No description available.

No description available.

No description available.

In the extrusion blow molding process, the behaviour of the parison prior to inflation is of central importance. Properties of the finished article, such as wall thickness and thickness uniformity, are determined by the simultaneous phenomena of swell and sag. / In the present study, an apparatus was built to study the behaviour of the extrudate from an annular die under isothermal conditions. First, sag was eliminated by extruding into an oil bath, and both thickness and diameter swell were determined as functions of time. Then, extruding into heated air, sag behaviour was observed. / These procedures allowed the study of the individual contributions of swell and sag to the overall parison behaviour. / Three high density polyethylene resins and a polypropylene resin were studied. The materials were thoroughly characterized to obtain the traditional rheological properties. In addition, an extensional rheometer was modified to measure the viscosity under uniaxial extension. / A model to predict the total length of the parison at any given time is proposed. This model is expressed in terms of rheological properties of the materials and process variables only.

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That some kind of network plays a central role in the rheology of high molecular weight, amorphous polymers is inferred from such phenomena as a change in the slope of the curve of viscosity versus molecular weight and the plateau in the stress relaxation curve. However, these data give no explicit information about the rates of network destruction and reformation. A new method which involves the reduction in shear rate in transient shearing flow was used to obtain such network kinetics information for three polyethylene melts at 170(DEGREES)C. / Other methods of characterization have also been used. These include steady simple shear, small amplitude oscillatory shear, large amplitude oscillatory shear and transient uniaxial extensional flow. All of the above methods involve different types of deformation in both linear and nonlinear viscoelastic regions. These data were used to test the predictive abilities of two constitutive equations inspired by network theory.

No description available.

Thesis (Ph. D.)--University of Washington, 2008. / Vita. Includes bibliographical references (p. 85-100).

Proefschrift--Utrecht. / Text in English. Includes index. "Stellingen" (2 leaves inserted). Bibliography: p. [85].

Thesis (Ph. D.)--West Virginia University, 2005. / Title from document title page. Document formatted into pages; contains x, 160 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 149-156).