Three dimensional chaotic mixing of polystyrene with polyethylene

Polystyrene (PS) was blended with low-density-polyethylene (LDPE) in a self-made three dimensional chaotic mixer. Evolvement of the minor phase and its effect on toughness of the blend were investigated. Examination by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) show that minor phase changed from macroscopical droplets to sheets of varied thickness, then to fibrils and to microcosmic droplets as the period numbers increases. Ultimately, there are fibrils of high aspect ratio and many uniform sized droplets in the blend. Compatibilizer polystyrene/polyethylene-propylene (SEP) tend to enhance the formation of this structure. Impact strength tests showed that no improvement occurred without compatibilizer due to badly interface adhesion. However significant improvement of toughness can be achieved with a little compatibilizer (0.45% by weight). The maximum impact strength was 90.9% higher than that of pure PS.