摘要:

AbstractFollowing the discovery that linear polyethylene can be drawn to very high draw ratios to produce oriented fibres and films with ultra‐high initial moduli, a similar study has been undertaken for polypropylene. In particular, the modulus/draw ratio relationship has been obtained for a range of polymers of different molecular weight and molecular weight distribution. The effects of thermal history and draw temperature were studied, and it was shown that under optimum conditions material with an initial modulus at room temperature of 1.9 × 1010Nm−2(205 gdtex, 3 × 106psi) can be obtained. This value is at least 50 percent greater than those previously recorded for drawn fibres and about one half of the theoretical mo

ISSN:0032-3888    

DOI:10.1002/pen.760161102

出版商:Society of Plastics Engineers, Inc.    

年代:1976

数据来源: WILEY

摘要:

AbstractLinear crystalline polymers can be processed to high degrees of orientation sufficient to produce dramatic increases in tensile strength and modulus. Three processes have been identified for inducing such orientation: cold drawing, hydrostatic extrusion, and solution spinning. All three processes utilize a high elongational velocity gradient in a critical temperature range to produce a high strength crystalline morphology. Although the molecular superstructure may differ in each case, the mechanical properties are similar, An increase in strength is achieved either through the creation of new tie molecules between crystal lamellae or through the creation of an extended chain crystal substructure. Temperature and molecular weight are the prime variables in determining which morphology will develop. The optimum processing temperature for many of the specific techniques is the crystalline dispersion temperature. At this temperature, the crystal structure is particularly adaptable to forming a new crystal morphology. Ul‐tradrawn polymers are more Hookean in behavior than isotropic polymers and have properties similar to steel and glass. Polyoxymethylene has been processed most closely to its theoretical strength. Polyethylene, which is the most difficult to process, has achieved the highest modulus of any common polyolefin polymer, about 7 × 1010

ISSN:0032-3888    

DOI:10.1002/pen.760161103

出版商:Society of Plastics Engineers, Inc.    

年代:1976

数据来源: WILEY

ISSN:0032-3888    

DOI:10.1002/pen.760161104

出版商:Society of Plastics Engineers, Inc.    

年代:1976

数据来源: WILEY

摘要:

AbstractAlmost all polymer processing operations involve moving and shaping the polymer as a melt and then cooling it, usually quite rapidly, to a solid state. In order to develop models for such processes we have begun systematic studies in non‐isothermal rheology; here we interpret the results in the context of melt spinning. Theoretical predictions of stress vs distance from the spinneret were calculated from generalized (non‐isothermal) viscoelastic theory and compared with Dees' melt spinning data on high density polyethylene. Despite certain experimental and theoretical difficulties, the agreement is good. Surprisingly, an additional theoretical curve, based on a simple Trouton viscosity, also gave a reasonable approximation over much of the distance, despite the transient nature of the flow. To understand this phenomenon further, a more tractable theoretical problem was studied in detail; the problem, of constant elongational flow (Ė= constant) in the presence of a constant rate of temperature change (dT/dt= constant). The results depend on two dimensionless groupings; the first is the usual product of a relaxation time andĖ; the second involves the ratio of normalized dT/dttoĖ. When the second group is large, a quasi‐viscous state exists. The melt spinning data for the HDPE may be near th

ISSN:0032-3888    

DOI:10.1002/pen.760161105

出版商:Society of Plastics Engineers, Inc.    

年代:1976

数据来源: WILEY

摘要:

AbstractMold flows and melt viscosities of an incompatible bi‐component EPDM and “Viton” fluoroelastormer system were examined. A marked reduction in the melt viscosities of either component was observed when a small amount of the other component was present. It was speculated that the phenomenon was a result of a slippage between the polymer and the coated capillary surface due to the presence of a minor amount of the incompatible polymer. Evidence is given to indicate that this effect cannot be accounted for using the “melt structural heterogeneity” mechanism proposed for a different system by An

ISSN:0032-3888    

DOI:10.1002/pen.760161106

出版商:Society of Plastics Engineers, Inc.    

年代:1976

数据来源: WILEY

摘要:

AbstractA new technique for improving the strength of bonded joints between various materials and different adhesives is described. Increased strength was obtained by mechanical Surface Activation Beneath Reactive Adhesives (SABRA). This technique results in higher bond energies due to the creation of free radicals. The surfaces were activated by abrasion with emery paper in the presence of the adhesive itself (epoxy), or of some suitable primer such as methyl methacrylate, acrylonitrile (AN) or hydrogen sulfide gas. The effects of this technique were demonstrated by four different methods: 1) Improved wetting of standard epoxy or water drops on the treated surface. 2) Achievement of bond energies between primers and polymeric surfaces exceeding the energy of solution in solvents, which were revealed by attenuated total reflectance infrared. 3) The detection of free radicals created by bond scission during abrasion by means of diphenylpicryl hydrazyl, (DPPH), a free radical scavenger, monitored by spec‐trocolorimetry, 4) Destructive testing of single lap joint test Pieces, scarfed tube joints and pee) test samples. These experiments will be described in a second paper. The theoretical base of the new approach is supported by a tentative estimate of energies set free by mechanochemical creation of free radicals and the excess heat released during abrasio

ISSN:0032-3888    

DOI:10.1002/pen.760161107

出版商:Society of Plastics Engineers, Inc.    

年代:1976

数据来源: WILEY

摘要:

AbstractThe Part I paper described the mechanochemical basis for achieving high adhesive strength in bonds between polymeric surfaces such as polyethylene, polypropylene, and Teflon, using the SABRA method (Surface Activation Beneath Reactive Adhesives). This paper gives a brief survey of bonding techniques as well as results of shear tests of simple lap joints and scarfed tube joints. They compared favorably with other methods such as CASING, Peeling test results are also presented. Mixed systems were examined such as glass fiber reinforced polyester bonded to polypropylene and aluminum with thin films of polymeric material sandwiched between. A start was made towards of optimization and exploration of primer specificity for different materials, The implications and further applications of the SABRA method are discussed.

ISSN:0032-3888    

DOI:10.1002/pen.760161108

出版商:Society of Plastics Engineers, Inc.    

年代:1976

数据来源: WILEY

摘要:

AbstractVarious blends over extended compositional ranges have beer, prepared for combinations of a thermoplastic urethane elastomer with polystyrene, a styrene‐acrylonitrile copolymer, a polyhydroxyether (Phenoxy A), and poly(vinyl ethyl ether). The thermoplastic urethane elastomer was based on a polycaprolactone diol of approximately 2100 number average molecular weight, 4,4′‐diphenylmethane diisocyanate and 1,4‐butanediol at a molar ratio of 1/2/1, respectively. At ambient temperature, the tensile properties of the blends typically are intermediate between the values of the two separate components. Characterizations of the dynamic mechanical properties of the blends show the relative degree of compatibility for the thermoplastic urethane elastomer and the respective polymers. Two separate glass transitions are obtained for blends of polystyrene and the styrene‐acrylonitrile copolymer with the thermoplastic urethane elastomer. This behavior demonstrates that these blend systems are incompatible. The blends of Phenoxy A and the thermoplastic urethane elastomer exhibit a single glass transition for which the temperature is dependent on the respective concentration of the components. These mixtures are considered to be compatible

ISSN:0032-3888    

DOI:10.1002/pen.760161109

出版商:Society of Plastics Engineers, Inc.    

年代:1976

数据来源: WILEY

摘要:

AbstractThe stress‐strain behavior of a material exhibiting Andrade creep (for which the creep compliance is linear in the cube‐root of time) has been calculated for loading at constant strain rate\documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\rm \varepsilon}\limits^{\rm .} $\end{document}and at constant stress rate\documentclass{article}\pagestyle{empty}\begin{document}$ \mathop \sigma \limits^. $\end{document}for the limiting case of linear viscoelastic behavior and at constant\documentclass{article}\pagestyle{empty}\begin{document}$ \mathop \sigma \limits^. $\end{document}for one type of nonlinear viscoelastic response. The recoverable strain after the stress has been removed has also been calculated for these three cases. The results of the calculations are compared with experim

ISSN:0032-3888    

DOI:10.1002/pen.760161110

出版商:Society of Plastics Engineers, Inc.    

年代:1976

数据来源: WILEY

ISSN:0032-3888    

DOI:10.1002/pen.760161101

出版商:Society of Plastics Engineers, Inc.    

年代:1976

数据来源: WILEY