摘要:

AbstractFor batchwise radical chain solution multicomponent copolymerization, the minimum end time problem for the predetermined monomer conversion and number average molecular weight has been studied by considering the initiator concentration (or feed rate) and temperature as the two control variables. Applying the maximum principle and “unit segment treatment” (by which the co‐polymerization can be treated as homo‐polymerization in the kinetic analysis), it is found that for initiator addition processes the optimal initiator addition policy is to make the rate of initiation constant for the optimal temperature variation case, and the initiator concentration constant for the isothermal case as in homo‐polymerization. For single charge of initiator processes, the optimal initial initiator concentration is such that it should be maintained at the lowest possible value (by which the polymerization is strongly dead‐end) for the optimal temperature variation case without chain transfer steps, and at some optimal value (by which the polymerization is near dead‐end) for the best is

ISSN:0032-3888    

DOI:10.1002/pen.760251602

出版商:Society of Plastics Engineers, Inc.    

年代:1985

数据来源: WILEY

摘要:

AbstractA systematic study of wall effects on the shear viscosity of short glass fiber‐filled polypropylene and polystyrene is presented. The dependence of these effects on capillary radius, shear rate, temperature, and polymer matrix is examined. The “true” viscosity curves of these materials (free from wall effects) can be obtained by an extrapolation procedure. Breakage of glass fibers in the high shear‐rate processes of extrusion and injection molding lead to an appreciable reduction of the viscosity of these materials and is probably the more important effect to take into account in these pr

ISSN:0032-3888    

DOI:10.1002/pen.760251603

出版商:Society of Plastics Engineers, Inc.    

年代:1985

数据来源: WILEY

摘要:

AbstractMold filling of a rectangular cavity of three different thick nesses fed from a reservoir is studied for unfilled and glass fiber‐filled polypropylene and polystyrene. The shapes of flow fronts studied by short‐shots are affected predominantly by the thickness of the cavity with other parameters playing a less important role. Pressure drop versus volumetric flow rate inside the thinnest cavity is studied experimentally and predictions are made from a computer simulation of mold filling. The orientation of fibers in the cavity is examined using a reflect‐type microscope and the orientation is found to depend on cavity thickness, melt temperature, fiber content, and to a lesser extent, on volumetric flow rate. In the thinnest cavity, where the flow is quasi‐unidirectional, the fibers remain in the plane of flow oriented either along the flow direction or perpendicular to it, except in the region near the flow front, where they follow a “fountain” fl

ISSN:0032-3888    

DOI:10.1002/pen.760251604

出版商:Society of Plastics Engineers, Inc.    

年代:1985

数据来源: WILEY

摘要:

AbstractThe accurate but complex McAllister model for the melt viscosities (η) of binary polymer blends has been greatly simplified by dropping the terms involving only mole fraction and molecular weight, by switching from mole fraction to mass fraction, and by making the model explicit in dynamic, rather than kinematic, viscosity. The simpler Lecyar model was tested side‐by‐side with the McAllister in five binary systems and at seven levels of shear rate from 5 to 500 s−1in each system. For the 35 pairs of curves fitted, the rms standard error of estimate was 0.0945 (In η), for the Lecyar modelversus0.0911 for the McAllister; the difference corresponds to only 0.4 percent additional error in the blend viscosity. Comparison of results in two systems, reported by Carley and Crossan (12) with those of other workers, indicate that the differences among what appear to be comparable, self‐consistent data sets are much greater than the within‐set errors of rheometric measurement and mo

ISSN:0032-3888    

DOI:10.1002/pen.760251605

出版商:Society of Plastics Engineers, Inc.    

年代:1985

数据来源: WILEY

摘要:

AbstractThis review is mainly concerned with the conformational changes that depend on the dielectric constants for solvents for chlorinated polybutadienes (Cl‐PBD) and their model compounds. The conformational equilibria of the rotational isomers of both meso and racemie 2,3‐dichlorobutanes and 3,4‐dichlorohexanes as the model compounds are discussed by analyzing infrared and NMR spectra. The solvent effect on the conformational parameter in Cl‐PBD is explained by the variation in the conformation of the chlorinated part having polar C‐Cl bonds. The matrix method is also described to calculate the temperature and solvent dependences of conformer po

ISSN:0032-3888    

DOI:10.1002/pen.760251606

出版商:Society of Plastics Engineers, Inc.    

年代:1985

数据来源: WILEY

摘要:

AbstractThis paper presents the results of a testing program carried out on the fracture properties of poly(methyl methacrylate) (PMMA). The objective of the program was to determine the validity of using standard impact test methods to obtain fracture data, as opposed to the more expensive fracture toughness tests. It was found that impact test results may be used to evaluate fracture properties for PMMA with correlation being obtained with fracture toughness test data.

ISSN:0032-3888    

DOI:10.1002/pen.760251607

出版商:Society of Plastics Engineers, Inc.    

年代:1985

数据来源: WILEY

摘要:

AbstractIn order to achieve a better understanding of polymer blending processes some experimental work has been carried out on the deformation and break‐up behavior of liquid droplets in simple shearing matrices. For Newtonian systems good agreement was obtained with existing theories. For non‐Newtonian systems trends were established regarding the influence of fluid elasticity on droplet deformation and break

ISSN:0032-3888    

DOI:10.1002/pen.760251608

出版商:Society of Plastics Engineers, Inc.    

年代:1985

数据来源: WILEY

摘要:

AbstractBlends of poly(2,6‐dimethyl‐1,4‐phenylene oxide) (PMMPO) and poly(4‐methylstyrene) (P4MS) were found to be compatible from a variety of experimental methods including calorimetric, density, and mechanical property measurements. Blend property behavior was similar to that widely reported for PMMPO/polystyrene (PS) blends. For each blend composition studied, a single glass transition temperature (Tg) was detected by differential scanning calorimetry. The compositional dependence of blendTgwas equally well represented by the empirical inverse rule of mixtures or by the Couchman thermodynamic expression. Density measurements of molded films suggested a mild excess volume of mixing that was slightly smaller than that observed for blends of PMMPO and PS. As in the case for PMMPO/PS, densification in the solid state may be associated with the observed mechanical property behavior of the PMMPO/P4MS blends. Initial modulus at each blend composition was larger than would be predicted by a simple weighted average of component polymer values. Tensile deformation changed from a ductile to a brittle mode of failure with increasing P4MS composition. The yield stress for ductile compositions and ultimate stress of brittle samples were both higher than found for the corresponding unblended polymers and higher than would be predicted from a simple additive relationship of weighted component properties. Blend impact strength determined by small strain rate tensile tests rapidly decreased to low levels with increasing P4MS composition. This drop in impact strength became more composition sensitive at higher loading rates during multiaxial deformation in an instrumented dart impact

ISSN:0032-3888    

DOI:10.1002/pen.760251609

出版商:Society of Plastics Engineers, Inc.    

年代:1985

数据来源: WILEY

ISSN:0032-3888    

DOI:10.1002/pen.760251601

出版商:Society of Plastics Engineers, Inc.    

年代:1985

数据来源: WILEY