Casein was grafted with acrylonitrile and with a binary mixture of acr
ylonitrile and n-butyl methacrylate. Mechanical properties and the fra
cture of these films were studied at different temperatures. Due to po
ssible transition, fracture behaviour changed ca. 60-degrees-C in both
systems. The effect of the polymer (grafted chains and homopolymer) p
resent in the system affected the morphology and the fracture behaviou
r of casein films grafted with binary mixtures of the monomer.