摘要:

AbstractThe results of an experimental study of melt fracture using polystyrene samples of narrow and broad molecular weight distribution are presented. The weight average molecular weight (M̄w) ranged from 9.72 × 104to 1.80 × 106and the distribution breadth M̄w/M̄ηfrom 1.06 to 9.21. The critical shear stress varies linearly with 1/M̄w, increases slightly with temperature and is independent of the distribution of molecular weights. This type of behavior is satisfactorily explained in terms of Graessley's entanglement

ISSN:0032-3888    

DOI:10.1002/pen.760110102

出版商:Society of Plastics Engineers, Inc.    

年代:1971

数据来源: WILEY

摘要:

AbstractThe synthesis of graft copolymers by anionic polymerization techniques is reviewed. Two basic procedures are described. In one a polymer having a reactive end‐group is prepared and allowed to react with another polymer having suitable functional groups. In the second procedure, anions are generated on a preformed polymer backbone and used to initiate the polymerization of subsequently added monomer

ISSN:0032-3888    

DOI:10.1002/pen.760110103

出版商:Society of Plastics Engineers, Inc.    

年代:1971

数据来源: WILEY

摘要:

AbstractThe interactions of γ‐aminopropyltriethoxy silane (A‐1100), γ‐methacryloxytrimethoxy silane (A‐174), γ‐glycidoxytrimethoxy silane (A‐187), and ethyltriethoxy silane (A‐15) with silica surfaces have been studied by means of infrared spectroscopy. The results indicate that the major force holding the silane to the silica surface after application from dilute solutions is primary chemical bonding. These bonds are formed by a condensation reaction between silanols on the hydrolyzed form of the silane and hydroxyl groups on the silica surface. In the case of the amino‐silane (A‐1100), hydrogen bonding was found to exist but was of minor importance in bonding the silane to the surface. In studying the effects of the addition of water, acetic acid, or n‐propylamine to various silane treating solutions, it was found that n‐propylamine has a unique catalytic effect on the condensation reaction. This catalytic effect explains the observation that γ‐aminopropyltriethoxy silane is more reactive than the other silanes studied. It is felt that silanes not containing an amine group can be made more effective if they are applied in the pr

ISSN:0032-3888    

DOI:10.1002/pen.760110104

出版商:Society of Plastics Engineers, Inc.    

年代:1971

数据来源: WILEY

摘要:

AbstractAn apparatus was designed and built which allowed an investigation concerning the morphology and kinetics of crystallization of a deformed polybutene‐1 melt. The polymer was quenched from a temperature above its melting point to one of two crystallization temperatures. The supercooled melt was then sheared and allowed to crystallize isothermally while the internal stress in the melt was continuously recorded. A polarizing microscope was employed for the simultaneous study of the resulting morphological changes. By properly accounting for thermal contractions within the apparatus caused by the quenching operation, as well as the imposed shear strain, a strain history of the polymer during crystallization was developed. From this strain history and the assumption that the volume contraction resulting from crystallization was isotropic, approximate kinetics of crystallization in a deformed polymer melt were determine

ISSN:0032-3888    

DOI:10.1002/pen.760110105

出版商:Society of Plastics Engineers, Inc.    

年代:1971

数据来源: WILEY

摘要:

AbstractThe forces required to compress billets of crystalline polymers below their melting points were determined and related to the initial billet dimensions and amount of deformation. The studies involved the use of three high‐density polyethylenes and an acetal copolymer. The results were found to obey an equation derived from plasticity theory using, at each temperature and for each material, a single parameter very nearly equal to the yield strength determined in ordinary tensile tests, and having the same temperature dependence. An empirical equation that describes the pressure required to form cups by backward extrusion of metal billets is also successful for the same process with polymers, using the yield parameter from the compression experiments. Cold working causes a high degree of orientation, increased clarity, and greatly increased tensile strengt

ISSN:0032-3888    

DOI:10.1002/pen.760110106

出版商:Society of Plastics Engineers, Inc.    

年代:1971

数据来源: WILEY

摘要:

AbstractA falling coaxial cylinder viscometer was used to measure the melt flow behaviour of a commercial polystyrene withMw260,000. The shear stress region extended down to 0.6 × 104dynes/cm2and shear rates were as low as 3 × 10−2sec−1at 186°C. The shear rate‐shear stress plots were linear at low shear stresses with slopes (differential viscosities) of 3.3 × 105poises at total shear less than 120 units and decreasing differential viscosity with higher total shear. The flow curves at relatively low total shear were initially dilatant and became pseudoplastic with increasing shear stress. The inflection point represents a Newtonian apparent viscosity, which agrees fairly well with literature values for polystyrenes of the sameMw. Newtonian apparent viscosity is characteristic of a point value of shear stress and shear rate and is not necessarily a plateau region. Observation of a Newtonian region with decreasing shear stress or shear rate does not prove that this flow regime persists unchanged to zero values of the experimental parameter. The existence and magnitude of the Newtonian apparent viscosity reflects shear history of the polymer as well as its constitution and molecular weight dis

ISSN:0032-3888    

DOI:10.1002/pen.760110107

出版商:Society of Plastics Engineers, Inc.    

年代:1971

数据来源: WILEY

摘要:

AbstractHolographic reflective interference patterns arising from a small displacement of the surface of polymer solids provide a very sensitive means for detecting the internal stress related to molecular orientation, as well as measuring very small time dependent deformations not accessible by conventional means. Applicability of this technique using 6328Å laser light on various mechanical studies in polymeric solids is discussed

ISSN:0032-3888    

DOI:10.1002/pen.760110108

出版商:Society of Plastics Engineers, Inc.    

年代:1971

数据来源: WILEY

摘要:

AbstractThe longitudinal strengths of unidirectional discontinuous fiber composites have been calculated based on the concept of perturbation effect and the distortional energy criterion, utilizing the finite‐element method. The theoretical results thus obtained are compared with the experimental data as well as the results of shear lag analysis for tungsten‐copper, boron‐aluminum, glass‐epoxy and boron‐epoxy composites. Based on the Jackson‐Cratchley equations, modified for discontinuous fibers, a formula is also proposed for calculating the strengths of randomly oriented discontinuous fiber composites. The results calculated from this formula are compared with the experimental data for aluminum oxide‐aluminum‐silicon and glass

ISSN:0032-3888    

DOI:10.1002/pen.760110109

出版商:Society of Plastics Engineers, Inc.    

年代:1971

数据来源: WILEY

摘要:

AbstractA new analytical technique, differential thermal analysis using high frequency dielectric heating (DTA/HF), has been developed which senses the rate and extent of the enthalpy change accompanying curing. These two parameters relate simply and quantitatively to curing reaction kinetics.In DTA/HF cylindrical samples of uncured elastomers, 2‐in. in diam and about 1‐in. high, enclosed in glass rings and covered, are heated in a high frequency (86 mc) electrical field simultaneously with an identically‐shaped precured reference disc of the same elastomer. Both sample and reference are clamped securely between 3 × 5‐in. rectangular output electrodes. The sample is cured isometrically under pressure generated by thermal expansion. Temperatures at the core of the sample and reference are monitored continuously using ungrounded junction thermocouples with stainless steel probes; both sample temperature and temperature differences between sample and reference are recorded.To test the validity of DTA/HF it was first applied to the dicumyl peroxide (DCP) curing of several cis‐1,4‐polyisoprene calcium carbonate mixtures for which reaction mechanisms and reaction kinetic data a

ISSN:0032-3888    

DOI:10.1002/pen.760110110

出版商:Society of Plastics Engineers, Inc.    

年代:1971

数据来源: WILEY

摘要:

AbstractA previous paper described the theory and equipment of Differential Thermal Analysis using High Frequency Dielectric Heating, DTA/HF. Curing studies using DTA/HF on cis‐1,4‐polyisoprene rubber filled with 50 phr of CaCO3and containing from 1.5 to 4.5 phr of dicumyl peroxide (DCP) curative indicated that below about 185°C, the curing reaction was first order with respect to DCP; the mean activation energy was 32.6 kcal/mole; and the heat of reaction ranged from 60 to 80 kcal/mole DCP. These results are in agreement with published results. Above 185°C both thermodynamic and kinetic evidence implied that the reaction mechanism changed; the first order peroxide decomposition no longer controlled the overall rate of reaction.The curing of both stereo styrene‐butadiene rubber (SBR) and cis‐1,4‐polybutadiene rubber (BR) containing 50 phr of CaCO3and 0.5 phr of DCP was found to follow first order kinetics as expected. The magnitude of the heat of curing was used to determine the frequency of a vinyl propagation‐type cross‐linking reaction. Eight to 36 crosslinks per molecule of DCP were obtained. This reaction became more extensive at high temperature, in agreement with pu

ISSN:0032-3888    

DOI:10.1002/pen.760110111

出版商:Society of Plastics Engineers, Inc.    

年代:1971

数据来源: WILEY