摘要:

AbstractUnless suitably stabilized and coated, fiber‐reinforced composites are subject to photoinitiated oxidation which results in a degradation of the resin surface and an eventual reduction in the composite's mechanical properties. The photo‐oxidation, which is initiated by UV‐absorbing oxidation products created during cure, is relatively amenable to detection by techniques of analytical chemistry. Mechanical test results, which reflect a wide range of material properties, are more subject to variability and misinterpret

ISSN:0032-3888    

DOI:10.1002/pen.760180402

出版商:Society of Plastics Engineers, Inc.    

年代:1978

数据来源: WILEY

摘要:

AbstractThe effect of cold rolling and subsequent annealing on the anisotropy of tensile properties has been studied by annealing 33 percent cold rolled polyoxymethylene at 70, 120 and 170°C and measuring the properties at 0, 45 and 90° from the rolling direction. The mechanical and thermal treatments exhibit a significant effect on the directional nature of the properties. The changes in mechanical properties have been accounted for in terms of the changes in morphology, fracture behavior and orientation as studied by a differential thermal analyzer, electron microscopy and wide‐angle X‐ray diffra

ISSN:0032-3888    

DOI:10.1002/pen.760180403

出版商:Society of Plastics Engineers, Inc.    

年代:1978

数据来源: WILEY

摘要:

AbstractWe consider the connection between viscous effects experienced by polytetrafluoroethylene paste during extrusion, and the final strength of the extrudate. It is shown that by reducing the viscous contribution to the pressure drop across the extruder die, we not only save on extrusion pressure, but also increase the strength of the extrudate. The shape of die that gives the minimum pressure drop is derived.

ISSN:0032-3888    

DOI:10.1002/pen.760180404

出版商:Society of Plastics Engineers, Inc.    

年代:1978

数据来源: WILEY

摘要:

AbstractA study has been made on the impact and yield properties of polycarbonates from two manufacturers as a function of strain rate, melt flow rate, notch radius, thermal history, and test temperature. The yield stress increases with the strain rate and annealing time in exactly the way predicted by a recently proposed theory on nonlinear viscoelasticity of glassy polymers. The critical molecular weight for the transition from a ductile to a brittle break increased at higher rate of strain and also with the longer annealing times.

ISSN:0032-3888    

DOI:10.1002/pen.760180405

出版商:Society of Plastics Engineers, Inc.    

年代:1978

数据来源: WILEY

摘要:

AbstractA basic study is reported of extrusion and injection molding for melts of polyethylene and polystyrene filled with glass fibers. It is shown that glass fibers cause large increases in end pressure losses and decreases in extrudate swell. Flow visualization of injection molding studies indicates that polymer melts containing high loadings of glass fibers exhibit jetting in end gated molds. This is attributed to the reduction in extrudate swell. To avoid jetting, special care is required in design of gating.

ISSN:0032-3888    

DOI:10.1002/pen.760180406

出版商:Society of Plastics Engineers, Inc.    

年代:1978

数据来源: WILEY

摘要:

AbstractOrientation development in amorphous polymer melts being vitrified in an injection molding process is described. Predictions of orientation development are based on the argument that the stress‐optical laws are valid in the molten stare and birefringence values appropriate to the stress levels at the time of vitrification remain. This theory is compared to birefringence distributions determined in injection molded part

ISSN:0032-3888    

DOI:10.1002/pen.760180407

出版商:Society of Plastics Engineers, Inc.    

年代:1978

数据来源: WILEY

摘要:

AbstractFlow curves were obtained at 190°C over the shear rate range 0.1 to 100 sec−1for polystyrene‐acrylonitrile copolymer containing up to 36 percent by volume glass beads, using a capillary extrusion rheometer. The addition of glass beads always increased shear stress and viscosity at a given shear rate, with the increase being more pronounced at low shear rates. The addition of glass beads decreased die swell, which also depended on shear‐stress and capillary length‐to‐radius ratio. At low shear rates a lower limiting value of die swell ratio of about 1.1 was achieved. Values of recoverable shear derived from end correction data by the technique of Philippoff and Gaskins and from die‐swell data by the method of Bagley and Duffey are compared. A fairly good agreement was found for low concentration blends at low shear, However, the values differed by a factor of up to 3 at higher shear stresses. In all cases, recoverable shear was found to increase with shear stress at a fixed filler loading and to decrease with increased filler loading at a fixed shear stress. Values of shear modulus calculated from the recoverable shear measurements decreased rapidly with increasing

ISSN:0032-3888    

DOI:10.1002/pen.760180408

出版商:Society of Plastics Engineers, Inc.    

年代:1978

数据来源: WILEY

摘要:

AbstractTemperature distribution at the exit of the leakage gap is of interest for a number of problems. For the calculation of temperatures, the leakage flow may be considered to be a pure drag flow to a good approximation. In the Newtonian case, thermal development length may be expressed in terms of gap height as L ≈ 3/8Pe· δ;usually this is less than the available gap length.Peis the Peclet number and δ the height of leakage gap. Therefore the existing flow may be considered fully developed. For power law fluids, numerical calculations lead to results of the same order. Martin's results therefore may be applied to the flow at the exit of the leakage

ISSN:0032-3888    

DOI:10.1002/pen.760180409

出版商:Society of Plastics Engineers, Inc.    

年代:1978

数据来源: WILEY

摘要:

AbstractIn this paper the effect of temperature and filler content ϕ on electrical resistivity of styrene‐acrylonitrile polymer filled with iron or aluminium powders has been investigated. The resistivity of such composites decreases suddenly by several orders of magnitude at a critical volume concentration ϕc, which depends on the size distribution of particles and on thermal history. For filler content lower than ϕc, the resistivity decreases with increasing temperature, whereas for ϕ>ϕcthere is a sudden increase in resistivity at temperatures near the glass transition temperature of the polymeric matrix. This effect is more pronounced than the previously reported data on other composite s

ISSN:0032-3888    

DOI:10.1002/pen.760180410

出版商:Society of Plastics Engineers, Inc.    

年代:1978

数据来源: WILEY

摘要:

AbstractOne of the problems to be considered in the application of the Halpin‐Kardos theory to crystalline polymers is the relation of the crystal length to the only related and measurable parameter, spherulite size. The number average crystal length has been computed for various two and three dimensional models for the crystallization process assuming heterogeneous nucleation. It was found that high values of crystallinity are consistent only with lamellae that are stacked in a parallel fashion. For these systems the number average lamellar length is 0.55 of the spherulite radius. Lower crystallinity polymers have an average lamellar length 0.3 to 0.5 of the spherulite radius, the actual value being determined by the radius. For spherulites of radius 1μm or greater, the size of the primary nucleus has no noticeable influence on the average lamellar leng

ISSN:0032-3888    

DOI:10.1002/pen.760180411

出版商:Society of Plastics Engineers, Inc.    

年代:1978

数据来源: WILEY