Synthesis strategies in the preparation of high impact polystyrene with different type of particles as the dispersed phase, towards a balance between impact strength and gloss

Three different synthesis strategies based on the in situ pre-polymerization process were employed in order to obtain High Impact Polystyrene (HIPS) with different type (morphology and size) of particles as the dispersed phase, achieved by the use of two styrene-butadiene rubbers (SBR) in the initial recipes. The rubbers used were tapered polystyrene/polybutadiene copolymers with a polystyrene/polybutadiene composition of 10/90 and 40/60 wt%. Results were discussed in terms of physical–chemical, morphological, mechanical and optical parameters. A combination of two or three types of particle morphologies, i.e. salami, core–shell and droplets in the same sample were evidenced by Transmission Electron Microscopy analysis, independently of the strategy employed. The grafting degree, volume fraction of the dispersed phase and impact strength were positively affected by the increase of the amount of 10/90 SBR in the recipe. Several HIPS samples showed a good balance between impact strength and gloss, particularly those obtained from the strategy herein named as melt blending.