摘要:

AbstractPrevious work has shown evidence that PMMA and PEMA are miscible with PVF2. The present paper examines in detail the behavior of PEMA/PVF2blends by thermal analysis and dynamic mechanical testing. All transitions and relaxations are affected by blond composition but in a complex manner owing to the crystallization of PVF2from blends rich in this component. Inadequacies of the simple two‐phase picture of semi‐crystalline polymers is believed responsible for some of the transitional behavior observed here. The melting point depression observed for PVF2was found to be consistent with an exothermic heat of mixing for this pair comparable in value to that found for PPMA/PVF2/All evidence here are consistent with the previous conclusion of miscibility for these syst

ISSN:0032-3888    

DOI:10.1002/pen.760160902

出版商:Society of Plastics Engineers, Inc.    

年代:1976

数据来源: WILEY

摘要:

AbstractExperiments are described which show that stresses in amorphous polymers can be measured by diffracting X‐rays at high Bragg angles from a filler consisting of crystalline particle or powders. The method is applicable, when calibrated, to both applied and residual stresses, to stress relaxation studies, to both tensile and compressive stresses, to both interior and surface positions in an object, and to composites of various types as well as to polymers that are substantially homogeneous. In the lower (Hookian) range, strains and stresses in metallic embedded particles increase linearly with applied stresses and strains in the matrix. When applied stresses exceed an apparent yield point, which correlates with the yield strength of the metallic filler, the elastic strains in the particles increase only slightly or even decrease as the matrix strains are increased, and with constant applied strain, the particles reveal changes due to relaxation. Strains in the particles are found to be smaller, and stresses higher, than in the matrix. Tests of graphite‐fiber epoxy composites with embedded filings of silver or aluminum alloy show that compressive residual stresses from curing at 350°C and cooling to room temperature are registered in the particles as well as stresses externally applied to the cured composite. Precision of the order of 1000 psi (0.7 kg/mm2or 6.9 M Pa) was obtained with measurements made and evaluated rapidly and simply; with more refined techniques, much higher precision would be poss

ISSN:0032-3888    

DOI:10.1002/pen.760160903

出版商:Society of Plastics Engineers, Inc.    

年代:1976

数据来源: WILEY

摘要:

AbstractCharacteristics of the fracture of fiber reinforced plastic composites are described in terms of the elastic stress distribution at the crack tip, the mechanism of crack tip damage, and the modes and conditions of final fracture. The three‐dimensional, stress field at the tip of a sharp crack in a laminate is presented and contrasted to traditional two‐dimensional models. The response of the material in the form of inter‐ and intraply damage formation and growth under increasing load is characterized, and its effect in blunting the main crack is examined. The final fracture conditions, which may range from quasi‐brittle to notch insensitive, are discussed and related to the damage zone extension. Observed and anticipated effects of various material and geometric parameters are also di

ISSN:0032-3888    

DOI:10.1002/pen.760160904

出版商:Society of Plastics Engineers, Inc.    

年代:1976

数据来源: WILEY

摘要:

AbstractThe thermal conductivity of a solid or gas filled polymer is used in processing or end use application calculations. Numerous theoretical and empirical correlations are found in the literature. A careful review of these models indictes that no one correlation or technique accurately predicts the thermal conductivity of all types of composites. The investigation indicated that for solid filled composites the Lewis and Nielsen equation fitted the experimental data best for the range of fillers tested. However, for a gas filled polymer, none of the theoretical models proved adequate. The semi‐empirical approach of Harding showed considerable meri

ISSN:0032-3888    

DOI:10.1002/pen.760160905

出版商:Society of Plastics Engineers, Inc.    

年代:1976

数据来源: WILEY

摘要:

AbstractAn extensive set of rheological data, including steady shear, normal stress, and oscillatory response functions, have been obtained for several polyethylene melts, and a modified form of the Spriggs nonlinear co‐rotational model has been used to represent the data. The resulting model was used to predict the transient stress response of the melts in a simplified model of the extrusion process, with a resulting criterion for the onset of melt distortion in terms of readily evaluated rheological parameters. The predicted occurrence of melt distortion based on this criterion agreed well with observations for the polymers in this study as well as for a variety of other polymers reported in the literatur

ISSN:0032-3888    

DOI:10.1002/pen.760160906

出版商:Society of Plastics Engineers, Inc.    

年代:1976

数据来源: WILEY

摘要:

AbstractThis report describes the influence, of (a) degree of biaxial orientation, (b) stretching rate, and (c) stretching temperature on the tensile, dynamic mechanical and dielectric properties of non‐impact modified PVC. A new parameter designated “planar strain” is used to correlate anisotropic property values with both equal and unequal biaxial stretching in a single two‐dimensional plot, thereby providing a direct comparison of the effects of two or more biaxial stretching ratios. It is shown that optimum stretching conditions depend to some extent upon end use and that a 2 × 2 stretch ratio is optimum for impact resistance. The actual property/processing condition relationships exhibit very complicated interactions and are correlated empirically in this study. The dynamic measurements suggest that overall local segmental beta motion is increased after orientation but that the relative chain alignment makes it more difficult to activate thi

ISSN:0032-3888    

DOI:10.1002/pen.760160907

出版商:Society of Plastics Engineers, Inc.    

年代:1976

数据来源: WILEY

摘要:

AbstractA detailed study of the fracture behavior of polyarylsulfone was conducted over a temperature range of −175 to 120°C. Both fatigue crack propagation and fracture toughness tests were run as well as forced torsion pendulum tests to characterize the dynamic properties. The polymer exhibited a broad secondary loss peak and a high glass transition temperature at −110 and 295°C, respectively. Fracture toughness,KIC, and fatigue crack growth resistance were found to vary similarly with temperature, minima being observed near −50°C. Below that temperature, both a rise in toughness and in fatigue resistance is associated with the broad secondary loss peak. The slopes of the log fatigue crack velocity (da/dN) vs log stress intensity range (ΔK) curves varied from 2.6 to 13.2. Since the equation da/dN= α(ΔK)ndescribed all of the data, the log‐log slope or exponent,n= ∂ln(da/dN)∂ln ΔK, was considered as a stress intensity sensitivity index with respect to fatigue behavior. This index was at a maximum near −50°C, where the minimum in toughness occurred. A kinetic model was utilized to correlate the stress intensity sensitivity index and suggested that a single thermally activated mechanism controls the low temperature mechanical behavi

ISSN:0032-3888    

DOI:10.1002/pen.760160908

出版商:Society of Plastics Engineers, Inc.    

年代:1976

数据来源: WILEY

摘要:

AbstractQuantitative Differential, Thermal Analysis has been used in the wire and cable industry for determining the degree of oxidative stability of polyolefins for quality control purposes in lieu of a direct antioxidant analysis, However, it has never been shown whether the presence of each additive in a stabilizer package could be detected by this method. The results presented here indicate that the presence of a primary antioxidant and a copper inhibitor in combination can be detected separately by comparing the oxidative induction times in copper and aluminum pans. The addition of a thioester synergist such as distearyl thiodipropionate, DSTDP, is evidenced by an increased induction time in aluminum pans. However, the presence of DSTDP makes it impossible by this method to determine whether an effective level of copper inhibitor is present since the sample shows a reduced stability on copper compared to aluminum. One of two factors can be invoked to explain these results: a) DSTDP interferes with the complexing ability of the copper inhibitor or b) the copper‐inhibitor complex retards the synergistic effect of the DSTDP. In either case, this factor is not important at lower temperatures since oxygen uptake data at 130°C indicate that DSTDP is an effective synergist in the presence of copp

ISSN:0032-3888    

DOI:10.1002/pen.760160909

出版商:Society of Plastics Engineers, Inc.    

年代:1976

数据来源: WILEY

ISSN:0032-3888    

DOI:10.1002/pen.760160901

出版商:Society of Plastics Engineers, Inc.    

年代:1976

数据来源: WILEY