Doctoral Dissertations
Orientation development and mechanical properties of multiaxially oriented fabricated thermoplastics
Date of Award
12-1983
Degree Type
Dissertation
Degree Name
Doctor of Philosophy
Major
Polymer Engineering
Major Professor
Joseph E. Spruiell
Committee Members
Edward S. Clark, Larry C. W.
Abstract
The development of orientation by various processes producing multiaxial orientation was studied. The processes studied included the blow molding process without and with a rotating outer and a counter rotating inner core mandrel, tubular film blowing over a mandrel and biaxial stretching using a T. M. Long stretching machine. The studies were carried out on polystyrene and polyethylene using measurements of birefringences, wide angle x-ray diffraction (V/AXD) pole figures, and small angle x-ray scattering (SAXS) patterns.
Both polystyrene and polyethylene experimental results are interpreted in terms of White and Spruiell's biaxial orientation factors.
Uniaxial, biaxial and various intermediate states of oriented polystyrene films were prepared in a biaxial stretching machine. A wide range of stretch ratios up to 7.2 was used.
The prediction of birefringences of the stretched PS films are generally in good agreement based on a convected Maxwell model and Rheo-Optical Law with the experimental results.
Generally, the mandrel-films develop lower orientation than the conventional blown films. The level of orientation is interpreted by means of the applied stress field.
Coventional blow molded bottles were made from HOPE, LDPE and LLDPE resins. The pole figure of HDPE bottles indicates slight a-axis orientation toward the circumferential direction. The b-axes which are the lamellar crystal grow directions tend to be parallel to the thickness direction. The morphological model of HDPE blow molded bottle is described in terms of elongated spherulites.
The level of orientation and the tendency toward biaxiality of both polystyrene and HDPE bottles from the rotating die is slightly greater than for bottles produced using the conventional die.
It is found that crystallization of polyethylene bottles and films involves both an increase in level of polymer chain orientation, and an increased tendency towards biaxiality.
Mechanical properties of the stretched PS films were correlated with the level of orientation. Brittle to ductile transition phenomena were observed and discussed
Mechanical properties measured at various directions in the plane of HDPE blown films are also described.
Recommended Citation
Choi, Kyung Ju, "Orientation development and mechanical properties of multiaxially oriented fabricated thermoplastics. " PhD diss., University of Tennessee, 1983.
https://trace.tennessee.edu/utk_graddiss/13016