THIN-FILM AND BULK DEFORMATION-BEHAVIOR OF POLY(ETHER ETHER KETONE) POLY(ETHER IMIDE) BLENDS

The deformation behaviour of amorphous thin films of poly(ether ether ketone) (PEEK)/poly(ether imide) (PEI) blends was investigated over a wide temperature range by optical and transmission electron microscopy . All the materials showed localized shear deformation at temperatures well below T-g. In pure PEI and in blends with up to 60 wt% PEEK cont ent, a transition from shear deformation to disentanglement crazing oc curred as the temperature was raised. However, this transition was abs ent in PEEK, which deformed by shear over the whole temperature range, and similar behaviour was found for PEI/80 wt% PEEK. It is argued tha t at high PEEK content disentanglement crazing is suppressed by strain -induced crystallization and some evidence for crystalline order in de formed regions of initially amorphous PEEK thin films was obtained by electron diffraction. The thin film deformation behaviour of the blend s was also shown to be consistent with their bulk deformation behaviou r, a high temperature ductile-brittle transition being observed at low PEEK content in tensile tests.