This is a review on polymer toughening by non-elastomer. The toughening mechanisms of rubber-modified plastics are reviewed first. Then the concept of Rigid Organic Filler (ROF) and Cold-drawing

and methods of analysing the toughened system are introduced

and experiments in polymer blends consisting of brittle polymer particles dispersed in ductile polymers are cited to explain them. By comparision with the toughening mechanisms of rubber-modified plastics

it is concluded that toughening by such non-elastomer is a new mechanism and is a potential new route to toughened plastics.