Quasi-static and dynamic compressive behaviour of poly(methyl methacrylate) and polystyrene at temperatures from 293 K to 363 K.

Flow stress, Young’s Modulus, energy and strain of fracture of poly(methyl methacrylate) (PMMA) and polystyrene (PS) were studied under compressive loading at strain rates of 10⁻⁴–10 s⁻¹ and temperatures from 293 K to temperatures ∼20 K below T _g. It was found that the energy of fracture shows an increase in the quasi-static strain rate (10⁻⁴–10⁻³ s⁻¹) region and becomes constant in the low strain rate (10⁻²–10 s⁻¹) region, while the strain of fracture shows a slow decrease with rate over the strain rate range tested. The activation energies and volumes of PMMA and PS at yield stress, 20% and 30% strain were evaluated using Eyring’s theory of viscous flow. Δ G was found to be constant for all strain rates and strains for both PMMA and PS. The activation volume for both materials increased as a function of strain. [ABSTRACT FROM AUTHOR]