ISSN:0032-3888    

DOI:10.1002/pen.760270902

出版商:Society of Plastics Engineers    

年代:1987

数据来源: WILEY

摘要:

AbstractIn a thermodynamic model of the glass transition, general but circular relations for the compositional variation of the glass‐transition temperature,Tg, can be derived from the entropy, the volume, and the enthalpy. The circumstances necessary for each of these to reduce to predictive relations are stated. Of these relations, that derived from the entropy should be the most general because of the expected rather wide applicability of the random mixing assumption, with which it is associated. The entropic theory is used to account for several aspects of the compositional variation ofTg, including problems not of solutions per s

ISSN:0032-3888    

DOI:10.1002/pen.760270903

出版商:Society of Plastics Engineers    

年代:1987

数据来源: WILEY

摘要:

AbstractThe synthetic membranes currently used for soil stabilization and road construction are mainly made of polypropylene and of polyesters. They are used separately for each application. The polymer used has an effect on the wettability and, the permeability of the membrane. The polypropylene membranes, for instance, have a zero wettability, whereas it is high for polyester membranes. This paper reports on the mechanical properties and the permeability of mixtures of polypropylene (PP) and poly(ethylene terephthalate) (PET). The elastic modulus of the mixture was at a minimum for a 50/50 mixture. For the other compositions, the moduli gave a positive deviation as compared with the additivity equation results. This is probably due to the fact that pure PET has a fragile behavior at the temperature at which the mechanical tests were run. This 50/50 composition corresponds to the domain where a phase inversion occurs. The permeability to water vapor gave an S‐shape curve that is typical of a “mixture” of immiscible polymers. The diffusion of the water molecules is controlled by the continuous phase. To compatibilize the two homopolymers, a 94/6 copolymer of PP and of polyacrylic acid was added, at various levels, to a 60/40 mixture of PET and PP: This did not affect markedly the elastic modulus. The yield stress increased, however, indicating that we had a better adhesion and that the copolymer seems to have a certain emulsifier effect, increasing the quality of the dispe

ISSN:0032-3888    

DOI:10.1002/pen.760270904

出版商:Society of Plastics Engineers    

年代:1987

数据来源: WILEY

摘要:

AbstractA series of blends was prepared with broad concentration ranges of polycarbonate (PC) and styrene‐acrylonitrile copolymers (SAN) containing 5.5 and 30 weight percent acrylonitrile (AN). These blends were then injection molded, and their properties were measured and correlated with the morphologies of the blends (as determined by transmission electron microscopy). The toughness properties were shown to be discontinuous and very sensitive to composition of the continuous phase in the blends. The dart impact toughness remained high up to 30–40 weight percent SAN and dropped rapidly above this SAN concentration. The notched Izod toughness fell off rapidly at 10 weight percent SAN and greater. The strength and modulus had a more linear dependence on composition. Results of studies of theTgby differential scanning calorimetry (DSC) show the presence of two phases over the entire concentration and a small solubility of each phase in the other. The heat distortion temperature under load (DTUL) of the blends approximated a linear additivity curve for the components. As expected, the blends had much better clarity where the refractive indexes more nearly match (in the case of the 5.5 percent AN copolym

ISSN:0032-3888    

DOI:10.1002/pen.760270905

出版商:Society of Plastics Engineers    

年代:1987

数据来源: WILEY

摘要:

AbstractTo help make a good polymer blend by melt blending, the properties of polycarbonate (PC)/acrylonitrile‐butadiene‐styrene (ABS) systems with various compositions have been investigated. As ABS is blended into PC to form a binary system, Brabender torque is reduced, a phenomenon that results in Improved processability of PC. With increasing ABS content, the mechanical properties of the blends such as tensile strength, modulus, hardness, and shrinkage decrease. However, with the variation of composition, Izod impact strength shows a maximum, while elongation at break exhibits a minimum. These phenomena are discussed with dynamic viscoelasticities and scanning electron microscopic morphological results. The value of ΔTg(TgβPC−TgβABS) is at its smallest when the ratio of PC to ABS is 90:10, However, the value rises with an increase in ABS because the butadiene content of the ABS hinders compatibility in the binary system. At the 90:10 composition, the damping height is optimal. In addition, the dispersed phase of the ABS is most ideal, absorbing the impact force and showing high impact strength. Composition ratios other than 90:10 present high damping as well as undesirable phase separation because of poor adhesion between two phases. As a result, the mechanical properties are

ISSN:0032-3888    

DOI:10.1002/pen.760270906

出版商:Society of Plastics Engineers    

年代:1987

数据来源: WILEY

摘要:

AbstractThe recycling of plastic waste is of particular interest in large urban areas where municipal waste represents a large ecological problem. To achieve their objective (consumer products from plastic waste), formulators of a recycling program have to understand the implications of working with mixtures of different resins. Furthermore, in a multiphase system, the thermomechanical history experienced by the resins during processing represents an important link between operating conditions, resin properties, and final product performance. High‐density polyethylene/low‐density polyethylene (HDPE/LDPE) blends (10, 20, 35, 50, 65, 80, and 90 percent by weight HDPE) were melt blended in an internal mixer. A complete rheological characterization was performed on each blend. The resulting blends were extruded under different processing conditions. The extruded sheets were further characterized to determine their mechanical properties, The experimental results show important differences in the mechanical properties (transverse and longitudinal) of the sheets obtained from the blends. These differences are explained on the basis of the processing conditions (thermomechanical history) and the rheological properties of the molten ble

ISSN:0032-3888    

DOI:10.1002/pen.760270907

出版商:Society of Plastics Engineers    

年代:1987

数据来源: WILEY

摘要:

AbstractThe formation, mechanical properties, thermal characteristics, and density of diffuse shear banded zones of polystyrene, poly(2,6‐dimethyl‐1,4‐phenylene oxide) (PPO), and their miscible blends were studied. A significant increase in density of 0.2 to 0.3 percent was found for the diffuse shear banded zones. Differential scanning calorimetry results revealed a volume recovery process that occurs belowTgfor the diffuse shear banded zones. The post‐yield‐stress drop, anelastic shear strain within the zone, and anelastic tensile strain were all found to decrease with increasing PPO content in an identical manner. The sharp shear band to diffuse shear banded zone transition was related to chain mobility, molecular packing, and free energy as manifested in the post‐yield‐stress drop. The decrease in anelastic shear strain with increasing PPO content for the blends is possibly related to the beta transition and length between

ISSN:0032-3888    

DOI:10.1002/pen.760270908

出版商:Society of Plastics Engineers    

年代:1987

数据来源: WILEY

摘要:

AbstractThe morphology of blends of polycarbonate and nylon 6,6 with a copolyester of 60 mole percent p‐hydroxybenzoic acid/40 mole percent poly(ethylene terephthalate) was characterized under different processing conditions. In particular, single‐screw extrusion, steady simple shear flow, and flow through a capillary were studied to determine what conditions were necessary for the development of a fibrillar morphology of the liquid crystalline polymer (LCP). Results indicate that some extensional flow is required for the coalescence and extension of the particulate LCP phase. The viscosity of the blends was determined both in a cone‐and‐plate geometry of a Rheometrics Mechanical Spectrometer at low shear rates and in the Instron Capillary Rheometer at higher rates. In general, only a small (10 or 30 percent) weight fraction of LCP was required to reduce the viscosity of the thermoplastics to that of the polymeric liquid crystal. An attempt was made to correlate the structure of the blends seen under the scanning electron microscope with the observed rheology. Not all aspects of the morphology were possible to explain in terms of the viscous properties of the

ISSN:0032-3888    

DOI:10.1002/pen.760270909

出版商:Society of Plastics Engineers    

年代:1987

数据来源: WILEY

摘要:

AbstractPolymer‐polymer blends offer a route for enhancement of various properties. When immiscible polymers are blended together (in the presence of a compatibilizer), the blend properties are dependent on the morphology of the phases. Uniform, fine dispersions generally result in “average” properties. Discussed here are blends of polyamides or polyesters with polyolefins, particularly polyethylene, where small amounts (3–20 percent) of the former polymers dispersed as essentially parallel, thin, large laminae produce substantial reduction (3–100 times) of permeability properties in blow‐molded/extruded articles. Physical properties of such blends, their permeability properties, and morphologies ar

ISSN:0032-3888    

DOI:10.1002/pen.760270910

出版商:Society of Plastics Engineers    

年代:1987

数据来源: WILEY

摘要:

AbstractThis paper reports the synthesis of a series of urethanetoughened methacrylate resins and evaluation of the fracture toughness (KIC) of these materials. The incorporation of high‐molecular‐weight polyfunctional urethanes produced resins with the best mechanical properties, important to applications as dental biomateri

ISSN:0032-3888    

DOI:10.1002/pen.760270911

出版商:Society of Plastics Engineers    

年代:1987

数据来源: WILEY