YIELDING AND PLASTIC BEHAVIOR OF AMORPHOUS ATACTIC POLY(OXYPROPYLENE)UNDER UNIAXIAL COMPRESSION - AN ATOMISTIC MODELING APPROACH

The yielding and plastic behaviour of atactic poly(oxypropylene) (a-PO P) was simulated under the uniaxial compression condition using atomis tic modelling, and compared with the result under the uniaxial extensi on condition. Typical stress-strain curves showing yielding and plasti c behaviour were obtained under the uniaxial compression condition. It was observed that the stress under uniaxial compression is greater th an that under uniaxial extension. This observation suggests that the d ifference of stress level between the two conditions is not related in trinsically to the structural defects in the sample. When the energeti c state of a-POP was analysed by monitoring the change of energy compo nent with strain, it revealed that the change of total energy with str ain was governed dominantly by non-bonded interaction, such as van der Waals and Coulombic interaction. The role of Coulombic interaction is more important under compression than under extension. (C) 1998 Elsev ier Science Ltd. All rights reserved.