ISSN:0032-3888    

DOI:10.1002/pen.760030102

出版商:Society of Plastics Engineers, Inc.    

年代:1963

数据来源: WILEY

ISSN:0032-3888    

DOI:10.1002/pen.760030103

出版商:Society of Plastics Engineers, Inc.    

年代:1963

数据来源: WILEY

摘要:

AbstractThe movement of coloured markers (polydimethyl siloxane and low density polythene) placed near the die entry before extrusion or injected through the side of the die during extrusion has been measured both above and below the onset of instability. During stable flow the observed velocity distributions are similar to those predicted by assuming that polymer at the die wall is stationary, but when melt fracture occurs there is movement at the wall. The possibility of a stick‐slip mechanism being responsible for unstable flow is examined and evidence in support of this hypothesis is presented. Available evidence suggests that for a given molecular weight, the critical shear stress increases with the polarity of the polymer, and the material of which the die is made has been found to affect the instabilit

ISSN:0032-3888    

DOI:10.1002/pen.760030104

出版商:Society of Plastics Engineers, Inc.    

年代:1963

数据来源: WILEY

摘要:

AbstractThis study summarizes the flow behavior of concentrated and melt systems of linear amorphous polymer. For low molecular weight polymer, viscosity increases regularly with a lower power dependence on molecular weight. This dependence decreases towards first power with increasing temperature but is independent of shear, with viscosities being constant up to the highest attainable steady state stresses, about 106dynes/cm2. At a higher molecular weight, 2,000–40,000, depending on polymer type, the viscosity dependence on molecular weight changes abruptly to a high power which is generally about 3.4. Above the transition, this high power function is independent of temperature but depends markedly on shear. Non‐Newtonian flow sets in abruptly and predictably above the transitional molecular wei

ISSN:0032-3888    

DOI:10.1002/pen.760030105

出版商:Society of Plastics Engineers, Inc.    

年代:1963

数据来源: WILEY

摘要:

AbstractAttempts to operate plastic processing equipment at higher production rates is often accompanied by erratic flow behavior of the polymer melts. In order to study this problem, a constant‐rate, capillary rheometer was used to study the melt flow over a wide range of shear rates. These data demonstrate that many high‐density polyethylenes exhibit a discontinuous shear‐stress shear‐rate curve; that is, under certain conditions the observed load oscillates “between two values differing by about 15%”. This region of unstable melt flow is not necessarily allied with melt fracture although it is dependent on molecular weight and melt temperature. Unstable melt flow occurs at lower shear rates with a decrease in the melt index (increase in molecular weight) or melt

ISSN:0032-3888    

DOI:10.1002/pen.760030106

出版商:Society of Plastics Engineers, Inc.    

年代:1963

数据来源: WILEY

摘要:

AbstractThe effect of polymers with conjugated bonds, namely polyphenylvinylene, phenylacetylenep‐diethinylbenzene copolymer and thermally dehydrochlorinated polyvinylchloride, upon the stability of polyvinylchloride suspensions has been investigated. It has been shown that polymers with conjugated double bonds are efficient inhibitors of the thermal dehydrochlorination of polyvinylchloride. The most active inhibitor, polyphenylvinylene, is not light stabilize

ISSN:0032-3888    

DOI:10.1002/pen.760030107

出版商:Society of Plastics Engineers, Inc.    

年代:1963

数据来源: WILEY

摘要:

AbstractAn expression for the “average” viscosity of a polymeric material realized during an injection molding shot is developed. From this expression certain rheological quantities are taken which should better express ease of molding than do conventional testing methods. Comparison is made between actual molding experience and quality as predicted by the new met

ISSN:0032-3888    

DOI:10.1002/pen.760030108

出版商:Society of Plastics Engineers, Inc.    

年代:1963

数据来源: WILEY

摘要:

AbstractAn expression for the “average” viscosity of a polymeric material realized during an injection molding shot is developed. From this expression certain rheological quantities are taken which should better express ease of molding than do conventional testing methods. Comparison is made between actual molding experience and quality as predicted by the new met

ISSN:0032-3888    

DOI:10.1002/pen.760030109

出版商:Society of Plastics Engineers, Inc.    

年代:1963

数据来源: WILEY

摘要:

AbstractIt is demonstrated that the bonding characteristics of commercial liquid adhesive primers made from nitrile rubbers and phenol‐formaldehyde polymers, cured by means of hexamethylenetetramine can be quite sensitive to the presence of small amounts of excess water and ammonia. The added water partially decomposes the hexamethylenetetramine to formaldehyde and ammonia, the concentration of the latter thus increasing to such a point as to promote a lower temperature curing of the phenolic resin. Restoration of the original adhesive properties can be attained by the addition of reagents which remove either the water or the ammonia, or both, from the adhesive. Examples of such reagents are certain organic acids, anhydrides and peroxides. The addition of these reagents has been found to reactivate and increase greatly the useful lives of nitrile‐phenolic liquid adhesive primers containing hexamethylenetetram

ISSN:0032-3888    

DOI:10.1002/pen.760030110

出版商:Society of Plastics Engineers, Inc.    

年代:1963

数据来源: WILEY

摘要:

AbstractMonomers for which the necessary information was obtained for comparison included the following: styrene, α‐methylstyrene,cisandtrans‐propenylbenzene, allylbenzene, m‐methylstyrene, p‐methylstyrene, o‐, m‐, and p‐chlorostyrene, 2,3‐, 2,4‐, 2,5‐, 2,6‐, 3,4‐, and 3,5‐dichlorostyrene, p‐ethylstyrene, and p‐tert‐butylstyrene. In both free radical and ionic copolymerizations involving similar monomers, plots of the logarithms of the relative reactivities of several substituted styrenes toward the styrene and methyl methacrylate radicals versus the differences existing between the exaltations of substituted styrenes and the exaltation of styrene were strikingly similar to those in which Hammett's sigma values for the styrene substituents were plotted against the relative reactivi

ISSN:0032-3888    

DOI:10.1002/pen.760030111

出版商:Society of Plastics Engineers, Inc.    

年代:1963

数据来源: WILEY