摘要:

AbstractA similarity solution is given to a very viscous Newtonian fluidflowing in a channel which is suddenly heated or cooled. The viscosity is assumed purely an exponential function of temperature and heat generation is very large. The asymtoptic approximation is that the downstream viscosity at the channel wall differs by an order of magnitude from that in the upstream flow. This solution can be used to check results of numerical simulation in the injection of either a thermoplastic or a thermoset resin into a cooled or heated mold, respectively.

ISSN:0730-6679    

DOI:10.1002/adv.1988.060080101

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

年代:1988

数据来源: WILEY

摘要:

AbstractThe effect of convection on the melting rate of granular polymeric solids pushed against a hot moving surface was analyzed by including in the energy equation the convection term to compute the melting film thickness. The results of this analysis indicate that the melting film thickness is reduced by the effect of convection, providing a theoretical basis for Tadmor's suggestion to reduce melting film thickness to account for the effect of convection in calculating the melting rate.

ISSN:0730-6679    

DOI:10.1002/adv.1988.060080102

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

年代:1988

数据来源: WILEY

摘要:

AbstractThe effect of density compressibility of granular polymeric solids on the pressure development inside the feed zone of a single screw extruder was calculated. Results indicate that, for a given flow rate, density compressibility enhances pressure rise inside the extruder, remedying the under estimation of previous theory. A substantial rise in pressure buildup may result for compressibility above a certain level. This may explain observed surging during the processing of low bulk density materials.

ISSN:0730-6679    

DOI:10.1002/adv.1988.060080103

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

年代:1988

数据来源: WILEY

摘要:

AbstractThe production of automotive exterior body panels in the PUR–RRIM process is a comparatively new technology that provides a great potential for further improvements and makes it possible to produce plastic components for the automotive industry that, at relatively thin wall thicknesses, meet maximum requirements in regard topart geometrydimensional stabilitythe high industrial standards valid in the automotive industrysurface quality (avoidance of sink marks, pores, etc.)durable fasteningFor a better acceptance of RRIM moldings, cost reductions in the production process are necessary which, in turn, require noticeable progress in the material and process development. Due to the improvements made in the field of both raw materials and production units, the PUR–RRIM process has, in the last few years, become interesting also for high‐volume production. A handicap in this connection is that the development of the RRIM process is, to a large extent, based on the practical experience of a few experts. For its use in high‐volume production it is, however, inevitable to have at hand through scientific data on material, design, process and resulting correlations. It is the objective of the Institute for Polymer Testing and Polymer Science in Stuttgart to help establish these data and, through close contacts to the industry, make them usable in p

ISSN:0730-6679    

DOI:10.1002/adv.1988.060080104

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

年代:1988

数据来源: WILEY

摘要:

AbstractA critical review of research on the development of crystallinity, orientation, and haze in tubular film is presented. We examine the basic methods of characterization of polymer films and interpretation of experimental techniques. Most studies in the literature relate to polyethylene, polystyrene, and polypropylene tubular film. Polymer chain and crystallographic axis orientation have been studied using X‐ray diffraction and birefringence. We critically discuss the representation of such data using biaxial orientation factors. The data appears correlatable in terms of expressing orientation as a function of applied stresses at solidification. It appears that film haze is predominantly caused by surface roughness. This is largely associated with the crystallization of the melt on the process lin

ISSN:0730-6679    

DOI:10.1002/adv.1988.060080105

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

年代:1988

数据来源: WILEY

摘要:

AbstractFine clusters of inorganic compounds (all lowtemperature superconductors) were mixed thoroughly with polymerizing epoxy or urethane monomers. The resulting composites were cured. These polymer composites were formulated at room temperature and pressure. The electrical resistivity of the synthesized composites were measured at room temperature and pressure. Further resistivity measurements were carried out at room temperaturehigh pressure and room pressure–liquid nitrogen temperature. Significant drops in resistivity were found for composites measured at high pressure and liquid nitrogen temperature. Composites in both epoxy and urethane polymers when subjected to pressures of up to 2000 psi had drops in resistivity of up to 6 orders magnitude. Also, composites in urethane when subjected to liquid nitrogen temperature had drops in resistivity of 6 orders in magnitude. In contrast, composites made up in two types of epoxy polymer when subjected to liquid nitrogen temperature had drops of only up to eightfol

ISSN:0730-6679    

DOI:10.1002/adv.1988.060080106

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

年代:1988

数据来源: WILEY

摘要:

AbstractWe have developed instrumentation using an internal‐bubble pressure transducer with a data acquisition system to sense LLDPE bubble stability on a commercial blown‐film line. Real‐time bubble instability was also recorded using a video camera at a speed of 30 frames/s. The pressure signal was analyzed using a fast‐Fourier‐transform (FFT) computer program to determine the frequency of bubble oscillation. Since bubble instability often consists of large‐scale oscillation and bubble flutter, and both motions affect gauge and layflat uniformity, the pressure signal was decomposed to determine the frequency of each oscillation mode. To obtain a stable bubble, the amplitudes of both oscillation modes must be reduced to a minimum. Under a single mode oscillation, the period of bubble‐diameter variation analyzed using videotape matches that of the pressure trace. The initial results indicated that the trace of the pressure can provide a warning to the stability of a blown

ISSN:0730-6679    

DOI:10.1002/adv.1988.060080107

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

年代:1988

数据来源: WILEY

ISSN:0730-6679    

DOI:10.1002/adv.1988.060080108

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

年代:1988

数据来源: WILEY

ISSN:0730-6679    

DOI:10.1002/adv.1988.060080109

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

年代:1988

数据来源: WILEY

ISSN:0730-6679    

DOI:10.1002/adv.1988.060080110

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

年代:1988

数据来源: WILEY