摘要:

AbstractThe importance of data produced by gel permeation chromatography (GPC) in polymer engineering is emphasized. The steps involved in deriving a differential molecular weight distribution curve (dMWD) from the chromatogram obtained by GPC are outlined. Each step is described, indicating its importance. Several viscosity‐molecular weight relationships, useful in the production of relevant calibration curves from the polystyrene calibration, are included. The presentation of results and experimental procedures are give

ISSN:0032-3888    

DOI:10.1002/pen.760130602

出版商:Society of Plastics Engineers, Inc.    

年代:1973

数据来源: WILEY

摘要:

AbstractThe tensile strength, fracture energy, and impact strength of ABS reinforced with discontinuous crystalline fibers such as FybexDu Pont trademark.can be controlled by manipulating fiber‐matrix interfacial adhesion. In “good bonding” situations composite tensile strength, thermal expansion coefficient, and elastic moduli are significantly improved over the unfilled resin. The excellent impact strength of unreinforced ABS can be retained by lowering the fiber‐matrix interfacial adhesion. This results in a corresponding reduction in the improvements in tensile and flexural strength. However, the elastic moduli and thermal expansion coefficients are relatively insensitive to changes in adhesion. Consequently, a material with high modulus (>500,000 psi), high Izod impact resistance (7.0 ft‐lb/in.), and low expansion coefficient (3.0 × 10−5in./in./°F) can be obtained. A material with this unique combination of properties should find use in large parts such as camper tops, truck grilles, and snowmobile bodies.Fiber‐matrix adhesion was measured directly by an x‐ray analysis technique which could be employed because of the fiber's crystallinity and unique growth habit. This independent measurement allowed a correlation between bonding and composite properties. The interfacial bond strength was manipulated by a variety of fiber coatings an

ISSN:0032-3888    

DOI:10.1002/pen.760130603

出版商:Society of Plastics Engineers, Inc.    

年代:1973

数据来源: WILEY

摘要:

AbstractDifferential thermal analysis (DTA) is well known for measuring temperatures and heats of physical and chemical transitions in materials. Recent development work on improved stabilization systems for polyolefin wire insulations has required fast procedures for measuring the performance of stabilization systems. Isothermal DTA procedures have been developed into routine tools for measuring stability of polyolefins by determining the oxidative induction time at elevated temperatures.Oxidative induction time has been used to study the stability of polyethylene and polypropylene in raw material form and on wire. The dependence on temperature and antioxidant concentration have been measured. Effects of oxidation catalysts, catalyst deactivators and various environmental exposures are readily observed. Techniques and apparatus have been developed for simultaneous testing of a multiplicity of samples, providing for economical large scale use of the method.

ISSN:0032-3888    

DOI:10.1002/pen.760130604

出版商:Society of Plastics Engineers, Inc.    

年代:1973

数据来源: WILEY

摘要:

AbstractThe effect of cold rolling on the mechanical properties of polymers, viz., acetal, nylon 66, poly(vinyl chloride) and polycarbonate has been studied. The yield strength, Young's modulus, and hardness increase with increasing cold work, except for a slight drop in these properties at low values of cold work. The ductility increases with rolling to a maximum and drops with further reduction. At the same time, the tensile strength increases continuously with rolling. This conspicuous occurrence of the increase in ductility with a simultaneous increase in tensile strength for polymers, unlike that in metals, is explained considering the morphological changes produced in polymers upon cold rolling. It is shown that this typical behavior is not due to the unique loading or heating and cooling cycle involved in the rolling process.

ISSN:0032-3888    

DOI:10.1002/pen.760130605

出版商:Society of Plastics Engineers, Inc.    

年代:1973

数据来源: WILEY

摘要:

AbstractDifferential thermal analysis offers a convenient and rapid way of determining stabilization levels in polyolefin compositions. Since it is normally used at temperatures in the fabrication range, it provides a direct readout of processing stability. At the same time, because the chemistry of the polymer system at these temperatures may be quite different from that at normal use temperatures, judgment must be exercised in attempting to extrapolate high temperature data. New factors can come in at either end of the temperature range which are inoperative at the other extreme.The experimental procedures used are described, and the special precautions necessary for operation down to the 140–150°C range indicated. Problems arising from sample inhomogeneities are discussed, and the critical importance of stabilizer migration in the solid state pointed out, including invalidation of extrapolation down to normal temperatures of data taken above the melting ran

ISSN:0032-3888    

DOI:10.1002/pen.760130606

出版商:Society of Plastics Engineers, Inc.    

年代:1973

数据来源: WILEY

摘要:

AbstractSurface microscopy studies have revealed the phase separation and exudation of a phenol type of antioxidant [4,4′‐thiobis (3‐methyl‐6 tert. butyl phenol)] from polyethylene at concentrations of 0.08 percent by weight. The equilibrium solubility of the antioxidant in polyethylene was estimated to be less than 0.01 weight percent at room temperature.About 70 percent of the antioxidant was expelled from a thin polyethylene film after storage for three days at 70°C. Since the initial concentration of the stabilizer is typically 0.10 percent of the polymer by weight, the antioxidant exudation can lead to a serious shortening of the expected life of the polymer. Prediction of lifetime by accelerated aging tests must account for the depletion of the stabilizer by exudation. The life of stabilized samples should be measured at concentrations which do not exceed the solubility limit of the antioxidant in polyethylene at its use tem

ISSN:0032-3888    

DOI:10.1002/pen.760130607

出版商:Society of Plastics Engineers, Inc.    

年代:1973

数据来源: WILEY

摘要:

AbstractRelations describing the time dependence of pressure loss in pressurized plastic containers are presented and discussed. These relations are expected to be useful in predicting the shelf life performance of pressurized plastic containers in applications such as aerosol and carbonated beverage containers. The time dependence of pressure loss in pressurized plastic containers is shown to be dependent on at least three independently contributing factors, namely gas absorption, gas permeation, and material viscoelastic characteristics. The influence of these three qualities is shown to be time dependent and expressions are presented which allow the relative importance of each to be assessed in terms of quantities that are conveniently measured in the laboratory. The pitfalls associated with defining quantitatively the effectiveness of a plastic barrier material as predicted by a steady state analysis is discussed. It is shown that such steady state analysis may be extremely misleading and may not necessarily be a measure of a material's time dependent qualities.

ISSN:0032-3888    

DOI:10.1002/pen.760130608

出版商:Society of Plastics Engineers, Inc.    

年代:1973

数据来源: WILEY

摘要:

AbstractThe thermomechanical spectra (∼0.5 → 1 cps) of systematically related polyimides synthesized from four aromatic dianhydrides and eleven aromatic diamines are discussed with respect to structure‐property relationships and cure. In displaying two main transitions,TgandTβ, most of the polymers behave as amorphous materials such as polymethylmethacrylate. A different mechanism for the relaxations is invoked which involves more intermolecular interaction for those polymers (from pyromellitic dianhydride) which give more complex behavior. Difficulties in obtaining structure‐property relationships in the field of high temperature rigid polymers are discussed in terms of defects in molecular structure, the effect of vitrification in freezing out reactions during cure, different chemical reactivities of the reactive precursor polyamic acids, and the effects of thermal reactions which occur in the vicinity of the glass transition

ISSN:0032-3888    

DOI:10.1002/pen.760130609

出版商:Society of Plastics Engineers, Inc.    

年代:1973

数据来源: WILEY

摘要:

AbstractPronounced effects of thermal treatment on the properties of graphite fiber/polycarbonate and glass fiber/polycarbonate composites have been demonstrated and explained. At 20 volume percent loading of random‐in‐a‐plane, discontinuous fibers, both specimen strength and modulus in both fiber systems were found to increase dramatically upon molding above 260–265°C, whereas only the graphite system was further improved by subsequent annealing. In the latter case, property improvement is due to generation of a crystalline innerlayer at the interface, which apparently transfers the stresses more effectively from fiber to fiber. Regardless of the type of fiber, molding at 275°C (slightly above 260–265°C, the melting point of crystalline polycarbonate) results in improved properties due to better wetting of the fibers by the resin. Hot forming of graphite reinforced polycarbonate composites between the molding and annealing steps takes advantage of the higher processability of the unannealed material in addition to providing increased modulus and strength in the final mo

ISSN:0032-3888    

DOI:10.1002/pen.760130610

出版商:Society of Plastics Engineers, Inc.    

年代:1973

数据来源: WILEY

摘要:

AbstractIt has been shown that the only way to predict the size of the PTC effect displayed by a crystalline polymer when filled with conductive particles is through the knowledge of the glass transition point of the polymer. The size of the PTC anomaly is found to decrease sharply with rise in glass transition temperature and for a polymer to be a useful PTC material its glass transition must be below 0°C. It has not been possible to explain this relationship by any of the current theories of the PTC mechanism in filled polymers

ISSN:0032-3888    

DOI:10.1002/pen.760130611

出版商:Society of Plastics Engineers, Inc.    

年代:1973

数据来源: WILEY