THE ROLE OF FLAME RETARDANT ADDITIVES IN THE FRACTURE TOUGHNESS OF HIGH IMPACT POLYSTYRENE

摘要

The most common flame retardant systems used in High Impact Polystyrenes (HIPS) are based on a synergistic mixture of antimony trioxide and a bromine compound. Flame retarded grades of HIPS are used in a range of applications including television, computers and other electronic component housings, due to their combination of good physical and electrical properties. However, because of the trend to move towards lighter, thinner-walled, mouldings, these properties are coming under even greater scrutiny. Unfortunately, the presence of both antimony and the bromine compounds can cause large reductions in mechanical properties, particularly impact values. The mechanical properties of halogen based flame retardant HIPS has been investigated with particular emphasis on the impact properties. The influence of the particle size of antimony trioxide and decabromodiphenyl oxide (DBDPO), together with the loading level of the antimony trioxide, DBDPO, and an impact modifier were investigated, and compared against a control of unfilled HIPS. Flexural properties were found to be insensitive to these variables underlining a shortfall of this test method. However, impact and fracture toughness tests showed that the particle size of the antimony trioxide, and loading levels of DBDPO and impact modifier, can have a significant affect on these properties. Staining the HIPS with osmium tetroxide (OsO_4) allowed the rubber phases to be identified and the additives location to be determined within the polymer system. It was found that the additives were always located in the polystyrene matrix and that a relationship existed between the additives particle size and the rubber phase size.