing random crosslinking and/or degradation. Simulations of the random crosslinking and degradation of narrow and broad Poisson-type distributions have been made. The results agree with those calculated from Kimura's analytical solutions to Saito's general equations after a correction has been made for a mathematical error in Kimura's solution. This method can be applied to determining the probabilities of crosslinking and scission for any arbitrary molecular weight distribution expressed in tabular form. The importance of using narrow distribution samples to estimate crosslinking from changes in molecular weight distribution is graphically demonstrated.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
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  • 183
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 13 (1969), S. 1993-2006 
    ISSN: 0021-8995
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: Shear properties of commercially available polystyrenes with narrow molecular weight distribution have been measured in the transition region from 100°C to 150°C and over a frequency range from 50 Hz to 1000 Hz. The effect of molecular weight or shear properties is established with four polymers ranging in molecular weight from 20,000 to 860,000. A broad, bimodal distribution is also studied. The properties of these polymers, with two different diluents added, illustrate the rather marked qualitative difference in effects caused by diluents.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
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  • 184
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 13 (1969), S. 1949-1963 
    ISSN: 0021-8995
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: The structure of the cyclic urea influenced the rate of reaction with cotton cellulose and the mechanism by which reaction occurred. Reaction of N, N′-dimethylolethylene-urea (DMEU) and N, N′-dimethylolpropyleneurea (DMPU) with cellulose in presence of inorganic salt catalysts proceeded through methylol hydroxyls and at the same rate; but reaction mechanism differed. With DMEU, N → metal ion coordination occurred and SN2 mechanism prevailed. With DMPU, O → metal ion coordination resulted.Reaction of dihydroxyethylene urea (DHEU), N, N′-dimethyldihydroxyethyleneurea (DMeDHEU), and N, N′-dimethyloldihydroxyethyleneurea (DMDHEU) with cotton cellulose proceeded through ring hydroxyls with the formation of a carbonium ion, indicating an SN1 mechanism. The much faster rate of reaction with DMeDHEU than with DHEU was attributed to the more electronegative environment of its ring hydroxyl, while the much slower rate of reaction of DMDHEU was attributed to hydrogen bonding between its methylol and ring hydroxyls.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
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  • 185
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 13 (1969), S. 2031-2032 
    ISSN: 0021-8995
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 186
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 13 (1969), S. 17-22 
    ISSN: 0021-8995
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: Recently, Chien and Boss calculated rate constants for the autoxidation of isotactic polypropylene based upon a postulated relatively simple scheme. Electron spin resonance, volumetric, and chemical techniques were employed. It behooved the authors of this paper to demonstrate that similar values of these rate constants could also be calculated from a more general scheme. From this general scheme, expressions were derived which involved the rate constants of interest and other constants which had been previously calculated from experimental data based upon the use of infrared absorption techniques. The values of our calculated rate constants at various temperatures agreed well with those reported by Chien and Boss where comparison was possible.
    Zusätzliches Material: 3 Tab.
    Materialart: Digitale Medien
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  • 187
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 13 (1969), S. 23-27 
    ISSN: 0021-8995
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: The authors had previously reported a general scheme with corresponding kinetic expressions for the uncatalyzed thermal autoxidation of polyolefins, such as atactic polybutene-1 (APB), in the bulk phase. Recently, Bawn and Chaudhri reported that similar kinetic expressions and scheme were also applicable to autoxidation of atactic polypropylene (APP) in solution. These workers did not attempt to correlate their results for the effect of oxidation on the molecular weight of APP as evidenced by intrinsic viscosity. In this paper, we have applied expressions, previously reported for changes in intrinsic viscosity as a function of time during the autoxidation of APB in the bulk phase, to the data provided by Bawn and Chaudhri for the autoxidation of APP in solution. The quantitative evidence obtained indicates that the intrinsic viscosity relationships which were found to be valid for the autoxidation of APB in the bulk phase are also valid for the autoxidation of APP in solution (at polymer concentrations of ca. 1.5M and above).
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
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  • 188
    ISSN: 0021-8995
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: The products obtained on degradation of poly(m-aminostyrene) in vacuo are described. The effect of molecular weight and pyrolysis temperature are discussed and the behavior of poly(m-aminostyrene) compared with that of polystyrene. Quantitative analytical methods using ultra-violet spectroscopy and gas liquid chromatography are described for m-aminostyrene and m-toluidine. The possible mechanisms of degradation to yield the products are discussed.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
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  • 189
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 13 (1969), S. 2073-2084 
    ISSN: 0021-8995
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: The pyrolysis of acrylic fiber up to 400°C in an inert atmosphere at 1° and 6°C/min was studied by means of thermogravimetric and differential thermal analysis. The exothermic reaction occuring at 180-300°C was shown to be due to the reaction of nitrile groups by comparing the extent of exotherm with the number of nitrile groups present, determined by infrared spectroscopy. In addition, results of single-fiber tensile measurements, density, and elemental analysis of the pyrolyzed fibers are interpreted in terms of possible molecular structures. The gases evolved on pyrolysis were analyzed for both ammonia and hydrogen cyanide and the liberation of ammonia was attributed to a termination reaction of the polymerization of nitrile groups. The critical conditions necessary for the production of high strength and modulus carbon fiber are discussed briefly in ralation to the chemical changes occurring on pyrolysis.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
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  • 190
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 13 (1969), S. 2119-2127 
    ISSN: 0021-8995
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: The properties of crosslinked thermosetting resins depend markedly on the completeness of the crosslinking process. Determination of the degree of cure of an unsaturated polyester resin has been studied previously by mechanical, spectroscopic and volume resistivity methods. In this respect the effect of cure time and temperature on the ac dielectric constant and dissipation factor at 1 kc/s and 10 kc/s is considered. The dissipation factor appears to be a most useful parameter for detecting changes in the degree of cure in the later stages of reaction.The electrical properties of the cured resin are discussed, and values for the energy of activation for electrical conduction are compared with literature reports on similar materials.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
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  • 191
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 13 (1969), S. 2183-2191 
    ISSN: 0021-8995
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: Polysulfone, polycarbonate, and phenoxy resins were aged under thermal and ultraviolet light conditions. Thermoxidative processes in polysulfone and polycarbonate are of such minor significance as not to impart noticeable losses in these materials below 125°C. In phenoxy, however, thermal oxidation above 100°C results in rapid deterioration of all physical properties. This probably results from the low glass transition temperature of this polymer. Photo-oxidation rapidly degrades polysulfone. This appears to be a consequence of scission at the sulfone link. In polycarbonate, however, the only serious result of short-term irradiation is discoloration. For phenoxy resin, crosslinking through reactions at the hydroxyl group is the principal result of photo-oxidation. In all processes the bisphenol A portion of the three polymers appears to play only a small role.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
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  • 192
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 13 (1969), S. 2209-2221 
    ISSN: 0021-8995
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: The difficulties involved in the measurement of the partition coefficient and diffusion coefficient of NaCl in hydrophilic polymer membranes are examined by the initial rate and late-time analysis of desorption data for three nonionic polymer systems. The late-time analysis, based on the plot of the logarithmic relative desorption versus time, was found to be useful when the diffusion is Fickian and the magnitude of D2/l2 is small. Depending on the magnitude of D2/l2, an accurate measurement of k2 and determination of D2 cannot be achieved without correction for the effect of surface salt solution, impossible with late-time analysis. The initial rate measurement was found more versatile for general non-Fickian diffusion and it gave a means of correction of the errors involved in estimating the partition coefficient. In general, the diffusion of NaCl in hydrophilic polymers is not ideal Fickian and the discrepancy between the two analyses is appreciable.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
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  • 193
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 13 (1969), S. 2235-2245 
    ISSN: 0021-8995
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: Poly(vinyl chloride) displays a normal DSC of DTA curve for the glass transition when quenched from above its Tg. However if cooled slowly or annealed near the glass transition temperature, a peak appears on the DSC or DTA curve at the Tg. In this paper quantitative studies of the time and temperature effects on the production of this endothermal peak during the annealing of PVC homopolymer and an acetate copolymer are presented. The phenomenon conforms to the Williams, Landell, and Ferry equation for the relaxation of polymer chains, the rate of the peak formation becoming negligible at more than 50°C below Tg. The energy difference between the quenched and annealed forms is small. For a PVC homopolymer annealed 2 hr at 68°C, which is Tg -10°C, the difference is 0.25 cal/g. For a 13% acetate copolymer of PVC similarly annealed, the difference is 0.36 cal/g. The measured rates of the process give a calculated activation energy of 13-14 kcal/mole for PVC homopolymer and copolymer. This appearance of a peak on the Tg curve for a polymer when annealed near the glass temperature appears to be a general phenomenon.
    Zusätzliches Material: 6 Ill.
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  • 194
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 13 (1969), S. 2269-2276 
    ISSN: 0021-8995
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: Monosodium 1-glutamate, disodium inosine-5′-monophosphate, disodium guanosine-5′-monophosphate, calcium d-pantothanate, 1-arginine, and 1-aspartic acid were found to protect the changes in the internal relationships of the atoms in the protein molecule from radiation damage. The behavior of the optical rotation was determined. The empirical equation for the protective effect is given by [α] f = b - a log X, where [α] f is the final specific rotation of the solution, X is the concentration of the amino acids, and a and b are adjustable constants.
    Zusätzliches Material: 12 Ill.
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  • 195
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 13 (1969), S. 2297-2311 
    ISSN: 0021-8995
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: The load-compression behavior of a foam reflects its geometric structure and the physical properties of the matrix polymer. Quantitative relations between these parameters have been established in the present study. Based on both theoretical analyses and experimental data obtained on a flexible polyurethane foam, it is shown that the compressive stress can be factored into the product of two terms: (1) a dimensionless function of the compressive strain, ψ(ε), calculated from experimental load-compression data and reflecting the buckling of the foam matrix; and (2) a factor, εEf, where Ef is the apparent Young's modulus of the foam (which is a function primarily of the modulus of the base polymer E0 and of the volume fraction of polymer, ϕ). Thus the compressive stress behavior of a foamed polymer is determined by E0, ϕ, and the matrix geometry, the latter described by the function ψ(ε). Using these established relations, it now is possible to delineate precisely the structural features a foam must possess - density, cell shape and size distribution, and modulus of the base polymer - to meet a given load-compression specification.
    Zusätzliches Material: 12 Ill.
    Materialart: Digitale Medien
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  • 196
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 13 (1969), S. 2325-2332 
    ISSN: 0021-8995
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: Poly(α,α,α′,α′-tetrafluoro-p-xylylene) was prepared by the pyrolysis of cyclo-di-(α,α,α′,α′-tetrafluoro-p-xylylene) and by the pyrolysis of α,α′-bis(alkylsulfonyl)-α,α,α′,α′-tetrafluoro-p-xylene. The pyrolysis of α,α′-dibromo-α,α,α′,α′-tetrafluoro-p-xylylene also gave the polymer, but the method is less satisfactory. Poly(α,α,α′,α′-tetrafluoro-p-xylylene) shows remarkable thermal and oxidative stability at elevated temperatures. Useful mechanical and electrical properties are retained after aging for 3000 hr at 250° in air. After initial change due to crystallization, tensile strength remains near 10,000 psi, elongation above 5%, and dielectric constants and dissipation factors at approximately 2.4 and .001, respectively.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
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  • 197
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 13 (1969), S. 2359-2369 
    ISSN: 0021-8995
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: The use of a single detector in gel permeation chromatography (GPC) for samples of varying composition leads to erroneous conclusions. With certain simplifying assumptions, a gel permeation chromatograph equipped with properly selected dual detectors yields composition and molecular weight distribution information that is meaningful. Examples discussed are a mixture of homopolymers and a sample supposed to have been a styrene-butadiene block copolymer. The ultraviolet absorption is used in conjunction with the refractive index trace to give qualitative information that is much more informative than could be obtained with one detector. Calibration of the relative responses of the detectors to each of the components of the mixture is described, and these calibrations are used to calculate point-by-point composition, molecular weights, and molecular weight averages.
    Zusätzliches Material: 6 Ill.
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  • 198
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 13 (1969), S. 2397-2409 
    ISSN: 0021-8995
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: The proper use of the method for correcting instrumental spreading in GPC requires a precise calibration of the spreading characteristics of the instrument. Heretofore, such a calibration could be obtained only through the tedious reverse-flow experiments. A more rapid method of calibrating instrumental spreading is presented in this work. This method uses the leading halves of the chromatograms of several standard polystyrene samples. These chromatograms are normally used in the calibration of molecular weight; additional experimental steps are therefore not required. The calculation of the instrumental spreading characteristics from these chromatograms is also relatively simple. The instrumental spreading characteristics were found to depend on the elution volume but not on the nature of the polymer. Thus, calibration results from using polystyrene standards can be used to treat chromatograms for other polymers. For the present GPC instrument, the spreading was found to reach a maximum at an elution volume near 400,000 in polystyrene molecular weight. The existence of this maximum is in agreement with observations made by other investigators and is and indication that diffusion in the mobile phase is not an important contribution to instrumental spreading. The problem of skewing or tailing is discussed. Indication of skewing was observed for one of the higher molecular weight polystyrene samples but the extent of skewing was not severe at the present flow rate of 2 ml/min.
    Zusätzliches Material: 5 Ill.
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  • 199
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 13 (1969), S. 149-168 
    ISSN: 0021-8995
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: Telechelic elastomers, polymers with reactive terminal groups, can be prepared in emulsion and solution systems. Examples of characterization of the polymers and preparation of a mercapto telechelic copolymer in an emulsion system and of mercapto-, hydroxy-, and aziridinyl-telechelic elastomers in solution systems are given. The elastomers were cured in peroxide or sulfur-accelerator formulations. The telechelic polymers exhibited enhanced stress-strain and dynamic properties in comparision to those of the controls. In tread formulations, outstanding properties were obtained for the mercapto-and azieridinyl-telechelic butadiene-styrene copolymers.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 200
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 13 (1969), S. 193-203 
    ISSN: 0021-8995
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: Noncrosslinked copolymers of hydroxyethyl methacrylate (HEMA) with ethyl methacrylate (EMA) were prepared and investigated as candidate materials for reverse osmosis membranes. Water and salt flux were calculated from the results of osmosis experiments, compared with cellulose acetate and found to be somewhat smaller. The mobility of water varies by several orders of magnitude between a high flux cellulose acetate membrane and a low flux HEMA-EMA membrane.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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