Processing history induced birefringence and the mechanical behavior of anisotropic filaments of virified polymethylmethacrylate and polystyrene
Date Issued
June 1, 1980
Author(s)
Boateng, Fredson
Advisor(s)
James L. White
Additional Advisor(s)
D C Bogue
J F Fellers
J. E. Spruiell
Abstract
The purpose of this experimental study was to investigate the processing history induced birefringence and the mechanical behavior of anisotropic filaments of vitrified polymethylmethacrylate and polystyrene. Oriented filaments have been prepared by melt spinning and by oven drawing. Analysis of the internal stresses in the filaments indicates that even though the overall birefringence is made up of contributions from molecular orientation and thermal stresses, the thermal stress contribution is relatively much greater in polymethylmethacrylate than in polystyrene. The non-linear birefringence-stress behavior obtained for polymethylmethacrylate is interpreted in terms of this significant effect of thermal stresses. This effect is greater in melt spinning than in oven drawing.
The mechanical properties of polymethylmethacrylate filaments at room temperature are obtained with 100% per minute strain rate. The modulus, yield stress and tensile strength all generally increase with birefringence, while the percent elongation-to-break initially increases to a point and then decreases showing a discontinuity at a birefringence of about -0.35 x 10-3. The torsional modulus is little affected by birefringence, and no correlation is found between Poisson's ratio and birefringence. In general the mechanical properties are little or not affected by thermal stress.
Degree
Master of Science
Major
Polymer Engineering
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Thesis80B638.pdf
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