摘要:

AbstractThe transitional behavior of poly(vinylidene fluoride) (PVF2) blends with poly(methyl acrylate) and with poly(ethyl acrylate) was examined by differential thermal analysis and dynamic mechanical testing. Both blend systems were judged to be miscible on the bases of the presence of single, composition dependent glass transitions and of the strong melting point depression of the PVF2component, Blends of poly(isopropyl acrylate) with poly(vinylidene fluoride) were found to be immiscible. These results suggest that miscibility of the acrylate series depends on a specific attractive interaction between the PVF2and oxygen within the acrylate and the effect of this interaction is diminished as the hydrocarbon content of the ester is increased.

ISSN:0032-3888    

DOI:10.1002/pen.760180902

出版商:Society of Plastics Engineers, Inc.    

年代:1978

数据来源: WILEY

摘要:

AbstractBlends of poly(vinylidene fluoride) PVF2, with poly(vinyl acetate), PVAc; with poly(vinyl propionate), PVPr; and with poly(vinyl butyrate), PVBu, were prepared by solution blending. Solutions containing PVF2with either PVPr or PVBu exhibited phase separation, and it was concluded that neither of these polymers are miscible with PVF2. Phase separation did not occur with solutions containing PVF2and PVAc. Dried samples of this blend system were subjected to differential thermal analysis, dynamical mechanical testing, and visual observations of their melts. From these results, it was concluded that PVF2and PVAc are miscible. The detailed results and the structural implications of these observations are discussed.

ISSN:0032-3888    

DOI:10.1002/pen.760180903

出版商:Society of Plastics Engineers, Inc.    

年代:1978

数据来源: WILEY

摘要:

AbstractAn experimental study was carried out to investigate the flow behavior of gas‐charged molten polymers in foam extrusion. For the study, a rectangular slit die with glass windows was constructed to permit visual observations, from the direction perpendicular to flow, of the dynamic behavior of gas bubbles when a gas‐charged molten polymer flows between two parallel planes. Pictures were taken of gas bubbles in the flow channel with the aid of a camera attached to a microscope, and these were later used to determine the position at which gas bubbles start to grow. Using three melt pressure transducers mounted on the short side of the rectangular slot, pressure distributions were measured along the longitudinal centerline of the die. The polymeric materials used were high‐density polyethylene and polystyrene, and the chemical blowing agents used were a proprietary hydrazide which generates nitrogen, and sodium bicarbonate which generates carbon dioxide. It was observed that the gas‐charged molten polymer shows acurvedpressure profile as the melt approaches the die exit, whereas the polymer without a blowing agent shows alinearpressure profile. The visual observations of the bubble growth in the flow channel, together with the pressure measurements, permitted us to determine the bubble inflation pressure, often referred to as the critical pressure for bubble inflation. It was found that the critical pressure decreases with increasing melt extrusion temperature, and increases with increasing blowing agent concentration. It was also found that the bulk viscosity of gas‐charged molten polymers decreases with increasing blowing agent concentration and with increasing melt temperature. A general remark is made concerning the precaution one should take when an Instron rheometer is used for determining the bulk viscosity of gas‐charged molt

ISSN:0032-3888    

DOI:10.1002/pen.760180904

出版商:Society of Plastics Engineers, Inc.    

年代:1978

数据来源: WILEY

摘要:

AbstractAn experimental study was carried out to gain a better understanding of the dynamic behavior of gas bubbles during the structural foam injection molding operation. For the study, a rectangular mold cavity with glass windows on both sides was constructed, which permitted us to record on a movie film the dynamic behavior of gas bubbles in the mold cavity as a molten polymer containing inert gas was injected into it. The mold was designed so that either isothermal or nonisothermal injection molding could be carried out. Materials used were polystyrene, high‐density polyethylene, and polycarbonate. As chemical blowing agents, sodium bicarbonate (which generates carbon dioxide), a proprietary hydrazide and 5‐phenyl tetrazole, both generating nitrogen, were used. Injection pressure, injection melt temperature, and mold temperature were varied to investigate the kinetics of bubble growth (and collapse) during the foam injection molding operation. It was found that the processing variables (e.g., the mold temperature, the injection pressure, the concentration of blowing agent) have a profound influence on the nucleation and growth rates of gas bubbles during mold filling. Some specific observations made from the present study are as follows: an increase in melt temperature, blowing agent concentration, and mold temperature brings about an increase in bubble growth but more non‐uniform cell size and its distribution, whereas an increase in injection pressure (and hence injection speed) brings about a decrease in bubble growth but more uniform cell size and its distribution. Whereas almost all the theoretical studies published in the literature deal with the growth (or collapse) of astationary single sphericalgas bubble underisothermalconditions, in structural foam injection molding the shape of the bubbleis not spherical because the fluid is in motionduring mold filling. Moreover, a temperature gradient exists in the mold cavity and the cooling subsequent to mold filling influences bubble growth significantly. It is suggested that theoretical study be carried out on bubble growth in an imposed shear field undernonisothermalcondi

ISSN:0032-3888    

DOI:10.1002/pen.760180905

出版商:Society of Plastics Engineers, Inc.    

年代:1978

数据来源: WILEY

摘要:

AbstractThe melting or plasticating behavior of seven commercial polymers (high density polyethylene, low density polyethylene, polypropylene, polyoxymethylene copolymer, polystyrene, poly(methyl methacrylate), and polycarbonate (PC) was investigated using an experimental apparatus specifically designed to measure the melting rate and the viscous shear stress of a solid polymer on a steel surface under precisely controlled conditions of temperature, velocity, pressure and sample width comparable to actual processing. The melting rate (per unit polymer solid/metal contact area) was found to increase with increasing temperature for all polymers except PC, to decrease with increasing sample width and to increase less than proportionally to velocity. Pressure increased the melting rate somewhat for most of the polymers. The viscous shear stress decreased with increasing temperature for all polymers except PC, decreased with increasing sample width and increased with increasing velocity. Pressure generally increased the viscous shear stress. PC showed an unusual behavior with a maximum in the melting rate near 4200°F(215.5°C) and also a maximum in the viscous shear stress near 445°F (229.4°C). The present melting model could be examined unequivocally for the first time using our experimental results. Comparison of our experimental results with the predictions of the present melting model clearly indicates the inadequacy of the present melting model, Our experimental results will provide a basis for rational development of a reliable melting mo

ISSN:0032-3888    

DOI:10.1002/pen.760180906

出版商:Society of Plastics Engineers, Inc.    

年代:1978

数据来源: WILEY

摘要:

AbstractPyrolysis of polymer wastes appears to be a suitable means of dealing with an increasingly important environmental problem. To provide background on the pyrolytic behavior of wastes, model mixtures of polyethylene and polystyrene have been pyrolyzed in various gas phases including nitrogen and carbon monoxide, at atmospheric and at reduced pressures and at temperatures from about 300–900°C. When the pyrolyzing temperature is attained by gradual heating, and when pyrolysis occurs at pressures in excess of about 200 torr, the process occurs as if each component were present alone—that is, no evidence for component interaction was noted. In these cases, the known mechanisms for pyrolysis of the pure polymers can be applied to the behavior of mixtures. Complicating effects due to interactions between the starting polymers, or among the pyrolysis products, were observed in low pressure pyrolysis (≲20 torr); further, it was shown that the balance of pyrolysis products depends on rates of attaining the pyrolyzing temperature, more rapid rates favoring the production of carbon‐rich solid residues of possible use as carbon blacks. More detailed understanding of pyrolytic processes in polymer mixtures is needed to permit selection of conditions producing the optimum balance of useful

ISSN:0032-3888    

DOI:10.1002/pen.760180907

出版商:Society of Plastics Engineers, Inc.    

年代:1978

数据来源: WILEY

摘要:

AbstractThe analysis of molding operations for thermosetting polymers requires knowledge of the rheology and reaction rates of the materials. The purpose of this research was to measure kinetic and rheological data on diallyl phthalate resins and to integrate these results into models describing the flow behavior. The chemical kinetics of the curing reactions were derived from calorimetric measurements taken with a differential scanning calorimeter. The rheological data were measured with a mechanical spectrometer equipped with eccentric rotating discs. A model based on the theory of ideal rubber elasticity was used to correlate the elastic storage modulus with reaction time and temperature. For the region below the gel point, the dynamic viscosity exhibited a power law dependence on angular frequency and an Arrhenius dependence on temperature.

ISSN:0032-3888    

DOI:10.1002/pen.760180908

出版商:Society of Plastics Engineers, Inc.    

年代:1978

数据来源: WILEY

摘要:

AbstractExperiments are performed on the dynamics of formation of a liquid coating picked up by a cylindrical roll rotating partially submerged in a free bath. Data on coating thickness for Newtonian fluids are found to correlate according toT=H(ρg/μU)1/2= 0.56 for fluids whose viscosities range from 0.11 to 33 poise. Data for strongly non‐Newtonian and Viscoelastic fluids (polyacrylamide solutions) can be forced to fit this correlation by defining an “equivalent coating viscosity.” It is clear that this defines a pseudo viscosity, because the “equivalent coating viscosity” is observed to increase with increasing roll speed. This suggests that strongly Viscoelastic fluids respond to the rapid deformation suddenly imposed in the dynamic meniscus near the pickup point in a distinctly elastic manner that alters the flow through t

ISSN:0032-3888    

DOI:10.1002/pen.760180909

出版商:Society of Plastics Engineers, Inc.    

年代:1978

数据来源: WILEY

摘要:

AbstractConsideration of the basic equation for mixing in plane strain laminar flow shows that mixing can proceed much more rapidly than has been commonly accepted. While linear rates of mixing have been predicted previously, exponential rates of mixing are possible. An upper bound for, the rate of mixing in plane strain laminar flow is shown to be an exponential. The geometry of the flow which produces this most rapid mixing is shown to be plane strain extensional flow, sometimes called pure shear flow, with all interfaces aligned normally to the smallest principle axis of the deformation.

ISSN:0032-3888    

DOI:10.1002/pen.760180910

出版商:Society of Plastics Engineers, Inc.    

年代:1978

数据来源: WILEY

ISSN:0032-3888    

DOI:10.1002/pen.760180901

出版商:Society of Plastics Engineers, Inc.    

年代:1978

数据来源: WILEY