摘要:

AbstractIt is the objective of this paper to demonstrate the applicability of cold compaction molding followed by a sintering treatment to the processing of polystyrene powders. The influence of pressure, compaction speed, and peak pressure dwell time on the green (as compacted) density and the green tensile strength, as well as the effect of sintering on the tensile strength and dimensional change, were evaluated. The resulting data indicate that room temperature compaction alone is insufficient to provide adequate tensile strength for the compacts. Sintering the green compacts at temperatures of 150 to 173°C markedly improves the tensile strength while simultaneously causing a thickness change in the compacts. This thickness change results from gas evolution, pore shrinkage, and viscoelastic recovery of the residual stresses induced by pressure. For compacts of 0.225 in. thickness, an optimum sintering treatment of 173°C for 30 mins is recommended to provide a tensile strength of 4,000 psi and a thickness change of less than + 7 percent. Coining (repressing) the green compacts does not appreciably affect the sintered strength. However, a finer particle size improves the sintered properties. A review of the literature on the flow behavior of polystyrene suggests that a non‐Newtonian viscous flow mechanism is followed by a Newtonian one as sintering progres

ISSN:0032-3888    

DOI:10.1002/pen.760160802

出版商:Society of Plastics Engineers, Inc.    

年代:1976

数据来源: WILEY

摘要:

AbstractThe influence of matrix properties on randomly oriented glass fiber epoxy composites has been studied. It is shown that an increased ductility (flexibility) of the matrix does not result in greater elongation to failure of the composite under tensile and flexural loads. The tensile (and flexural) strength and the modulus of elasticity are decreased as the ductility of the resin is increased. It is concluded that since the matrix material is subjected to a triaxial state of stress when the composite specimen is subjected to uniaxial loads, the effect of matrix modulus, Poisson's ratio, and yield strength are more important than the matrix ductility measured under uniaxial stress. The effect on mechanical properties of various surface treatments applied to the fibers is also investigated. Finally, scanning electron micrographs are presented showing matrix cracks, fiber debonding, and fiber pull‐ou

ISSN:0032-3888    

DOI:10.1002/pen.760160803

出版商:Society of Plastics Engineers, Inc.    

年代:1976

数据来源: WILEY

摘要:

AbstractThe techniques of thermogravimetric and derivative thermogravimetric analyses have been applied to the determination of temperatures and heats of decompositions of four ethylene/propylene rubbers and seven cross‐linked polyethylenes in nitrogen. These materials are commonly used in the wire and ruble industry as dielectric insulation. The polymers were found to decompose in at least three overlapping stages. Each stage has an activation energy characteristic of the process. Differential thermal analysis was significantly less useful in this study due to the conflict of the endothermal heat of vaporization and the exothermal heat of decompositio

ISSN:0032-3888    

DOI:10.1002/pen.760160804

出版商:Society of Plastics Engineers, Inc.    

年代:1976

数据来源: WILEY

摘要:

AbstractData on the solubility and diffusion of vinyl chloride monomer (VCM) in PVC resin powders have been combined with published solutions of Fick's diffusion equation to yield predictions of the amount and rate of loss of residual VCM (RVCM) from rigid PVC pipe under storage and service conditions. The principal factors controlling VCM migration are the initial VCM content, thickness of the PVC section, temperature and the age of the PVC product. Analysis Solutions are presented for RVCM loss from freshly exturded pipe (uniform VCM concentration) into either the storage environment or the pipe contents. From these solutions, estimates are made for the real‐world situation of closed‐system service following variable storage periods. The validity of this approach for rigid PVC pipe in water‐service is supported by reasonable agreement between its predictions and experimental laboratory data on the VCM content of water stored in PVC pipes. Both the predictive model and experimental data indicate that PVC pipe containing ≤ mg/kg (1 part per million) residual VCM will result in VCM concentrations in water of less than 0.002 mg/kg ‐ under any expected service c

ISSN:0032-3888    

DOI:10.1002/pen.760160805

出版商:Society of Plastics Engineers, Inc.    

年代:1976

数据来源: WILEY

摘要:

AbstractThe great strides made over the last two decades allow the design engineer to predict performance characteristics in solid plastics. The current state of the art in structural foam is somewhat more primitive. Theories and basic design procedures as well as measurement of mechanical properties require evaluation. Because of the deep penetration of structural foam into the marketplace, especially in the large consumer areas of furniture and automotive applications, design techniques are required to cover the many application. This paper reviews briefly the basic information needed for structural foams, compares empirical relations and theoretical models, and discusses some inherent limitations of foamed materials.

ISSN:0032-3888    

DOI:10.1002/pen.760160806

出版商:Society of Plastics Engineers, Inc.    

年代:1976

数据来源: WILEY

摘要:

AbstractStringent government environmental regulations applied to the electroplating industry have spurred a search for alternative means of providing chromium coatings on plastics. Vapor deposition, an established and extensively utilized process for applying aluminum coatings on plastics, is quite naturally being investigated as an alternative process. Vapor deposited chrome has a darker cast than electrochrome, and a great‐number of materials are being investigated to find a color matching substitute that will stand up under severe environmental conditions. Among these are the 300 and 400 series stainless steels, nichrome, and other alloys. It has been found, with proper surface preparation, that highly adherent and specular stainless steel coatings/can be obtained oh plastics using filament and boat evaporation techniques. The coatings resemble a highly polished version of the parent metal and bear a striking resemblance to chrome. However, some type of clear topcoat is required to provide abrasion resistanc

ISSN:0032-3888    

DOI:10.1002/pen.760160807

出版商:Society of Plastics Engineers, Inc.    

年代:1976

数据来源: WILEY

摘要:

AbstractThe solid‐state extrusion of polypropylene by hydrostatic pressure has been investigated at four different temperatures: 25, 50, 75, and 100°C. The pressure to effect extrusion was found to be essentially a linear function of the extrusion ratio at each temperature, while the magnitude of the extrusion pressure, for any given extrusion ratio, decreased appreciably with increasing temperature. With increase in extrusion‐ratio, the polypropylene extrudates became increasingly transparent. After passing through the extrusion dies; the Sample showed some elastic recovery. The amount of this recovery decreased with increasing extrusion ratio, X‐Ray diffraction measurements taken before and after extrusion showed reduction in sharpness of the crystalline Peaks. Differential, scanning calorimetric measurements, on the other hand, indicate that the relative heat of fusion of the extrudates increases with the extrusion ratio at each extrusion temperature. It also increases with extrusion temperature for a given ratio. Tensile stress‐strain tests were made at various hydrostatic pressure levels on the extrudates obtained at 25°C and the extrusion ratio of 2.8. Unlike on the virgin sample of polypropylene, ho yield maximum was observed on the extrudate sample at all pressures investigated. However, the effects of pressure on the relative increase in the yield stress‐and the modulus of the extrudate are comparable to those of original, unorien

ISSN:0032-3888    

DOI:10.1002/pen.760160808

出版商:Society of Plastics Engineers, Inc.    

年代:1976

数据来源: WILEY

摘要:

AbstractThe ultimate strength of polymer concrete was investigated utilizing epichlorohydrin/bisphenol A‐type epoxy resin. Parameters were tested in an effort to conclude how variation of a specific parameter would affect the compressive strength of the polymer concrete. The parameter testing included studies to determine the effect of the polymer loading; the catalyst; the exothermic reaction; aggregate type, gradation and moisture content; curing age; and aggregate additives of portland cement and lime‐stone pow

ISSN:0032-3888    

DOI:10.1002/pen.760160809

出版商:Society of Plastics Engineers, Inc.    

年代:1976

数据来源: WILEY

摘要:

AbstractA method is presented for predicting rheological characteristics, such as shear dependent (non‐Newtonian) viscosity and components of linear oscillatory (complex) response functions for polyethylene melts from molecular weight distribution data obtained from gel permeation chromatographic (GPC) analysis. The results are compared with measured values of the rheological functions obtained from a variety of instruments over an extensive range of shear rates‐and frequencies. The agreement between predicted and measured rheological functions is quite good for high density resins. However, for a low density resin the agreement is not as good, although still reasonable over a considerable range of conditions. It is concluded that the quality of the GPC data is the key factor in the degree of success of the met

ISSN:0032-3888    

DOI:10.1002/pen.760160810

出版商:Society of Plastics Engineers, Inc.    

年代:1976

数据来源: WILEY

摘要:

AbstractExperimental studies of injection molding of polymer melts have classified two regimes of mold filling–simple filling and jetting. In this paper we have examined a wide range of polymer melts and mold designs in an attempt to devise a criterion for the transition between these regimes. This criterion is found to be related to the extrudate swelld, gate diameterD, and small cavity dimension at the gateh. For isothermal mold filling, ifd/hexceeds 1.0, the‐melt will contact the mold, stick to it, and induce a simple mold filling regime. The variation in behavior in vertical and horizontal mold filling is considered, as is the influence of barriers near the gate. For the non‐isothermal mold case, the manner of filling is similar, and the criterion for jetting remains the same, The die swell behavior in the non‐isothermal case is

ISSN:0032-3888    

DOI:10.1002/pen.760160811

出版商:Society of Plastics Engineers, Inc.    

年代:1976

数据来源: WILEY