Assessment of compliance and stress-relaxation data for polystyrene

Consideration is given to available experimental results in the literature for the compliance and stress relaxation of polystyrene. It is shown that s hear-compliance data from three independent sources correlate very well ove r the entire glass-rubber transition. On the other hand, available elongati onal stress-relaxation data from four independent sources indicate a lack o f agreement, with overall discrepancy on the order of four decades in time for E(t) over the entire transition region. By making use of the Knoff-Hopk ins algorithm, the Leaderman approximation and a new procedure based on a l east-squares collocation method, the above correlation for J(t) is used to generate G(t) which, in turn, is used to obtain E(t), assuming a constant c ompressibility. The resulting correlation indicates the need for further ex perimental work in this area. (C) 1999 The Society of Rheology. [S0148-6055 (99)00604-5].