摘要:

AbstractPlates of bisphenol‐A polycarbonate and poly(methyl methacrylate) have been quenched in ice water from temperatures slightly above their glass transition temperatures. Residual stresses are thus created, Measurement of these residual stresses has been accomplished by the “layer removal” method and the stress distributions through the thickness are presented. Compressive stresses, approximately 3000 psi, exist at the surface while tensile stresses‐of at least 1000 psi exist in the interior. It is shown that these residual stresses can influence the notched Izod impact strengths for polycarbonates. The mechanism is thought to be suppression of craze initiation in advance of the notch due to the presence of residual compressive stresses for specimens notched prior to quenching. In the case of poly(methyl methacrylate), it is shown that compressive residual stresses at the surface can cause plastic yielding to occur in bending experiments resulting in permanent deformation and greater energy abs

ISSN:0032-3888    

DOI:10.1002/pen.760161202

出版商:Society of Plastics Engineers, Inc.    

年代:1976

数据来源: WILEY

摘要:

AbstractThe build‐up of internal stresses in injection molded parts is due to the combined effect: of a low thermal conductivity (diffusivity) of normal polymer melts and their rapid cooling in the mold cavity. The present paper shows that increasing the thermal diffusivity of the polymer by the addition of relatively small amounts of metallic fillers resulted in a substantial reduction in the internal stress level. The filler content was of the order of a few percent by volume. The average internal stress (σi) was determined by a stress relaxation method. The modulus, tensile strength, and other mechanical properties of the samples were not influenced by the filler addition. The impact strength, however, decreased sharply, as no adhesion pro‐motors were used. The observed improvements in mold shrinkage, thermal shrinkage, hardness, and stress‐cracking tendency could be related to a decreased σilevel. In comparative experiments with other fillers (MgO, glass powder), a good correlation was found between the σilevel and the thermal diffusivity of th

ISSN:0032-3888    

DOI:10.1002/pen.760161203

出版商:Society of Plastics Engineers, Inc.    

年代:1976

数据来源: WILEY

摘要:

AbstractA new rheometer has been developed to measure the extensional viscosity of molten thermoplastics at typical extrusion temperatures. It is at the same time versatile and easy to operate. One end of the test specimen is held in a fixed position by an oil‐cooled chimp mounted on the end of a force transducer. The other end of the specimen is held by, a moving, oil‐cooled chimp. The moving clamp is suspended from a carriage mounted on a ball nut which travels on a long lead screw. The lead screw is driven by an electric motor operating through a gear box, and its speed can be controlled to produce either a constant stress (creep) or a constant strain‐rate (stress growth) experiment. Experimental results have verified that in the “constant strain rate” mode the strain rate does rise rapidly to a constant level. Measurements on several polyethylene resins indicated that the extensional viscosity rises with strain rate at low str

ISSN:0032-3888    

DOI:10.1002/pen.760161204

出版商:Society of Plastics Engineers, Inc.    

年代:1976

数据来源: WILEY

摘要:

AbstractTrifunctional poly‐ε‐caprolactone polyol was polymerized with a chain‐extended 1,6‐hexane diisocyanate, and the rheology followed by cone and plate flow. Viscosity was found to be independent of shear rate up to at least 102N.s/m2(103poise) and 30s−1. Extent of reaction was monitored by a periodic titration for isocyanate groups. Using branching theory, viscosity was related to extent of reaction and temperature. Such relations should be useful for process models. Normal force data for the curing system are als

ISSN:0032-3888    

DOI:10.1002/pen.760161205

出版商:Society of Plastics Engineers, Inc.    

年代:1976

数据来源: WILEY

摘要:

AbstractMelt How data has been determined for a series of fractionated and whole low density polyethylenes which has been characterized in terms of their molecular weights and degree of long‐chain branching, (LCB). The resulting data indicate that low LCB influences melt flow both through a reduction in molecular size and an increased level of intermolecular interaction. Die swell measurements on whole polymers indicate an increase in melt elasticity with increase in degree of LCB for samples of similar melt flow (MI). Comparison of GPC data with observed die swell characteristics indicates that die swell is a molecular size dependent property and independent of intermolecular entanglement effects, suggesting that the measurement of elastic properties of LDPE melts will provide a means of determining relative degrees of LCB for commercial resin

ISSN:0032-3888    

DOI:10.1002/pen.760161206

出版商:Society of Plastics Engineers, Inc.    

年代:1976

数据来源: WILEY

摘要:

AbstractIn spite of the availability of‐ almost fifty commercial synthetic plastics, many new ones were announced at the recent First Chemical Congress of the North American. Continent at Mexico City. Among these are the high temperature resistant aramides and imides, poly(phenylene sulfide), poly(phenylene oxide), poly(aryl sulfone), H resin, modified phenolic resins and the phosphazenes. Other new polymers are block and graft copolymers, conductive polymers, barrier resins, poly 1,2‐butadiene, polyolefins and polyurethanes. New coupling techniques and shortages of feed stocks have resulted in a renewed interest in filled plastics and recycled polym

ISSN:0032-3888    

DOI:10.1002/pen.760161207

出版商:Society of Plastics Engineers, Inc.    

年代:1976

数据来源: WILEY

摘要:

AbstractPVC plastisols were formulated with silicone surfactant, mechanically shipped to form froths, and oven‐fused to form open‐cell foams. These were much softer than conventional chemically‐blown foams which contain mixtures of open and closed cells. Increasing plasticizer content and decreasing foam density also had the expected softening effects on foam prope

ISSN:0032-3888    

DOI:10.1002/pen.760161208

出版商:Society of Plastics Engineers, Inc.    

年代:1976

数据来源: WILEY

摘要:

AbstractA recent and joint ACS/SPE symposium featured 40 papers on the fundamental mechanism of brittle fracture, low‐speed crazing and fracture, high‐speed impact mechanisms, fatigue failure, multi‐phase polymer systems, and reinforcing fibers. A survey of these papers indicates the present state of our knowledge in this field, and the rapid progress it is making toward the development of high‐performance plastic ma

ISSN:0032-3888    

DOI:10.1002/pen.760161209

出版商:Society of Plastics Engineers, Inc.    

年代:1976

数据来源: WILEY

摘要:

AbstractA rotating mandrel in a tubing die produces multiaxial orientation in the extruded melt. If the polymer melt is quenched rapidly, some multiaxial orientation is retained in the resultant tubing. Multiaxially oriented tubing exhibits reduced crack propagation and some enhancement of yield and fracture strengths. During the processing of multiaxially oriented tubing, relaxation occurs after the melt leaves the die and gives rise to wall thickening and reduction in the lumen of the tubing; the magnitude of these effects is a function of the rate of mandrel rotation.

ISSN:0032-3888    

DOI:10.1002/pen.760161210

出版商:Society of Plastics Engineers, Inc.    

年代:1976

数据来源: WILEY

摘要:

AbstractPolyphenylene sulfide is a new engineering plastic characterized by a unique combination of useful environmental, mechanical, and flame resistant properties. This paper presents a variety of new developments in molding methods and long term properties of polyphenylene sulfide. Optimum conditions for fabrication by injection molding, compression molding, and free sintering techniques are described along with a comprehensive tabulation of mechanical, factional, and electrical properties of various filled and unfilled compositions. The effect of injection molding conditions and post‐treatments, such as annealing, on mechanical behavior is discussed. Long term stability of molded specimens of the polymer to a variety of chemical environments as well as oven aging studies are reported. The significance of these properties is illustrated by a discussion emphasizing new applications for various compositions based on polyphenylene sulfid

ISSN:0032-3888    

DOI:10.1002/pen.760161211

出版商:Society of Plastics Engineers, Inc.    

年代:1976

数据来源: WILEY