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  • 1
    Digitale Medien
    Digitale Medien
    The physical ageing of amorphous poly(hydroxybutyrate) (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Polymer International 39 (1996), S. 221-229 
    Details
    ISSN: 0959-8103
    Schlagwort(e): polyhydroxybutyrate ; copolymers ; embrittlement ; physical ageing ; enthalpic relaxation ; crystallisation ; DSC ; DMTA ; DETA ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: The embrittlement of poly(hydroxybutyrate), and its copolymers with hydroxyvalerate, on storage at room temperature has been considered in the light of the relaxation of the interlamellar glassy regions and also the development of secondary crystallisation. From a study of the kinetics of the two processes, the first mechanism has been eliminated particularly since the glass transition, as measured by dielectric thermal analysis (DETA), was below room temperature.Control of the primary crystallisation of PHB was observed to reduce the extent of the development of secondary crystallisation and to eliminate the embrittlement on storage. DMTA and DETA were found to be useful techniques for measuring the mobility of the amorphous regions in partially crystalline samples, under conditions where DSC was unable to detect any glass transition.
    Zusätzliches Material: 13 Ill.
    Materialart: Digitale Medien
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  • 2
    Digitale Medien
    Digitale Medien
    Dielectric and dynamic mechanical relaxation studies on poly(aryl ether ketone)s (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 851-859 
    Details
    ISSN: 0887-6266
    Schlagwort(e): poly(aryl ether ketone)s ; dielectric relaxation spectroscopy ; dynamic mechanical analysis ; α-relaxation ; β-relaxation ; Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The relaxation behavior of four amorphous poly(aryl ether ketone)s was investigated using dielectric relaxation spectroscopy and dynamic mechanical analysis. The temperature dependence of the relaxation times of the glass transition process and the cooperative nature of this process were unaffected by changes in polymer structure. The temperature location of the loss peaks for all polymers progressed smoothly between the low frequency of the mechanical measurements and the higher frequencies of the dielectric probe. Differences were observed in mechanical activation energy and dielectric relaxation strength for one polymer which contained a significant concentration of meta linkages, compared with the para-linked polymers, while relaxation broadness was generally greater in the dynamic mechanical mode. Changes in chemical structure had little effect on the shape, intensity, and location of the β-relaxation peak, the main observation being that the Arrhenius activation energy measured by dynamic mechanical analysis was significantly higher than that calculated from the dielectric data. The dielectric β-relaxation was sensitive to absorbed moisture. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 851-859, 1998
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
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  • 3
    Digitale Medien
    Digitale Medien
    Study of the thermal effects in the necking of polymers with the use of an infrared camera (1980)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 18 (1980), S. 2169-2179 
    Details
    ISSN: 0098-1273
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: When a polymer specimen yields under tension by the process of cold-drawing, heat is generated in the necking region. This beating effect has been studied in polycarbonate, polyethylene, polypropylene, and PVC with the use of a thermovision system which produces a real time thermal image of the necking specimen. In this way it was possible to observe the temperature distribution over the surface of the neck and to show that at least 85% of the mechanical work done on the specimen during necking was converted into heat. A semiempirical equation relating the maximum temperature to the drawing rate has been derived.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pol.1980.180181102
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  • 4
    Digitale Medien
    Digitale Medien
    The effect of density on the properties of high molecular weight polyethylenes (1977)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 15 (1977), S. 1077-1088 
    Details
    ISSN: 0098-1273
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Ultrahigh molecular weight polyethylene has been crystallized at various pressures (0-330 MN m-2) to material of a wide range of specific gravities (0.928-0.967). Tensile measurements illustrate that the properties of these materials are dependent on specific gravity (sg), in that the yield stress increases linearly with sg. Low sg (0.928-0.944) materials exhibit higher yields stress than low molecular weight materials of the same sg but the opposite is true for higher sg material. Low sg material also extends uniformly after yielding while above a sg of 0.944 necking becomes more marked. Orientation hardening is observed with all these materials above 200% extension and is more marked than with low molecular weight polymers. Differential scanning calorimetry (DSC) analysis of the pressure crystallized materials indicate that in the range 200-400 MN m-2 two phases are present, i.e., chain-folded and chain-extended lamellas. Increasing or decreasing the pressure changes the crystalline component to chain-extended or chain-folded morphologies, respectively. The reorganization of the crystalline components on drawing is discussed.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pol.1977.180150614
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  • 5
    Digitale Medien
    Digitale Medien
    On a nonexponential transformation equation for spherulitic crystallization (1978)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 16 (1978), S. 81-89 
    Details
    ISSN: 0098-1273
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: An equation has been derived for the development of crystallinity from heterogeneously nucleated spherulites which impinge with a small number of neighboring but randomly centered spherulites. The crystallization-time dependence calculated from the equation conforms to an Avrami equation with initial fractional values for the n exponent, and the equation appears to be a better fit of the initial time dependence of the crystallization of polyethylene than the Avrami equation itself. It appears to account satisfactorily for the observation of fractional n values in the analysis of the crystallization curves of this polymer. The derivation of the equation only accounts for the impingement of spherulites in pairs and does not allow for multiple impingements. This limits its fit to less than the total primary crystallization. The effect on nonrandom centering of spherulites is discussed.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pol.1978.180160107
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  • 6
    Digitale Medien
    Digitale Medien
    Dehydrochlorination reactions in polymers. Part III. Vinylidene chloride-styrene copolymers (1968)
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-1: Polymer Chemistry 6 (1968), S. 951-962 
    Details
    ISSN: 0449-296X
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A systematic study of the effect of styrene units on the thermal stability of vinylidene chloride copolymers was made. In general, the copolymers were more easily dehydrochlorinated than the homopolymer. The copolymers eliminate HCl at rates that could only be interpreted in terms of styrene group activation. However, the elimination rate fell too rapidly with reaction extent to be accounted for by concentration changes or weak links and was consistent with retardation by the reaction products. The elimination was a radical process and accompanied by chain scission and crosslinking in competition.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pol.1968.150060424
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  • 7
    Digitale Medien
    Digitale Medien
    Polymerization of butadiene initiated by the 1:1 chelate of n-butyllithium and N,N,N′,N′-tetramethylethylenediamine (1972)
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-1: Polymer Chemistry 10 (1972), S. 3451-3456 
    Details
    ISSN: 0449-296X
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Evidence is given for the species involved in the initiation and propagation steps in the polymerization of butadiene with n-butyl lithium: tetramethylethylene diamine (TMEDA) as being the monomeric butyl lithium and the solvated ion pair, (A), respectively. Species A is also produced on the metalation of polybutadiene with butyl lithium: TMEDA.
    Zusätzliches Material: 2 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pol.1972.170101201
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  • 8
    Digitale Medien
    Digitale Medien
    Dehydrochlorination reactions in polymers. Part II. Chlorinated polystyreneFor Part 1 of this series, see Burnett et al.1 (1967)
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-1: Polymer Chemistry 5 (1967), S. 2297-2310 
    Details
    ISSN: 0449-296X
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The dehydrochlorination of chlorinated polystyrene was studied in the temperature range 120-220°C., when HCl was the sole volatile product. The dehydrochlorination was accompanied by the slow development of color and chain scission. The elimination rate fell too rapidly with reaction extent to be accounted for by reduction of reagent. Solution studies in o-dichlorobenzene indicated that the reaction was initially first-order in polymer concentration but was retarded by the polyene reaction products. The overall elimination was interpreted as a radical process in which the product was an active retarder. These observations are also valid for the elimination of HBr from brominated polystyrene.
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pol.1967.150050909
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  • 9
    Digitale Medien
    Digitale Medien
    Thermal reactions of polyacrylonitrile (1968)
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-1: Polymer Chemistry 6 (1968), S. 2127-2135 
    Details
    ISSN: 0449-296X
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The exothermic process which occurs on heating polyacrylonitrile above 200°C. is studied with a differential scanning calorimeter and by following volatiles production. The process is associated with coloration of the polymer and the production of ammonia. It is not due to chain scission degradation, which occurs in this temperature range and also produces volatiles.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pol.1968.150060810
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  • 10
    Digitale Medien
    Digitale Medien
    Study of the thermal dehydrochlorination of poly(vinylidene chloride) and poly(vinyl chloride) by ESR spectroscopy (1970)
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-1: Polymer Chemistry 8 (1970), S. 1201-1212 
    Details
    ISSN: 0449-296X
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The evidence for a radical elimination of hydrogen chloride during the thermal degradation of homopolymers and copolymers of vinylidene chloride is summarized and confirmed by an ESR spectroscopic study of the degradation residues. However, sufficient differences in the degradation characteristics exist between these polymers and those of vinyl chloride to suggest that a radical process alone is not sufficient. No evidence of a radical process can be obtained from an ESR spectroscopic analysis of the elimination. The paramagnetic character of the degraded polymer is attributed to the polyene structure produced on dehydrochlorination.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pol.1970.150080513
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