摘要:

AbstractThe free volume, vf, of liquids is defined in many ways. Comparison of solid and liquid behavior indicates that the definition for free volume in terms of the internal pressure of the liquid (∂E/∂V)T, is physically reasonable. Application of the definition of free volume, vf=RT/(∂E/∂V)T, to polymethylenes, coupled with surface energy values, leads to an evaluation of both polymer segmental volume, Ṽs, and free volume per segment, (vf)s, as a function of temperature. These equilibrium thermodynamic measurements of Ṽsand (vf)slead to an energy of activation for viscous flow in good agreement with viscosity studies. Information of this type could be of great use in considering many current problems in polymer flow such as the effect of pressure o

ISSN:0032-3888    

DOI:10.1002/pen.760110302

出版商:Society of Plastics Engineers, Inc.    

年代:1971

数据来源: WILEY

摘要:

AbstractPoly(vinyl chloride) was fractionated and its solution properties were studied. Calibration of the gel permeation chromatograph was carried out using poly(vinyl chloride) and polystyrene. Empirical correlations were established for the calibration plots.

ISSN:0032-3888    

DOI:10.1002/pen.760110303

出版商:Society of Plastics Engineers, Inc.    

年代:1971

数据来源: WILEY

摘要:

AbstractA new gel permeation chromatography (GPC) method is proposed for determining the unperturbed end‐to‐end distance,\documentclass{article}\pagestyle{empty}\begin{document}$ \left({\frac{{r_0 ^2 }}{M}} \right)^{0.5} $\end{document}, of polymers of known molecular weights,MnandMw. This method requires the value of\documentclass{article}\pagestyle{empty}\begin{document}$ \left({\frac{{r_0 ^2 }}{M}} \right)^{0.5} _{{\rm ps}} $\end{document}of polystyrene which was determined through viscometry to be 0.735\documentclass{article}\pagestyle{empty}\begin{document}$ \left({\frac{{{\rm {\AA}}^2-{\rm mole}}}{{gm}}} \right)^{0.5} $\end{document}Polyvinyl chloride (PVC) was chosen to illustrate the method and\documentclass{article}\pagestyle{empty}\begin{document}$ \left({\frac{{r_0 ^2}}{M}} \right)^{0.5} _{pvc} $\end{document}was found to be 0.99 from GPC data which is in agreement with the result obtained from viscometry,\documentclass{article}\pagestyle{empty}\begin{document}$ \left({\frac{{r_0 ^2}}{M}} \right)^{0.5} _{pvc} $\end{document}= 1.01. All\documentclass{article}\pagestyle{empty}\begin{document}$ \left({\frac{{r_0 ^2 }}{M}} \right)^{0.5} $\end{document}values were determined at 30°C. The advantage to this method lies in its speed and economy of mater

ISSN:0032-3888    

DOI:10.1002/pen.760110304

出版商:Society of Plastics Engineers, Inc.    

年代:1971

数据来源: WILEY

摘要:

AbstractThe effects of temperature, strain rate and filler content on tensile properties of SAN/glass bead composites are studied. A point of discontinuity on the stress‐strain curves for unannealed composites is investigated, annealing results in smooth curves with no discontinuities. A simple model for the filler effect on yield stress is suggested and shown to be in a good agreement with experimental data. A double shifting procedure to account for the temperature and filler effects on yield stress as a function of strain rate is proposed. A single master curve that can be represented by the equation:\documentclass{article}\pagestyle{empty}\begin{document}$$ \frac{{\sigma yc}}{{{\rm 1 - 1}{\rm .21}\phi ^{{\rm 2/3}} }} = A + B\,{\rm ln (}\dot \epsilon a_T) $$\end{document}relates composite yield stress to strain rate, temperature and filler volume fractio

ISSN:0032-3888    

DOI:10.1002/pen.760110305

出版商:Society of Plastics Engineers, Inc.    

年代:1971

数据来源: WILEY

摘要:

AbstractThis article uses Graessley's theory of viscosity to predict the flow curve for several high‐density and low‐density polyethylene melts using the molecular weight distribution data obtained from the gel permeation chromatograph. The agreement with the experimental flow curve obtained from the Weissenberg rheogoniometer and the Instron rheometer was not quantitative for many high‐density polyethylenes studied here. For the low‐density polyethylenes, it was shown that the agreement between the theory and the experiment was good even though the molecular weight distribution data were not corrected for long‐chain branching. For these samples, the experimental relaxation time τ0obtained by superposition of the data with the theoretical master curve was of the order of the Rouse relaxation time τR. The systematic increase in the ratio τR/τ0was ascribed to the increase in the molecular weight or to the increased number of long

ISSN:0032-3888    

DOI:10.1002/pen.760110306

出版商:Society of Plastics Engineers, Inc.    

年代:1971

数据来源: WILEY

摘要:

AbstractA correlation is developed between the melt elasticity and temperature, the melt elasticity being defined by the normal stress difference. The correlation follows the form of the Arrhenius equation, for the temperature range tested, for high density polyethylene and polypropylene melts. Measurements were taken using the capillary rheometer which is described in detail in the author's earlier publications. The author further presents a correlation between the pressure drop at the entrance of a capillary and the residual pressure at the exit of the capillary (exit pressure). The correlations presented in the paper support the author's earlier contention that the exit pressure is indeed a manifestation of elastic behavior.

ISSN:0032-3888    

DOI:10.1002/pen.760110307

出版商:Society of Plastics Engineers, Inc.    

年代:1971

数据来源: WILEY

摘要:

AbstractGlass‐reinforced thermoplastics are being considered in many structural applications and fabricators require design information on these materials. Basic creep data are, in many cases, the most useful for design purposes. The work reported here concerns the development of methods of increasing our efficiency in generating creep data. The methods developed are applicable to polypropylene and coupled, glass‐reinforced polypropylene. A stress‐time superposition procedure has been found valid for extending creep data generated on coupled glass‐reinforced polypropylene at several glass levels and at temperatures of 23 a

ISSN:0032-3888    

DOI:10.1002/pen.760110308

出版商:Society of Plastics Engineers, Inc.    

年代:1971

数据来源: WILEY

摘要:

AbstractA large number of composite materials are polyphase systems in which one phase exhibits time‐dependent properties. This paper presents an analysis of the stress redistribution in such a viscoelastic material system under the influence of applied external loads. In order to perform this study an appropriate idealized model, a series of which would tend to approximate the composition of a polyphase material, is formulated. The solution of the time‐dependent stress field is obtained by applying the “correspondence principle” to the elastic stress field solution which, for the selected model, has previously been obtained in numerical form.Application of the solution to a model of an actual polyphase composite material system yields results which clearly indicate that, under certain normally encountered conditions of external loading, the principal stresses in certain areas of such a system will increase significantly wi

ISSN:0032-3888    

DOI:10.1002/pen.760110309

出版商:Society of Plastics Engineers, Inc.    

年代:1971

数据来源: WILEY

摘要:

AbstractThe mechanical performance of fiber glass epoxy, cross‐plied laminates having either ductile or brittle matrices, was evaluated in tension. The laminates with ductile matrices have higher initial strength, slower crack propagation in the transverse layers and higher ultimate stress and strain. In both the ductile and brittle systems, the laminae have higher strength, stiffness and toughness than equivalent unidirectional composites. This improved performance results from the interaction between the perpendicular layers which gives them additional stiffness due to shear and transverse coupling effects and also increases the resistance of each individual layer to crack propagation and plastic flo

ISSN:0032-3888    

DOI:10.1002/pen.760110310

出版商:Society of Plastics Engineers, Inc.    

年代:1971

数据来源: WILEY

摘要:

AbstractCobalt promoters presently used in the polyester processing industry suffer from many shortcomings ranging from shelf instability to strong discoloration of the resins and relatively poor activity. This paper describes the various performance improvements obtainable with coordination complexes of cobalt which can be used as polymerization accelerators in presence of organic peroxide initiators. These complexes appear to present significant advantages over the conventional cobalt carboxylates. Catalytic activity up to ten times that of cobalt soap was recorded with some complexes in various resin systems, without deleterious effects on physical properties. As gel‐cure modifiers, the compounds evaluated seem to increase the long term shelf stability of pre‐promoted resins while reducing the discoloration and air inhibition during the curing process of polyester thin fi

ISSN:0032-3888    

DOI:10.1002/pen.760110311

出版商:Society of Plastics Engineers, Inc.    

年代:1971

数据来源: WILEY