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  • 11
    Electronic Resource
    Electronic Resource
    Interactions of a liquid crystalline polymer with polycarbonate and poly(ethylene terephthalate) (1997)
    Springer
    Journal of materials science 32 (1997), S. 3961-3970 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Thermal behaviour of blends of a liquid crystalline copoly(ester amide) (Vectra B950) with two isotropic polymers has been studied by differential scanning calorimetry. One of the isotropic polymers is an amorphous polymer – polycarbonate, the other is a semi-crystalline polymer – poly(ethylene terephthalate). It was found that the glass transition temperature of polycarbonate decreases with increasing Vectra concentration in the blend, suggesting a partial miscibility between the Vectra liquid crystalline polymer (LCP) and polycarbonate. The miscibility is enhanced through heat treatment at elevated temperatures presumably due to a transesterification reaction. Moreover, the presence of the amorphous poly- carbonate hinders the crystallization of the liquid crystalline polymer in the blends. It was also observed that heat treatment of the Vectra LCP and poly(ethylene terephthalate) blends causes a loss in crystallinity and shifts in transition temperatures of poly(ethylene terephthalate), indicating that exchange reactions occur between Vectra B950 and poly(ethylene terephthalate). Based on these results, a new strategy, in situ compatibilization, is proposed to improve the interfacial adhesion between an LCP and an isotropic polymer.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018673001252
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  • 12
    Electronic Resource
    Electronic Resource
    Toughening mechanisms in a multi-phase alloy of nylon 6,6/polyphenylene oxide (1989)
    Springer
    Journal of materials science 24 (1989), S. 1447-1457 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Toughening mechanisms in a nylon 6,6/polyphenylene oxide (PA/PPO) alloy are studied. This alloy consists of well dispersed PPO particles (containing an elastomeric phase) in a PA matrix. Both crazing and shear yielding mechanisms are found to be sequentially operative in this alloy. When a crack propagates in the material, a crazed zone forms ahead of the crack tip. This crazed zone then transforms into a shear yielded zone as the crack propagates through it. The crazes inside the original crazed zone are closed or distorted by the shear yielding process. In the transformed region, the shear yielded material is oriented at different angles as the crack propagates. These findings are consistent with the notion that hydrostatic tension has to be dissipated in order for the remaining deviatoric stress to reach the critical value for yielding. It is possible to partially attribute the increase in toughness to both crack blunting and zone shielding mechanisms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00553180
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  • 13
    Electronic Resource
    Electronic Resource
    Toughening mechanisms in a multi-phase alloy of nylon 6,6/polyphenylene oxide (1989)
    Springer
    Journal of materials science 24 (1989), S. 1447-1457 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Toughening mechanisms in a nylon 6,6/polyphenylene oxide (PA/PPO) alloy are studied. This alloy consists of well dispersed PPO particles (containing an elastomeric phase) in a PA matrix. Both crazing and shear yielding mechanisms are found to be sequentially operative in this alloy. When a crack propagates in the material, a crazed zone forms ahead of the crack tip. This crazed zone then transforms into a shear yielded zone as the crack propagates through it. The crazes inside the original crazed zone are closed or distorted by the shear yielding process. In the transformed region, the shear yielded material is oriented at different angles as the crack propagates. These findings are consistent with the notion that hydrostatic tension has to be dissipated in order for the remaining deviatoric stress to reach the critical value for yielding. It is possible to partially attribute the increase in toughness to both crack blunting and zone shielding mechanisms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02397085
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  • 14
    Electronic Resource
    Electronic Resource
    The preparation and morphology of PPO-epoxy blends (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 48 (1993), S. 1051-1060 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    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: Poly(phenylene oxide) (PPO) was found to be miscible in diglycidyl ether of bisphenol A (DGEBA) based epoxy. The PPO-DGEBA system exhibited upper critical solution temperature (UCST) behavior. The cloud point temperatures were measured and found to be sensitive to the mol wt of the epoxy resin. A series of PPO-modified epoxies were cured with piperidine at 160°C, which is above the cloud point temperature. Upon cure, two phase solids were formed, which contained discrete PPO particles. However, the two-phase particulate morphology was not uniform and numerous large, occluded PPO particles were observed. In order to improve the uniformity, several styrene-maleic anhydride copolymers were evaluated as potential surfactants for PPO-DGEBA bends. The formation of a uniform, particulate morphology was facilitated by the addition of a styrene-maleic anhydride copolymer, containing a 10:1 ratio of styrene to maleic anhydride. To our knowledge, this is the first time that an emulsifying agent has been added to improve the morphology of thermoplastic modified epoxies. © 1993 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1993.070480612
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  • 15
    Electronic Resource
    Electronic Resource
    The effect of sudden strain-rate change on the yield behavior of bisphenol-A polycarbonate (1974)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 14 (1974), S. 691-695 
    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: We wish to investigate the path dependence of yield processes in glassy polymers and to understand this dependence, if any, in terms of molecular mechanisms. To this end the effect of sudden strain-rate change on the yield behavior of bisphenol-A polycarbonate has been investigated. In the experiment, a specimen was initially deformed at a constant elongation rate R1; at an elongation Δlc the rate was suddenly changed to another constant elongation rate R2. R1 was either lower or higher than R2. The yield stress subsequent to the rate change was found to be lower than if the entire deformation was at R1. These results can be satisfactorily explained in terms of Robertson's theory of the yielding of glassy polymers if it is assumed that the “bond flexing” in his theory manifests itself in anelastic deformation.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760141006
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  • 16
    Electronic Resource
    Electronic Resource
    Preparation and characterization of maleimide-terminated poly(arylene ether sulfone) oligomers of various molecular weights (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 43 (1991), S. 1849-1858 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    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 new variation in the bismaleimide (BMI) resin family, maleimide-terminated poly(oxy-1,4-phenylene sulfonyl-1,4-phenylene) oligomers, has been synthesized. The preparation of oligomers (n = 1-12) is described in this study. The structure of these oligomers is characterized by FT-IR and NMR spectroscopy. These oligomers are light yellow to light gray powders that can be melted or dissolved in solvents. Their terminating group bismaleimide has relatively high reactivity. Therefore, these BMI resins can be cured at 250°C to form a crosslinked product. Since the backbone chain is poly(arylene ether sulfone), the cured polymers have high Tg's, which increased from 220°C to higher than 340°C as the number of repeating units n of the corresponding oligomers decreases.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1991.070431008
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  • 17
    Electronic Resource
    Electronic Resource
    Curing reaction and product properties of polysulfones terminated with active functional groups (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 43 (1991), S. 1865-1874 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    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 processes of maleimide-terminated polyether sulfone oligomers (Mn from 1100 to 3000) and ethynyl-terminated polysulfone prepolymers (Mn from 2600 to 12000) were investigated by means of DSC. The initial temperature of cure reaction is increased, and the apparent activation energy Ea of cure reaction is decreased as the Mn of the uncured prepolymer increases. On the basis of the Tg changes during the curing process, the kinetics of cure is proposed to be similar to a stepwise reaction, although the curing reaction is believed to proceed via a free radical chain mechanism. In this proposed reaction some initial reaction products with many branches and one remaining active functional group are formed first. The more these products occur, the more likely they can interreact to form a network. During the curing process the mobility of the active end group is restricted by the rigid polysulfone chain. Therefore, the reaction is mainly controlled by the movement of polymer, i.e., by the kinetics of diffusion. Films of these cured polymers were made by casting from solution. Their β relaxation peaks at low temperatures were examined by dielectric and dynamic mechanical measurements. The films made of the prepolymer with Mn 〉 3000 are flexible and foldable.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1991.070431010
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  • 18
    Electronic Resource
    Electronic Resource
    Preface (1987)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 27 (1987), S. 1-1 
    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
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760270102
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  • 19
    Electronic Resource
    Electronic Resource
    Preface (1987)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 27 (1987), S. 109-109 
    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
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760270202
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  • 20
    Electronic Resource
    Electronic Resource
    Evolution of structure and properties of a liquid crystalline epoxy during curing (1997)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 35 (1997), S. 2363-2378 
    Details
    ISSN: 0887-6266
    Keywords: liquid crystalline thermoset ; epoxy ; curing ; structural evolution ; thermal and mechanical properties ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The evolution of structure, and thermal and dynamic mechanical properties of a liquid crystalline epoxy during curing has been studied with differential scanning calorimetry (DSC), polarized optical microscopy, x-ray scattering, and dynamic mechanical analysis. The liquid crystalline epoxy was the diglycidyl ether of 4,4′-dihydroxy-α-methylstilbene (DGEDHMS). Two curing agents were used in this study: a di-functional amine, the aniline adduct of DGEDHMS, and a tetra-functional sulfonamido amine, sulfanilamide. The effects of curing agent, cure time, and cure temperature have been investigated. Isothermal curing of the liquid crystalline epoxy with the di-functional amine and the tetra-functional sulfonamido amine causes an increase in the mesophase stability of the liquid crystalline epoxy resin. The curing also leads to various liquid crystalline textures, depending on the curing agent and cure temperature. These textures coarsen during the isothermal curing. Moreover, curing with both curing agents results in a layered structure with mesogenic units aligned perpendicular to the layer surfaces. The layer thickness decreases with cure temperature for the systems cured with the tetra-functional curing agent. The glass transition temperature of the cured networks rises with increasing cure temperature due to the increased crosslink density. The shear modulus of the cured networks shows a strong temperature dependence. However, it does not change appreciably with cure temperature. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 2363-2378, 1997
    Additional Material: 20 Ill.
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