ISSN:0032-3888    

DOI:10.1002/pen.760050413

出版商:Society of Plastics Engineers, Inc.    

年代:1965

数据来源: WILEY

摘要:

AbstractCreep experiments under combined tension and torsion loading are reported for tubular specimens of polyvinyl chloride copolymer. Experiments include a sequence of several combinations of tension and torsion on each specimen with abrupt changes between combinations, including reversal of sense of torsion, recovery and reloading after recovery.Results show a strong path and time dependence for the strain and for the direction of the strain‐rate vector at constant state of stress following a change in state of biaxial stress.The character of the results is described reasonably well by the Boltzmann superposition principle of linear viscoelasticity using a constitutive equation of the form:Examples are given of the use of this equation for common states of stress.Better agreement with the data is obtained from a similar but non‐linear equation employing hyperbolic sine functions of str

ISSN:0032-3888    

DOI:10.1002/pen.760050402

出版商:Society of Plastics Engineers, Inc.    

年代:1965

数据来源: WILEY

摘要:

AbstractThe effectiveness of polyproylene antioxidant systems in other than a simple oxidative environment has been studied. For example, it has been found that contact of stabilized propylene polymers with a number of materials, particularly with plasticized poly (vinyl chloride) and with copper and copper salts, markedly decreases the resistance of the composition toward oxidative degradation. The use of antioxidants having higher molecular weights results in improved retention of stabilization when polypropylene is used in contact with materials such as plasticized poly (vinyl chloride), presumably because partition of the antioxidant from the polypropylene composition is decreased. Antioxidant effectiveness in polypropylene compositions in contact with copper can be greatly increased by the addition of new and more effective copper inbibitors. The usefulness of copper compleming agents such as hydrazides, triazoles, tetrazoles, and derivatives of malonamide and oxamide are compared in polypropylene compositions containing copper dust and antioxidants.

ISSN:0032-3888    

DOI:10.1002/pen.760050403

出版商:Society of Plastics Engineers, Inc.    

年代:1965

数据来源: WILEY

摘要:

AbstractProteins and synthetic polypeptides undergo specific catalytic cleavage by enzymes. It is the object of this article to review the specific hydrolytic, redox, and electron transfer reactions involving enzymes and their mechanisms. The stability of the synthetic high polymers in the biochemical environments is much higher than that of proteins in general, but the increasing use of these materials in the field of surgical implants and internal prostheses has necessitated the systematic long range study of the systems in these surroundings. The enzymatic attack on the synthetic polymers has not been the subject of general study until now, but the intimate knowledge of the specificity and mode of attack of the enzymes, in case of the proteins, would pave the way towards experimental designs to elucidate the comparative stability of various synthetic plastics in these environments. The study of the correlation of the mechanical strength and the chemical structures of these polymers tested as implants in living animals is reviewed, and the suitability of several synthetic polymers for this application is discussed.

ISSN:0032-3888    

DOI:10.1002/pen.760050404

出版商:Society of Plastics Engineers, Inc.    

年代:1965

数据来源: WILEY

摘要:

AbstractCommon methods of calculating screw characteristics are reviewed, and predictions of performance based on these techniques are compared with those based upon the exact solution for simultaneous pressure and drag flow in a plane infinite slit. The error made in superimposing pressure and drag flow, as if each were independent of the other, is indicated. Some brief remarks are also made with regard to the effect of transverse (cross‐channel) flow on the output of the extrude

ISSN:0032-3888    

DOI:10.1002/pen.760050405

出版商:Society of Plastics Engineers, Inc.    

年代:1965

数据来源: WILEY

摘要:

AbstractThe flow of high‐density polyethylene at high shear rates in round dies in laboratory instruments and in extruders depends in an unusual way on capillary diameter. With small diameters this dependence can be explained in terms of slippage of the melt at the wall of the capillary; with large diameters, in terms of temperature increases developed through viscous flow. A rapid increase in slip velocity appears to be responsible for a discontinuity in the flow curve determined in laboratory instruments. Recurring transitions between the two branches of the flow curve are responsible for the oscillating flow observed in equipment operating at constant or nearly constant throughput rate. The energy stroage capability of the over‐all system, apparatus plus melt, controls the dynamic aspects of flow in the vicinity of the discontinu

ISSN:0032-3888    

DOI:10.1002/pen.760050406

出版商:Society of Plastics Engineers, Inc.    

年代:1965

数据来源: WILEY

摘要:

AbstractStudies of polypropylene oxyluminescence show the luminous intensity to be dependent upon the degre of oxidation. The length of the low intensity level portion of the luninescence curve, or pseudo induction period, was found to be a measure of the useful stabilizer life, and the intensity of this portion indicative of the effectiveness of stabilization. The effect of peroxide decomposers was studied and results indicate that peroxide reactions are major producers of luminescence. Analysis of the accepted modes of polymer oxidation, in view of our luminescence findings, indicate that the rate of luminescence buildup should depend upon ease of R. formation and the luminous intensity should be dependent on peroxy radical concentration. The effect of tertiary‐carbon content on luminescence was also investigated, and luminous intensity was found to be dependent upon the amount of polymer branching. Model Compounds having slight structural variations were examined and were found to produce different intensity‐time curves during oxidation, which may be attributed to ease of formation of a reactive site and subsequent peroxy radical reacti

ISSN:0032-3888    

DOI:10.1002/pen.760050407

出版商:Society of Plastics Engineers, Inc.    

年代:1965

数据来源: WILEY

摘要:

AbstractThis article describes the experimental investigations on fracture of a polymeric material under various uniaxial and biaxial stress fields, at controlled rates of loading. The biaxial stress fields have been produced by subjecting tubular specimens to pure internal pressure, internal pressure combined with tension loading, pure torsion and torsion combined with tension loadings. The experimental arrangements developed for conducting the above tests have been described. Examination of fractured specimen subjected to various biaxial stress fields indicates that the fractured surface is mostly along the plane of maximum normal stress. However, the mode of fracture in the case of pure compression test resembles that of a brittle material. From the experimental fracture data, limiting failure curves for the material have been obtained corresponding to various maximum extension ratio rates. The experimental failure data were compared with various criteria of failure essentially developed for metals. It was found that none of the classical failure criteria applies to the material tested.

ISSN:0032-3888    

DOI:10.1002/pen.760050408

出版商:Society of Plastics Engineers, Inc.    

年代:1965

数据来源: WILEY

摘要:

AbstractSixteen polymers containing thiazole and aromatic rings in the polymer chain were prepared and investigated for the production of fibers and films that would be useful up to about 500°C. None of these polymers was completely satisfactory. Some of the polymers gave tough fibers and films, but they had relatively low melting points (<300°C). Other polymers did not melt below 500°C, but they did not have good fiber and film forming properties because of their low molecular weights. Fibers and films of one of the polymers (polytetramethylenephenylenethiazole) were prepared, and their physical properties, hydrolytic stabilites under acid and alkaline conditions, and resistence to ultraviolet and gamma radiations were determin

ISSN:0032-3888    

DOI:10.1002/pen.760050409

出版商:Society of Plastics Engineers, Inc.    

年代:1965

数据来源: WILEY

摘要:

AbstractThe effect of various environmental conditions, other than chemical, on the mechanical properties of amorphous polymers is considered. The response of such polymers to an applied stress or strain depends on the mobility of polymeric chains which in turn is largely a function of free volume. The free volume varies with temperature, pressure, and plasticizer concentration; in the glassy state, it also depends on thermal history and tensile strain. These concepts are reviewed and some illustrative data, primarily from the published literature, are presented. A discussion is also given of the nonlinear viscoelastic properties (in uniaxial tension) of amorphous network polymers in the rubbery state. Methods for characterizing the ultimate tensile properties of such polymers are also described. Finally, some comments are made about the mechnical characteristics of polymers in the glassy state.

ISSN:0032-3888    

DOI:10.1002/pen.760050410

出版商:Society of Plastics Engineers, Inc.    

年代:1965

数据来源: WILEY