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  • Chemical Engineering  (10)
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  • 1
    Electronic Resource
    Electronic Resource
    Transition behavior and phase segregation in TDI polyurethanesPresented part at the American Chemical Society Meeting. Philadelphia (1975). (1977)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 17 (1977), S. 73-80 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Prior studies of two series of segmented polyurethanes based on 2, 4 toluene cliisocyanate (2, 4 TDI) or 2, 8 TDI, butanediol, and a 1000 molecular weight polytetramethyleneoxide (PTMO-1000) soft segment revealed a rapid increase in soft segment glass transition temperature (Tg) with increasing urethane content in the 2, 4 TDI series. The change in Tg couldbe correlated with estimates of hard segment-soft segment phase mixing obtained by infrared analysis of the urethane NH and carbonyl bands. In the present paper, the infrared data have been reevaluated using improved procedures for resolving the carbonyl band into H-bonded and nonbonded components, and the relation between the estimated extent of phase mixing and Tg has been reexamined. The transition behavior in an extensive series of related polymers has also been determined, including 2, 4 TDI arid 2, 6 TDI samples with PTMO2000 as well as polybutyleneadipate (PBA-1000 and PBA-2000) soft segments. The results indicate the effectiveness, of increased soft segment molecular weight in promoting phase segregation, imply that much greater phase mixing occurs in polyester than polyether samples, suggest that anchoring the ends of the soft segments has only a small effect on Tg, and provide some evidence that H-bonding not only increases Tg but can also impede soft segment crystallization.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760170203
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  • 2
    Electronic Resource
    Electronic Resource
    Structural and mechanical properties of polybutadiene-containing polyurethanes (1981)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 21 (1981), S. 163-171 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A series of segmented polyurethanes based on hydroxylterminated polybutadienes (HTPBD) and their hydrogenated derivatives (HYPBD) has been synthesized. Thermal, mechanical, and spectroscopic studies were carried out over a wide temperature range to elucidate the structure-property relationships existing in these polymers. Both thermal and dynamic mechanical response showed a soft segment Tg at -74°C for the unsaturated polyurethanes and at -69°C for the hydrogenated samples. In addition, two hard segment transitions are observed by differential scanning calorimetry (DSC) at 40 and 75°C and a softening region by thermal mechanical analysis (TMA) at 190°C. The low Tg, very close to that of the free HTPBD and HYPBD and independent of hard segment content, indicated that these polymers were well phase separated. Results of infrared analysis revealed that at room temperature, 90-95 percent of the urethane N-H groups formed hydrogen bonds. Since hydrogen bonding resides only within the hard segment domain in these butadiene-containing polyurethanes the extent of H-bonding served as additional evidence for nearly complete phase segregation. From dynamic mechanical studies, the plateau modulus above the soft segment Tg and stress-strain behavior depended upon the concentration of hard segments. A slight increase in the modulus, a moderate increase in stress (σb), and decrease in elongation accompanied a higher hard segment content. The thermal and mechanical response of these polyurethanes appears to be consistent with behavior observed for other phase segregated systems. Variations in behavior resulting from hydrogenation of the precursor prepolymer are discussed.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760210309
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  • 3
    Electronic Resource
    Electronic Resource
    Thermal transition behavior of polybutadiene containing polyurethanes (1979)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 19 (1979), S. 1122-1128 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The thermal transition behavior of a series of hydroxy terminated polybutadiene (HTPBD) containing segmented polyurethanes has been studied by differential scanning calorimetry (DSC) and thermal mechanical analysis (TMA). Four transition regions are observed; the soft segment Tg, at -74°C, two hard segment transitions T1, at 40°C and T2 at 103°C and a softening region by TMA at 180°C, presumed to arise from the dissociation of allophonate bonding, The low Tg, only 7°C higher than the Tg of free HTPBD, indicates nearly complete phase segregation despite the amorphous nature of the hard segment structure. The dependence of T1, on hard segment length and thermal cycling suggests that it represents domains consisting primarily of shorter hard segments units. Factors contributing to the rather low mechanical properties of HTPBD polyurethanes are also discussed.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760191510
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  • 4
    Electronic Resource
    Electronic Resource
    Low temperature dynamic mechanical properties of polyurethane-polyether block copolymers (1972)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 12 (1972), S. 25-29 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Dynamical mechanical relaxation spectra of a number of polyurethane-polyether block copolymers have been studied as a function of composition, temperature and frequency. At low temperatures these copolymers are characterized by a high glass-like modulus which decreases to a much lower typically elastomeric value in a narrow temperature range. The latter is a function in certain cases of the composition of the polymer. The rubbery plateau is maintained up to at least 140°C. In addition, a secondary relaxation is observed around -130°C. These observations can be interpreted in terms of an overall structure consisting of a polyether matrix containing segregated polyurethane domains, the latter serving as physical crosslinks in the system at ambient temperatures and above.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760120104
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  • 5
    Electronic Resource
    Electronic Resource
    DSC and TBA studies of the curing behavior of two dicy-containing epoxy resins (1979)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 19 (1979), S. 304-312 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The curing behavior of two commercial dicy-containing resins (I & II), both with recommended cures of 127°C/2 h, has been studied by differential scanning calorimetry (DSC), torsional braid analysis (TBA) and Fourier Transform infrared spectroscopy. Compositional analysis reveals that the two resins differ primarily in the amine/epoxy ratio and the nature of the main epoxy components. Factors contributing to the complex curing behavior observed with II are identified. Isothermal kinetic runs by DSC and TBA lead to estimates for the conversion at the gel point, and to results which suggest that the reactions of epoxy with amine and hydroxyl occur with similar activation energies and similar heats of reaction.
    Additional Material: 15 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760190413
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  • 6
    Electronic Resource
    Electronic Resource
    A dynamic mechanical study of the curing reaction of two epoxy resins (1979)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 19 (1979), S. 313-318 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The curing behavior of two commercially formulated epoxy resins composed of the tetrafunctional amine dicyandiamide and with differing epoxy components, 4,4′-bisglycidylphenyl-2,2′-propane and the tetraglycidyl ether of methylene dianiline, is characterized by dynamic spring analysis. This supported viscoelastic technique is well suited to the determination of the onset of gelation under isothermal conditions but the method is not useful for monitoring later stages of reaction when the resins become more rigid. The activation energy for the curing of the two resins is about 87 kJ/mole (20.7 kcal/mole). Rate constants for the first order curing reaction are given. Additional studies of films cured below the ultimate Tg show that two relaxations can be observed upon heating. The first relaxation occurs near the original isothermal cure temperature with a low activation energy, about 250 kJ/mole, whereas the second relaxation occurs near the ultimate Tg, under the conditions used here, with an activation energy of 500-650 kJ/mole. It is believed that these activation energies provide a unique method of characterizing the molecular mobility of epoxy resins at various states of cure.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760190414
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  • 7
    Electronic Resource
    Electronic Resource
    Thermal and mechanical properties of linear segmented polyurethanes with butadiene soft segments (1981)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 21 (1981), S. 668-674 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A series of segmented polyurethanes based on a hydroxyl terminated polybutadiene soft segment (HTPBD) have been prepared with varying hard segment content between 20 and 60 weight percent. These materials are linear and amorphous and have no potential for hydrogen bonding between the “hard” and “soft” segments. The existence of two-phase morphology was deduced from dynamic mechanical behavior and thermal analysis. Both techniques showed a soft segment glass transition temperature, Tgs, at -56°C and hard segment transitions between 20 and 100°C, depending on the urethane content. The low value of Tg, only 8° higher than the Tg of free HTPBD and independent of hard segment concentration indicated nearly complete phase segregation. Depending on the nature of the continuous and dispersed phases, the urethanes behaved as elastomers below 40 weight percent hard segment or as glasslike materials at higher hard segment contents. The effect of thermal history on transitions of the HTPBDurethanes was also investigated and the results suggest that the absence of hydrogen bonding to the soft segment must account for the extraordinary insensitivity to thermal history in dynamic mechanical, thermal and stress-strain behavior. Comparisons are made to the more common polyurethanes containing polyether and polyester soft segments.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760211108
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  • 8
    Electronic Resource
    Electronic Resource
    Liquid sorption in a segmented polyurethane elastomer (1986)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 26 (1986), S. 1547-1551 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The sorption and diffusion of a series of liquids in a segmented polyurethane have been studied to determine how the behavior is affected by the choice of solvent and the heterophase nature of the polymer. The polyurethane was composed of methylene-di-para-phenylene isocyanate (MDI) butanediol, and poly(tetramethylene oxide) (1000) with a mole ratio 3:2:1. Immersion experiments in n-heptane liquid, a poor solvent, and incremental sorption experiments in n-heptane vapor showed normal Fickian havior. In the set of liquids of increasing polarity, which included 1-chloroheptane, three dichloroalkanes and orthodichlorobenzene, the swelling increased to very high levels. Effective values of the molecular weight between crosslinks computed from the Flory Rhener equation, assuming complete phase segregation, varied widely with the different liquids. Agreement could be improved by allowing 30 percent mixing of hard segments with the soft segment phase. The sorption and desorption curves for the highly swelling liquids showed various anomalies some of which might be the result of solvent induced relaxation of hard segment domains.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760262204
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  • 9
    Electronic Resource
    Electronic Resource
    TBA studies of prepreg curing behavior (1980)
    Brookfield, Conn. : Wiley-Blackwell
    Polymer Composites 1 (1980), S. 97-102 
    Details
    ISSN: 0272-8397
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The torsional braid analysis (TBA) equipment has been used as an automated torsion pendulum to characterize prepreg materials in the form of single ply strips (2-1/2 × 1/8 in.). Compared to the use of coated glass braids, the main difference was a marked weakening of the gelation mechanical damping peak in isothermal runs. However, prepreg materials consisting of epoxy resins on glass, carbon or aramid fibers were successfully run isothermally to provide gelation and vitrification times as a function of temperature, or in constant heating rate scans to reveal the T 〈 Tg and the Tg relaxations of the uncured resins, and at higher temperatures phenomena associated with gelation, vitrification and devitrification.
    Additional Material: 17 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pc.750010209
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  • 10
    Electronic Resource
    Electronic Resource
    Effects of variation in composition and temperature on the amine cure of an epoxy resin model system (1983)
    Brookfield, Conn. : Wiley-Blackwell
    Polymer Composites 4 (1983), S. 206-213 
    Details
    ISSN: 0272-8397
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Prior liquid chromatographic studies have shown that the reactions in epoxy resin model system phenyl glycidyl ether, p-chloroaniline, and Monuron include amine addition to epoxy, homopolymerization of the epoxy, and a chain-transfer reaction involving the hydroxy groups of the addition products. The present work examines the effect of variation in concentration of the accelerator Monuron, the amine-to-epoxy ratio, and the temperature on the competitive reaction mechanisms. The fraction of phenyl glycidyl ether reacting by homopolymerization increases with accelerator concentration and decreases with increasing amine-to-epoxy ratio and increasing temperature. The estimated contribution from chain transfer is much smaller and appears to parallel the homopolymerization reaction, as might be expected.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pc.750040403
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