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Birefringence and residual stresses ...

Shyu, Goang-Ding.

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Birefringence and residual stresses in molded articles of amorphous polymers.

Record Type:	Language materials, printed : Monograph/item
Title/Author:	Birefringence and residual stresses in molded articles of amorphous polymers./
Author:	Shyu, Goang-Ding.
Description:	265 p.
Notes:	Adviser: A. I. Isayev.
Contained By:	Dissertation Abstracts International54-10B.
Subject:	Chemistry, Polymer. -
Online resource:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=9409223

Birefringence and residual stresses in molded articles of amorphous polymers.
Shyu, Goang-Ding.

Birefringence and residual stresses in molded articles of amorphous polymers. - 265 p.

Adviser: A. I. Isayev.

Thesis (Ph.D.)--The University of Akron, 1993.

This research is an attempt to understand the birefringence and stress development in injection molded products from basic studies. Stress relaxation experiments with simultaneous measurements of the relaxation modulus and the strain-optical coefficient were conducted on polystyrene (PS) and polycarbonate (PC) over a wide range of temperatures from above to below the glass transition temperature. Master curves of the modulus and the strain-optical coefficient of PC and PS were obtained by using the time-temperature superposition principle. The master curve of the strain-optical coefficient C$\sb\epsilon$ of PS shows that C$\sb\epsilon$ is initially positive, relaxes to zero and afterwards becomes negative. At a certain point C$\sb\epsilon$ attains its minimum value and then becomes a monotonic increasing function of time, approaching zero at large time. C$\sb\epsilon$ of PC is always positive and relaxes toward zero.Subjects--Topical Terms:

1018428
Chemistry, Polymer.

Birefringence and residual stresses in molded articles of amorphous polymers.
LDR:03404nam 2200301 a 45 001 951184
005 20110609
008 110609s1993 eng d
035 $a (UMI)AAI9409223
035 $a AAI9409223
040 $a UMI $c UMI
100 1 $a Shyu, Goang-Ding. $3 1275166
245 1 0 $a Birefringence and residual stresses in molded articles of amorphous polymers.
300 $a 265 p.
500 $a Adviser: A. I. Isayev.
500 $a Source: Dissertation Abstracts International, Volume: 54-10, Section: B, page: 5175.
502 $a Thesis (Ph.D.)--The University of Akron, 1993.
520 $a This research is an attempt to understand the birefringence and stress development in injection molded products from basic studies. Stress relaxation experiments with simultaneous measurements of the relaxation modulus and the strain-optical coefficient were conducted on polystyrene (PS) and polycarbonate (PC) over a wide range of temperatures from above to below the glass transition temperature. Master curves of the modulus and the strain-optical coefficient of PC and PS were obtained by using the time-temperature superposition principle. The master curve of the strain-optical coefficient C$\sb\epsilon$ of PS shows that C$\sb\epsilon$ is initially positive, relaxes to zero and afterwards becomes negative. At a certain point C$\sb\epsilon$ attains its minimum value and then becomes a monotonic increasing function of time, approaching zero at large time. C$\sb\epsilon$ of PC is always positive and relaxes toward zero.
520 $a Simulations of the residual birefringence in freely quenched plates of PS and PC were performed by using the linear viscoelastic and photoviscoelastic constitutive equations for the mechanical and optical properties, respectively, and the first order rate equation for volume relaxation. The predictions are in fair agreement with experimental measurements. At temperatures higher than 105$\sp\circ $c , the residual birefringence in freely quenched PS plates is negative at the center and positive at the surface, while at temperatures close to the glass transition temperature, the birefringence becomes positive at the center and negative at the surface. The birefringence in freely quenched PC plates is positive at the center and negative at the surface.
520 $a The injection molding process was simulated by using a compressible nonlinear viscoelastic constitutive equation. Three stages of the injection molding cycle-filling, packing and cooling, were included in the simulation. The residual thermal birefringence is treated as that in a freely quenched plate. The simulation shows that without packing, the birefringence peak near the surface results from the frozen flow birefringence while the birefringence at the core is due to the residual thermal birefringence. With packing, a second birefringence peak appears between the first peak and the center. Simulation shows that this second peak is a result of the compressible flow in the packing stage. The predicted birefringence profiles and extinction angle profiles agree with corresponding experimental measurements.
590 $a School code: 0003.
650 4 $a Chemistry, Polymer. $3 1018428
650 4 $a Engineering, Mechanical. $3 783786
650 4 $a Plastics Technology. $3 1023683
690 $a 0495
690 $a 0548
690 $a 0795
710 2 0 $a The University of Akron. $3 1018399
773 0 $t Dissertation Abstracts International $g 54-10B.
790 $a 0003
790 1 0 $a Isayev, A. I., $e advisor
791 $a Ph.D.
792 $a 1993
856 4 0 $u http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=9409223