摘要:

AbstractDeformation during cooling and take‐up of rectangular, triangular and T‐shaped profiles were investigated. Experimental results show that there is an excellent agreement between changes in a cross‐section dimension and prediction from the theory for various take‐up speeds. The correlations decrease in the case where other process variables such as different melt temperatures and output rates are involved. Based on undrawn sample measurements, it has been concluded that to a high degree of approximation only a scaled‐down change in shape occurs along the drawing path after die swell is completed. Industrial practices in handling profiles during cooling and take‐up which may cause deviations from geometrically similar deformation were examined. Metal guides and local cooling by small water streams along the drawing path were used to impose shear forces on the profile. It was found that the effects of such shear forces has been small in comparison with the effects of elongational stress as indicated by only slight, if any, deviation from geometrically similar changes in cross‐sections. Based on the data obtained, it is concluded that feedback control during profile drawing to give correct size is feasible based on monitoring a single dimension. The correct shape can, however, be obtained only by choice of the proper die geometry and other extrusi

ISSN:0032-3888    

DOI:10.1002/pen.760201802

出版商:Society of Plastics Engineers, Inc.    

年代:1980

数据来源: WILEY

摘要:

Abstractβ′‐relaxation temperatures (Tβ′) provide a sensitive measure of the relative efficiencies of plasticizers in altering such properties of cellulose ester plastics as their impact strength, melt‐How, and modulus. Anomalies may occur, however, if the plasticizer‐compatibility limit in the polymer is surpassed. In addition, different correlations ofTβ′and polymer properties are observed for liquid and soli

ISSN:0032-3888    

DOI:10.1002/pen.760201803

出版商:Society of Plastics Engineers, Inc.    

年代:1980

数据来源: WILEY

摘要:

AbstractReaction injection molding (RIM) elastomers are being seriously considered by major automotive companies as a substitute for metal in exterior body panels. One major consideration in this application is dimensional stability at a 325°F paint bake cycle. Reported here are formulations which via novel processing result in finished parts with excellent dimensional stability at 325°F. In addition, other properties such as impact resistance and flex modulus ratio improve parallel with high temperature performance. Mechanical properties as a function of processing and molding parameters are presented. Other studies are presented and a tentative explanation of the superior performance of these RIM elastomers is mad

ISSN:0032-3888    

DOI:10.1002/pen.760201804

出版商:Society of Plastics Engineers, Inc.    

年代:1980

数据来源: WILEY

摘要:

AbstractInitiation of chemical reactions by ultra‐violet light is characterized by essentially complete lack of temperature dependence and by physical separation of the source or initiating agent from the reaction medium. The advantage of these features for reactor stability and control are discussed in a theoretical study of the photo‐sensitized polymerization of styrene in a continuous stirred tank reactor and a comparison is made with the behavior of the thermally initiated react

ISSN:0032-3888    

DOI:10.1002/pen.760201805

出版商:Society of Plastics Engineers, Inc.    

年代:1980

数据来源: WILEY

摘要:

AbstractDynamic mechanical measurements have become increasingly more common as an interpretative tool for identifying structure‐property relationships in polymers, especially in multi‐phase systems. There are many literature references citing the application of this analytical technique to the study of rubber reinforced polymers such as high impact polystyrene and aerylonitrile‐butadiene‐ styrene. This paper illustrates further extensions of the technique to study the effects of composition and processing parameters on the mechanical relaxation behavior of rubber reinforced high nitrile resins. Storage and loss curves vs temperature are compared for three related polymer systems: (1) a high nitrile glassy copolymer, (2) mechanical blends of the glassy copolymer with rubber, and (3) a copolymer grafted onto a rubber backbone. Particular attention is given to the size and shape of the tan δ loss peak for blended and grafted resins having different rubber levels. The importance of dispersing the rubber particles during processing is also shown. Dynamic mechanical studies have shown a pronounced decrease in the size of the rubber loss peak for oriented rubber modified high nitrile resins. This is further evidence that dynamic mechanical results are sensitive to variations in processing conditions as well as resin com

ISSN:0032-3888    

DOI:10.1002/pen.760201806

出版商:Society of Plastics Engineers, Inc.    

年代:1980

数据来源: WILEY

摘要:

AbstractThe effect of cold rolling on impact strength of poly(vinyl chloride) (PVC) acrylonitrile‐butadiene‐styrene (ABS), and an alloy of ABS and polycarbonate (Cycoloy) was studied. The results were presented in terms of Izod impact strength and present oil thickness reduction. The residual stresses molecule orientation and modification of mechanical properties due cold rolling were measured. It was shown that the mechanism of toughness enhancement in PVC, ABS, and Cycoloy different than the one observed in rolled polycarbonates. In the case of a highly localized failure initiation event (a single eraxe), which appears to be present in polycarbonate, the influence of residual stresses, is great, whereas in rubber modified polymers having multiple erasing over a large volume, orientation is more important than residual stress. Hot rolling of poly(methyl methaerylate) holds promise for a continuous process to achieve orientation and toughness enhancem

ISSN:0032-3888    

DOI:10.1002/pen.760201807

出版商:Society of Plastics Engineers, Inc.    

年代:1980

数据来源: WILEY

摘要:

AbstractA mathematical model is derived for isothermal flow of a Newtonian liquid through corotating twin screw equipment. Two different flow regimes are studied. In the first, channels of twin screw equipment are completely filled with liquid, generate a pressure gradient, and provide a discharge pressure at the end of the pump. Equations are given for drag flow rate, pressure backflow rate, and flow rate through the nip zone. It is shown how the analysis of single screw pumps can be modified for twin‐screw pumps. In the second regime channels are partly full, which is the case with extraction equipment. Equations show how the degree of fill in the equipment changes with flow rate, speed, and dimension

ISSN:0032-3888    

DOI:10.1002/pen.760201808

出版商:Society of Plastics Engineers, Inc.    

年代:1980

数据来源: WILEY

摘要:

AbstractThe application of die‐drawing to the production of highly oriented polymers is considered, ft is shown that a variety of useful products can be obtained including not only rod and multifilament, but also tube and filled polymer. The investigations under discussion include the processing of several grades of linear polyethylene, polypropylene homopolymer and co‐polymer. In favorable cases, products of very high stiffness were obtained, reaching modulus values of 50 GPa for linear polyethylene and 20 GPa for polypropyl

ISSN:0032-3888    

DOI:10.1002/pen.760201809

出版商:Society of Plastics Engineers, Inc.    

年代:1980

数据来源: WILEY

摘要:

AbstractThe degradation rates of free radical polymerized and syn‐diotactic poly(methyl methacrylate) (PMMA) under electron radiation were explored at temperatures ranging from 225 to 325°C and at electron dose rates from 10,000 rads/min to 100,000 rads/min. Scission of bonds between main‐chain atoms resulted in pairs of radical chain ends, of which some disportionated, thereby reducing polymer molecular weight without loss of volatile, while others proceeded to depropagate via the usual radical transfer, causing complete volatilization of the chain without significant change of molecular weight of the residual polymer. Electron irradiation at a dose rate of 100,000 rads/min produced a significant enhancement in the reaction, rate, and reduced the overall activation energy from 140 KJ/g‐mole observed for thermally induced depropagation to a value of 75 KJ/g‐mole observed during simultaneous irradiation and/thermal depro

ISSN:0032-3888    

DOI:10.1002/pen.760201810

出版商:Society of Plastics Engineers, Inc.    

年代:1980

数据来源: WILEY

ISSN:0032-3888    

DOI:10.1002/pen.760201801

出版商:Society of Plastics Engineers, Inc.    

年代:1980

数据来源: WILEY