Fracture initiation and crack propagation of acrylonitrile-butadiene-styrene (ABS) in organic solvents

Abstract

The effects of organic liquid environments on the fracture behaviour of acrylonitrilebutadiene-styrene (ABS) have been investigated. Fracture initiation experiments showed that K~, (K~ being the stress intensity factor at crack/craze initiation), could be meaningfully correlated with the solvent solubility parameter (Ss) of the different liquid environments and had a minimum value at 8s = 6p, where 6p was the solubility parameter of ABS. For the rangeof organic liquids used, hydrogen bonding did not have any significant effects on the correlations. It was demonstrated that the K~-8, correlations could also be usefully extended to other materials such as plain and glass-filled polystyrenes. At a common crack speed (&), the fracture toughness (R) values in crazing liquids (i.e. alcohols) were greater than those in cracking solvents (i.e. acetone, benzene, toluene, etc.) which usually caused a dissolution effect on the plastic. From crack propagation experiments, and using fracture mechanics analyses, definite R(&) and Kc (~) relationships for ABS immersed in toluene, carbon tetrachloride and methanol were determined. These experimental results showed that crack propagation was relaxation controlled and agreed well with a recent theoretical analysis due to Williams and Marshall for environmental crack and craze growth in polymers. Finally, SEM pictures were presented to show the remarkable differences in the fracture morphologies of ABS in both crazing and cracking liquid environments.