NYLON-6 RUBBER BLENDS .2. TEMPERATURE EFFECTS DURING HIGH-SPEED DEFORMATION

The deformation zone of fractured nylon-6/ethylene-propylene rubber specimens was studied using scanning electron microscopy (SEM). In this deformation zone three distinct layers were observed. In the main part of the stress-whitened zone only cavitation was visible. From 150-5 mum below the fracture surface, massive plastic deformation was observed. Directly under the fracture surface there was a layer about 3-5 mum thick where no cavitation or deformation was visible. This zone without cavitation was only visible when the specimen was fractured at high deformation rates. It is proposed that this top layer consists of material which was molten during fast crack propagation under adiabatic conditions. This hypothesis has been confirmed by model calculations and experiments. When the deformation rate is very high (greater than the impact velocities) plastic deformation is not homogeneous throughout the deformation zone, but confined to layers.