The extensional flow of poly(methyl methacrylate) and high-impact polystyrene at thermoforming temperatures
Article first published online: 9 MAR 2003
Copyright © 1975 John Wiley & Sons, Inc.
Journal of Applied Polymer Science
Volume 19, Issue 5, pages 1209–1220, May 1975
How to Cite
Lai, M. O. and Holt, D. L. (1975), The extensional flow of poly(methyl methacrylate) and high-impact polystyrene at thermoforming temperatures. J. Appl. Polym. Sci., 19: 1209–1220. doi: 10.1002/app.1975.070190501
- Issue published online: 9 MAR 2003
- Article first published online: 9 MAR 2003
- Manuscript Revised: 9 OCT 1974
- Manuscript Received: 12 AUG 1974
The work described in the present paper was performed to establish stress–strain–time relationships at plastic sheet thermoforming temperatures. The relationships are correlated with sheet-forming “formability”. Specimens of poly(methyl methacrylate) at 165°C and high-impact polystyrene at 122°C were extended to large strains at constant cross-head velocities. Initial strain rates were between 4.2 × 10−3/sec and 1.6 × 10−1/sec. It was found that the flow stress σ was related to the true strain ε and the elapsed time t by a relation σ = Ktm′εn, where K is a constant and n and m′ are indices. The value of n for both materials was approximately one. The value of m′ was −0.052 and −0.33 for poly(methyl methacrylate) and high-impact polystyrene, respectively. Tests were also performed in which the cross-head velocity was increased in steps. It was found that the flow stress in these tests followed the same relationship as in the constant cross-head velocity tests.