Thermotropic polyester carbonates. II. Polyester carbonates as high performance fibers

The fiber spinning and heat treatments of spun fibers from thermotropic polyester carbonates are described. Thermotropic polyester carbonates derived from t-butylhydroquinone, methylhy-droquinone, diphenyl terephthalate, and diphenyl carbonate in the molar ratios of 50 : 50 : 55 : 45; 50 : 50 : 57.5 : 42.5; can be spun successfully, and after proper heat treatment, yield fibers with tenacity as high as 20 g/denier. Normally the best spinning temperature is 10–20°C above melting.     

Thermotropic polyester amide-carbon fiber composites

Liquid crystal polymers (LCP) have been developed for the first time as a thermoplastic matrix for high-performance composites. A successful melt impregnation method has been developed that results in the production of continuous carbon fiber (CF)-reinforced LCP prepreg tape. Subsequent layup and molding of prepreg into laminates has yielded composites of good quality. Tensile and flexural properties of LCP-CF composites are comparable to those of epoxy-CF composites. LCP-CF composites have better impact resistance than the latter, although epoxy-CF composites possess superior compression and shear strength. LCP-CF composites have good property retention until 200°F (67% of room temperature value). Above 200°F, mechanical properties are found to decrease significantly. Experimental results indicate that the poor compression and shear strength may be due to the poor interfacial adhesion between the matrix and carbon fiber.     

PCT高性能聚酯工程塑料

综述了以环己烷二甲醇与对苯二甲酸二甲酯合成PCT(聚对苯二甲酸环己烷二甲醇酯)树脂及其本体树脂PCT的加工技术(包括GFRPCT、共混等),对PCT树脂的物理、机械性能及其典型应用也作了介绍。     

Thermotropic polyester: The influence of the spacer on physical properties. II

The thermal transitions of liquid crystalline polyesters have been studied by differential scanning calorimetry and thermooptical microscopy. The physical properties of these thermotropic polyesters, particularly the glass transition and the crystallization temperatures have been investigated. The influence of the spacer type on the transitions has been considered. A glass transition at 64°C was observed of the polyester with oxyethylenic group as flexible spacer while a glass transition could not be observed of the polyester with methylenic groups.     

热塑性聚酯工程塑料的进展

综述了世界上几种热塑性聚酯的生产发展及应用进展，指出聚酯工业的4个主要趋势；生产能力逐渐集中，亚洲生产能力增大；欧美撤出聚酯纤维领域和非纤聚酯比例上升，在应用方面，热塑性聚酯多用于制造片（带）材，中空包装容器，电子、家用电器、汽车、精密仪器部件、薄膜及纤维等领域。     

生物降解聚酯开发和生产进展

评述了国内外各种生物降解聚酯塑料(PBS、PHA等)的开发和生产进展.     

Relations between structure and properties in bisphenol A polyester carbonates

A range of hydroxy-terminated polybisphenol A terephthalate and isophthalate blocks have been prepared with molecular weights 800–5000, which were then coupled with phosgene to give alternating polyester copolycarbonates. These materials have been characterized by their physical, thermal and mechanical properties. The thermal properties have been investigated using differential scanning calorimetry and the glass transition temperatures, specific heats and Δcps′ (at the T_g) values obtained. A relationship appears to exist between Δcp and the reciprocal molecular weight of the polyester blocks, and the molar ratio of ‘ester’ to carbonate of the copolycarbonates. A maximum in the glass transition temperature has also been observed in the copolycarbonates, corresponding to a certain ‘ester’: CO₃ ratio. Tensile mechanical analyses have been performed on cast or moulded films of the copolycarbonates. The terephthalates can give films which extend uniformly but the isophthalates always neck.     

Thermotropic polyester: the influence of the spacer on the physical properties

Thermotropic polyesters prepared from series of 4,4-dihydroxy-,w-diphenoxy alkanes and 4,4-dichloroformyl-,w-diphenoxy alkanes are well known. The substitution of a methylenic spacer by an oxyethylenic spacer in the main chain of these polyesters drastically modifies their physical properties, particularly the mesogenic transition temperatures, as can be observed by DSC and thermooptical analysis. The thermal stability and the polymer solubility in common organic solvents of these polymers did not show a significant change. The physical properties of the two thermotropic polyesters prepared in diphenyl ether were evaluated.     

Experimental determination of ultrasonic wave velocities in plastics as functions of temperature. III. Rigid epoxy foam

The velocity and attenuation of longitudinal bulk waves in a solid epoxy foam were measured by an acoustic pulse technique in the frequency range of 0.667–4.0 Mc./sec. and in the temperature range from ambient to 150°C. The measurements are reported with the density of the solid epoxy and with aluminum impurity loading as parameters. Over the indicated temperature and frequency ranges, complete attenuation and velocity measurements are reported for one foam corresponding to a density of 0.325 g./cc. In the density range of 0.088–0.325 g./cc. for the unloaded foams, attenuation is reported at room temperature. It is observed that the longitudinal velocities for all the densities decrease with temperature by about 40% in a span of 100°C. and that an approximately linear relation exists with temperature. The velocities in the foams loaded with small percentages of aluminum and heat-treated at 250°C. exhibit temperature behavior which is dependent upon the combined effects of loading, density change, and epoxy properties. For the loaded foam with the highest density (1.068 g./cc.), velocity is reported to a temperature of about 250°C. The velocities of all the various density samples with the exception of the loaded foams exhibit inflections at a temperature of about 110°C. The attenuation–temperature measurements on the 0.325 g./cc. sample show similar behavior at this temperature except that the effect is much more pronounced than the velocity inflection, hence a better indication of the transition. The precision of the measurement is about 2% for the relative longitudinal velocities and about 20% for the attenuation.     

Flammability of plastics: III. Reactions between antimony trioxide and organic halogenated flame retardants with reference to their performance in a crosslinked polyester resin

A number of halogenated flame retardants have been heated alone and with antimony trioxide at temperatures between 300 and 500°. Isothermal weight losses over various time periods have been followed. Quantitative analyses of reaction products from heating together both Cereclor 70/Sb₂O₃ and also PVC/Sb₂O₃ have shown antimony trichloride to be the main reaction product in each case.     

Photodegradable vinyl plastics. III. Comparison of ultraviolet light and sunlight exposure

Polystyrene (PS), polypropylene (PP), and polyethylene (PE) films, blended with additives to enhance photodegradability, were irradiated with UV light and sunlight. In almost every case, photodegradation was greater with outdoor exposure than under laboratory conditions. Explanations for the differences in degradation obtained by the two methods of irradiation are discussed. Based on IR measurements and molecular weight determinations, photo-oxidative changes that occur in PS induced by UV light appear similar to those induced by sunlight. In addition to the additives previously reported, several new classes of photoinitiators were evaluated. These include selected halocarbonyl compounds, haloalkyl sulfur compounds, and halogen compounds containing certain electron-withdrawing groups. The performance of the additives in vinyl polymer blends is discussed.     

CO2矿物碳酸化隔离实验初探

引言 煤炭对于世界能源消费特别是对于我国这样一个以煤炭资源为主的发展中国家具有重要意义.     

Engineering plastics from lignin. III. Structure property relationships in solution cast polyurethane films

Lignin-based polyurethane films were synthesized by solution casting from hydroxypropyl lignin derivatives and either an aliphatic or an aromatic isocyanate. Two lignins, kraft and steam explosion lignin, and two diisocyanates, hexamethylene diisocyanate (HDI) and tolylene diisocyanate (TDI), were chosen for the study. It was found necessary to use stoichiometric excess diisocyanate in the synthesis of the thermosetting polyurethanes. This part of the series addresses the effect of synthesis variables on film properties. The study examines the effect of lignin type, of diisocyanate type, and of composition in terms of NCO to OH stoichiometry on thermal and mechanical properties. Stoichiometric NCO-excess was found to cause a more significant increase in the glass transition temperature of TDI-based films than of films made with HDI. The films swelled less with increasing NCO/OH ratio. Use of aliphatic diisocyanate (HDI) resulted in films with lower moduli as compared to aromatic diisocyanate (TDI). Kraft-lignin-based polyurethanes had slightly inferior strength characteristics (Young's modulus and tensile strength) in comparison with those derived from steam explosion lignin. Variation in the NCO/OH stoichiometry had no noticeable effect on modulus or tensile strength, but did significantly influence glass transition temperature, swelling, and strain at break. It is observed that the properties of these thermosetting polyurethanes are very sensitive to their composition. The study illustrates that materials of satisfactory performance characteristics can be engineered by proper selection of synthesis variables and modification of network architecture.     

Grafting onto polyester fibers. III. Electrokinetic properties of acrylic acid and acrylonitrile-grafted polyester fibers in the presence of cationic dyes

The electrokinetic properties such as zeta potential, surface charge density, and surface conductivity of polyester fibers grafted with acrylic acid and acrylonitrile were measured when cationic dye solutions were streamed through. The presence of the cationic dyes on the surface of the fibers and their specific adsorption at the carboxylic groups in the acrylic acid graft copolymer produce lowering of zeta potential. The decrease in surface charge density as the percent graft increases is due to the decrease in surface area of the fibers due to the adsorption of the cationic dyes. The same trend is observed with acrylonitrile-grafted fibers. The surface conductivity of the acrylonitrile-grafted polyester fibers increases with increase in dye concentration of the streaming solution. The results for the 27.4% grafted sample differed from those of the 7.32% and 12.1% grafts, which is indicative of the formation of a three-dimensional network causing change in both the physical structure as well as the chemical nature of the surface of the substrate.     

Rheology of unsaturated polyester resins. III. Effects of filler and low-profile additive on the thickening behavior of unsaturated polyester resin

An investigation was made of the rheological behavior of unsaturated polyester resin during thickening in the presence of filler or low-profile additive alone and, also, in the presence of both filler and low-profile additive. For the study, two different types of filler (CaCO₃ and clay) and two different types of low-profile additive (PMMA and PVAc) were evaluated. Compared to the resin/thickener system, the resin/filler/thickener system exhibits shear-thinning behavior as thickening progresses, and gives rise to smaller normal stress effects. On the other hand, the resin/low-profile additive/thickener system exhibits two distinct Newtonian regimes in the viscosity-shear stress curves and gives rise to larger normal stress effects. The viscosity behavior of the resin/filler/low-profile additive/thickener system was found to be very similar to that of the resin/low-profile additive/thickener system. In all cases, when the first normal stress difference was plotted against the shear stress, a correlation was obtained which was independent of thickening period. This behavior was exactly the same as for thickening polyester resin alone, as discussed in Part II of this series.     

Experimental determination of ultrasonic wave velocities in plastics as functions of temperature. IV. Shear velocities in common plastics

The temperature dependence of acoustic shear velocities are reported for Poly-Penco nylon, type G Plexiglass [poly(methyl methacrylate)], TFE Teflon (tetrafluoroethylene), low- and high-density polyethylene, Lexan (polycarbonate), and Delrin Acetal (nylon). Most of the data were obtained at a frequency of 1 Mc./sec. over the temperature range of 25–100°C. In addition, previously unreported longitudinal velocities to ～125°C. are reported for Lexan and Delrin Acetal.     

电子注塑V.S液压注塑

在光盘复制行业中,许多未曾使用电动注塑机的复制厂正在考虑——选购注塑机是液压型还是电动型?而他们不会忘记注塑机设计中最重要的是螺杆性能,其它的技术问题都列为其次。举例来说如果注射单元不能提供优良的熔融质量,那么即使电动注塑机的夹模单元的精度再高也就失去意义。 注塑机的选购者应该首先考虑熔融性能。意思就是在塑料供应商所规定的温度下,塑化材料应具有均一的熔融特性,否则不一致的熔融特性