Studies conducted by many workers in recent years have indicated substantial anisotropies in injection molded thermoplastics. These anisotropies have been associated with differences in morphology (crystallinity) and orientation (shrinkage and birefringences) at various positions in the molding. They are reflected by anisotropies in tensile properties measured at different points or in different directions. However, no work has been reported to quantitatively relate the distributions in tensile properties. The present work represents an attempt to meet this challenge. / Microstructure determination is achieved by making the following measurements on microtomed specimens at different positions in the polyethylene moldings: density, sonic speed, birefringence, wide-angle X-ray diffraction, dichroic ratio, and polarized light photomicrography. The above tests yield data relating to crystallinity and orientation functions for both the crystalline and amorphous phases. They also yield sufficient data to check the consistency of results obtained by the different techniques. Tensile properties are measured on microtomed samples obtained from the same regions tested for microstructure. Finally, the distributions of tensile and sonic moduli in the molding are estimated by employing some of the theoretical techniques proposed in the literature. The results show very good agreement between theoretical predictions and experimental data relating to the distributions of both sonic moduli and tensile moduli.

In the extrusion blow molding process the shape and thickness distribution of the finished container depend on the dimensions of the parison at the time of inflation. In particular, the processes of swell and sag act to cause a variation of parison dimensions between the time the melt emerges from the die and the moment of inflation. / In the present study the effects of die geometry, extrusion velocity and the rheological properties of the resin on parison behavior were studied. Four annular dies (a straight, a diverging and two converging dies) and three high density polyethylene resins were used. To study the individual contributions of swell and sag to the overall parison behavior, two types of experiments were carried out. First, swell was studied in the absence of sag by extruding the parison into an isothermal oil bath. Both diameter and thickness swells were measured as functions of time. Then combined effect of swell and sag was studied by extruding the parison into an isothermal air oven. / A simple lumped parameter model was developed to predict the length of the parison using the swell data, storage modulus and process variables.

Thesis (Ph.D.)--Hong Kong University of Science and Technology, 2008. / Includes bibliographical references (leaves 194-209). Also available in electronic version.

Thesis--Auburn University, 2005. / Abstract. Vita. Includes bibliographic references (p.59-62).

Dissertation (PhD)--University of Stellenbosch, 2007. / Bibliography. Also available via the Internet.

Thesis (M.S.)--Oregon State University, 2009. / Printout. Includes bibliographical references (leaves 104-110). Also available on the World Wide Web.

Thesis (M.S.)--Ohio State University, 2008. / Title from first page of PDF file. Includes bibliographical references (p. 106-107).

Thesis (Ph. D.)--Ohio State University, 2004. / Title from first page of PDF file. Document formatted into pages; contains xxi, 238 p.; also includes graphics Includes bibliographical references (p. 231-238). Available online via OhioLINK's ETD Center

Thesis (Ph. D.)--Ohio State University, 2004. / Title from first page of PDF file. Document formatted into pages; contains xvi, 206 p.; also includes graphics (some col.). Includes bibliographical references (p. 167-173). Available online via OhioLINK's ETD Center

Thesis (M. Phil.)--University of Hong Kong, 1998. / Includes bibliographical references (leaves 174-176).