ISSN:0032-3888    

DOI:10.1002/pen.760140302

出版商:Society of Plastics Engineers, Inc.    

年代:1974

数据来源: WILEY

摘要:

AbstractUltimate properties in polymeric solids strongly depend on thermomechanical history. We have shown that the polymer structure which depends on thermomechanical history can be quantitatively described by the relative amounts of enthalpy and entropy. The excess enthalpy decreases upon annealing and increases under the tensile stress. The increase in excess enthalpy reduces the relaxation time; thus a local brittle‐to‐ductile transition may be induced by stress concentration. It follows that in a well‐annealed material, this transition is more difficult to induce. Effects of molecular weight and orientation are also discussed in terms of dissipation of strain energy as the condition required for the strength of polymeric s

ISSN:0032-3888    

DOI:10.1002/pen.760140303

出版商:Society of Plastics Engineers, Inc.    

年代:1974

数据来源: WILEY

摘要:

AbstractGlassy, amorphous thermoplastics experience a nearly universal susceptibility to crack and craze formation in the combined presence of stress and a chemical environment. This susceptibility has been evaluated for styrene‐acrylonitrile copolymers according to the factors which effect craze initiation and those which limit the rates of flaw propagation. Molecular weight, styrene‐acrylonitrile ratio, rubber content, and rubber phase morphology are variables which were found to affect flaw initiation and propagation. Fundamental characterization of the chemical parameters which control the initiation of craze formation in polysulfone and polycarbonate is also presented. In particular, “3‐dimensional” solubility parameters have been observed to be a reasonable means of characterizing susceptibility to environmental stress

ISSN:0032-3888    

DOI:10.1002/pen.760140304

出版商:Society of Plastics Engineers, Inc.    

年代:1974

数据来源: WILEY

摘要:

AbstractTwo overriding characteristics for major applications of plastics in consumer products are: —the need for high volume production and—their exposure to hostile environments.Successful application and continued growth for plastics in these products requires knowledgeable prediction of performance in the process to produce the plastic part and in the environments to which it will be exposed during the product's lifetime. Progress on establishing relationships between material properties and structure are described with emphasis on response to melt process conditions and behavior when exposed to hostile environments.Commercial plastics and the processes by which they are converted into useful applications are complex systems. A multitude of interacting variables must be dealt with in order to achieve successful implementation in commercial products. Specific examples are discussed in the area of processing for non‐Newtonian flow characteristics and overt effects in injection molding and extrusion, tailoring of polymers within established rheological limits and the influence of melt processing on physical and mechanical properties. The influence of application environments is discussed and specific examples are given for environmental stress cracking, stress‐environment embrittlement and the effects of hot water solutions on polymer

ISSN:0032-3888    

DOI:10.1002/pen.760140305

出版商:Society of Plastics Engineers, Inc.    

年代:1974

数据来源: WILEY

摘要:

AbstractThe flexural creep compliance of a propylene copolymer was determined as a function of time and temperature using stresses of less than 700 psi. Equilibrium compliances of 2.82 × 10−5, 3.80 × 10−5, and 4.47 × 10−5in2/lb at 75, 140, and 168°F respectively, are predicted. The data are used to characterize a flanged pressure chamber. Deflections due to flange opening deformation modes predicted for life times in excess of 40 years indicate the need for flange rein

ISSN:0032-3888    

DOI:10.1002/pen.760140306

出版商:Society of Plastics Engineers, Inc.    

年代:1974

数据来源: WILEY

ISSN:0032-3888    

DOI:10.1002/pen.760140307

出版商:Society of Plastics Engineers, Inc.    

年代:1974

数据来源: WILEY

摘要:

AbstractOften the first step in the solution of problems concerning the use of plastics involves the detailed characterization of a particular resin. Typically, a commercial plastic is composed not only of the basic resin but also of many additional additives. These additives may be such things as impact modifiers, plasticizers, flame retardants, and molding lubricants. In our laboratory we have developed thermoanalytical techniques for the determination of the morphology and composition of these multiphase materials. Specifically, we have quantitatively analyzed an ABS resin for not only the amount of SAN and BD but also the concentration of a molding lubricant (ML) in the resin. The concentration of BD and SAN was estimated calorimetrically from ΔCpmeasurements atTg, and the ML level was calculated from ΔHfdeterminations. In addition, the shifts inTgof both the BD and SAN phases of the ABS were studied as a function of diluent concentration. The diluents in these resins are residual monomers or other “impuriti

ISSN:0032-3888    

DOI:10.1002/pen.760140308

出版商:Society of Plastics Engineers, Inc.    

年代:1974

数据来源: WILEY

摘要:

AbstractThe mechanism of weathering degradation of polyolefins is discussed. Variations in spectral radiation, temperature, density, polymer absorption spectra, orientation, and sample thickness are related to property deterioration. Organic ultraviolet stabilizers, zinc oxide stabilization, and UV catalyzed degradation are briefly reviewed.

ISSN:0032-3888    

DOI:10.1002/pen.760140309

出版商:Society of Plastics Engineers, Inc.    

年代:1974

数据来源: WILEY

摘要:

AbstractFlow patterns have been observed during the injection molding of rheologically characterized low‐density polyethylene and polystyrene melts under various molding conditions. Some studies of high‐density polyethylene were also carried out. Various mold designs were included in the study and the flow patterns investigated under both isothermal and cold cavity wall conditions. In addition to investigating injection molding of single polymer melts, flow patterns in the sandwich molding of polyethylene and polystyrene were stud

ISSN:0032-3888    

DOI:10.1002/pen.760140310

出版商:Society of Plastics Engineers, Inc.    

年代:1974

数据来源: WILEY

摘要:

AbstractThe transport equations for a power law fluid are used to solve the transient and non‐isothermal problem of filling a disk‐shaped cavity. Using the results obtained it is possible to predict gate pressures, fill times and short shots. Furthermore, the velocity and temperature fields can be obtained throughout the filling process. This information specifies the formation of a frozen surface layer during filling. Rigid PVC was primarily used in the simulations, but some results are also given for linear polyethylene, nylon 6–6, ABS and polyst

ISSN:0032-3888    

DOI:10.1002/pen.760140311

出版商:Society of Plastics Engineers, Inc.    

年代:1974

数据来源: WILEY