MICRODEFORMATION MECHANISMS IN METHYL METHACRYLATE-GLUTARIMIDE RANDOMCOPOLYMERS

Transmission electron microscopy (TEM) has been used to investigate th e microdeformation mechanisms in thin films (< 1 mu m) of MMA-glutarim ide copolymers of various compositions ranging from 36 to 76 mol% glut arimide. These polymers all have an entanglement density of similar to 5 x 10(25) m(-3), which is of the same order as that in poly(methyl m ethacrylate) (PMMA). Crazing is known to be the dominant deformation m echanism in thin films of PMMA tested at room temperature. As the glut arimide content is increased in the copolymers, however, motions assoc iated with formation of shear deformation zones (DZs) are facilitated, and these become increasingly competitive with scission crazing in th in films. The presence of the MMA groups may nevertheless continue to hinder large-scale chain motions associated with high-temperature dise ntanglement crazing, since it was found that the absolute temperature for the onset of disentanglement in the copolymers remained similar to that in PMMA (ca. 80 degrees C for the strain rates used here), and w as essentially independent of the composition and the glass transition temperature (T-g). Copyright (C) 1996 Elsevier Science Ltd.