Time Temperature Superposition in Heterophase Block Copolymers.
CALIFORNIA UNIV BERKELEY DEPT OF CHEMICAL ENGINEERING
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The viscoelastic behavior of a styrene-butadiene-styrene block copolymer was studied in order to examine the validity of the Time Temperature Superposition Principle in heterophase polymers. It is found that by using an additive model, the shift factor curve can be computed. Stress relaxation isotherms over a wide temperature range can be easily superposed into a smooth master curve with these computed shift factors. The master curve compares favorably with other mechanical data determined at long times and at a high frequency. However, it is pointed out that this apparent thermorheological simplicity is strictly valid only in the region where one of the relaxation mechanisms dominates. Dynamic mechanical data illustrating the effect of multiple relaxations are presented. Author
- Elastomers and Rubber