ISSN:0730-6679    

DOI:10.1002/adv.1991.060110101

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY

摘要:

AbstractA common technique for the manufacture of polymer alloys is melt blending of polymers with specific chemical interactions. For instance, an amido ester crosslink forms when oxazoline‐grafted PS is mixed with acid‐grafted PE. The crosslink builds melt viscosity and stabilizes product morphology. Reaction control is critical since overreacted alloys from gels and underreacted alloys have gross composition gradients and/or tend to phase coalesce so that product properties are variable. Polymer reactions in plasticating compounders are particularly difficult control problems since several unit operations involving plastication, heat exchange, mixing, and separating of by‐products must be sequenced properly to control a reaction. Reactive polystyrene (OPS) and reactive polyethylene (APE) with oxazoline and carboxylic acid functionality, respectively, were melt blended in a ZSK compounding extruder under a variety of conditions. The extent of crosslink was monitored by the strong shear viscosity increase of the reacted product, the infrared absorption by the crosslink, and reactant depletion in the melt. The phase morphology was characterized by optical phase contrast microscopy. A response surface of product shear viscosity vs. the primary operational parameters of extrusion rate and extruder RPM is interpreted in terms of characteristic reaction time and development of reactive interfaces during the mixing process. Response surfaces result from storing coordinates and responses while exercising a new feedback loop control s

ISSN:0730-6679    

DOI:10.1002/adv.1991.060110102

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY

摘要:

AbstractVisual studies have been performed on the partially filled, nonintermeshing twin‐screw extruder (NITSE) to determine its distributive mixing abilities. Four parameters were studied: percent screw stagger, percent channel fill, screw speed, and fluid viscosity. It was found that screw speed and viscosity had no statistically significant effect on mixing, while percent channel fill and percent screw stagger were factors affecting mixing that were intimately related by the type of screw‐to‐screw fluid transfer. The two types of transfer were fluid‐to‐fluid, which occurred when the percent fill was greater than the percent stagger, and deposition, which occurred when the percent fill was less than the percen

ISSN:0730-6679    

DOI:10.1002/adv.1991.060110103

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY

摘要:

AbstractThe first quantitative description of melting in single‐screw extruders was given by Tadmor around 1965. A simple analytical theory was developed for Newtonian fluids assuming the fluid viscosity to be unaffected by changes in temperature. Also, an approximate analytical theory was developed for a power‐law fluid assuming the power‐law constants to be independent of temperature and viscous dissipation to be negligible. Later workers extended the theory; however, most of these extensions did not allow closed‐form analytical solutions, thus requiring numerical techniques to obtain solutions. One of the most crucial assumptions in the analytical melting theory is the assumption that the viscosity of the polymer melt in the melt film is not affected by temperature differences in the melt film. This assumption has been eliminated in the improved melting theory by deriving and exact solution of the temperature and velocity profile in pure drag flow of a temperature‐dependent power‐law fluid between two parallel plates. It will be shown that the inclusion of the temperature dependence of the viscosity dramatically affects the predictions of the melting rate. It will further be shown how the new theory can be used to predict the optimum barrel temperature

ISSN:0730-6679    

DOI:10.1002/adv.1991.060110104

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY

摘要:

AbstractA realistic criterion was introduced in the 3D principal stress space for describing failure of transversely isotropic bodies taking also into account the strength differential effect. This criterion is represented by an elliptic paraboloid failure surface (EPFS). The criterion stipulates that in the compression–compression–compression octant these materials may sustain very high loadings. To remedy this ambiguous definition of failure in this zone, an improved version of the EPFS was also introduced as a complement of the EPFS criterion. Based on the same principles as the EPFS, a symmetric ellipsoid failure surface is defined whose symmetry axis is parallel to the hydrostatic axis, which is also passing though the three pairs of failure strengths in tension and compression along each of the principal stress axes. Both criteria are completely defined by stipulating that their symmetry axes are parallel to the hydrostatic axis and that the fourth rank tensors H defining failure should have a zero eigenvalue associated with the spherical tensor 1. Extensive experimental evidence with different orthotropic materials has shown that their failure results corroborate both criteria, depending on the form of their struct

ISSN:0730-6679    

DOI:10.1002/adv.1991.060110105

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY

摘要:

AbstractThe thermal and crystallization behavior of polyphenylene sulfide (PPS) in the context of its structure development in solid‐state processing is reported. The solid‐state processing of polymers involves cold compaction of the powder, followed by sintering. Since this process comprises of heat treatment at high temperatures for extended periods, the structure of PPS would be expected to be affected. An attempt has been made to elucidate the effect of compaction and sintering process parameters on the physical and chemical structures of the polymer. The changes in the structure of the polymer were monitored by characterizing its melting and crystallization behavior. It was observed that compaction resulted in changes only in the physical structure, leading to destruction of the smaller/less stable crystallities. The thermal treatment at high temperatures led not only to physical changes involving crystal growth and perfection but also to chemical changes in the structure, resulting in modification of crystallization behavior. The extent of change was found to be different for PPS in the powder form and in the pellet form, which is explained on the basis of the restricted diffusion of air in pellet form as compared to the powder. Such changes observed in the samples were also dependent on the type of sintering medium. The sintering in presence of nitrogen did not show significant changes in the crystallization or melting behavior. Thus, the structure development in solid‐state processing of PPS was influenced by the sintering time, temperature, and sintering medium, leading to physical and/or chemical ch

ISSN:0730-6679    

DOI:10.1002/adv.1991.060110106

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY

摘要:

AbstractThe injection‐molding process for high‐performance ceramics is rapidly spreading into various kinds of industries, particularly the automobile industry. In this study, we provide an outline of the ceramics injection‐molding process, its characteristics, the difference between ceramics compounds and plastics, and examples of applica

ISSN:0730-6679    

DOI:10.1002/adv.1991.060110107

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY

ISSN:0730-6679    

DOI:10.1002/adv.1991.060110108

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY

ISSN:0730-6679    

DOI:10.1002/adv.1991.060110109

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY