Characterisation of PC/ABS blend during 20 reprocessing cycles and subsequent functionality recovery by virgin additives

Abstract

PC/ABS blend (a.k.a CS) is one of the most popular engineering plastics to date, frequently considered as a good alternative to PC or ABS. To estimate the potential to recycle and reprocess CS, we characterised the thermal, rheological and mechanical behaviour of CS reprocessed 0 to 20 times in real industrial facilities and, furthermore, unprecedentedly attempted to modify the 20-time reprocessed CS until its functionality within 15% deviation from the virgin CS. Consistent thermal weight loss (30% at 300-450 °C and 40% at ~470 °C) and Tg points (at ~100 °C) of CS from various cycles of reprocessing reflected the associated high thermal stability. However, increased stress values (from 4.71 to 5.23 kgf mm−2) and melting index (from 40 to 66 g (10 min)−1) but decreased stain (from 27.2 to 11.7%), impact strength (from 87.7 to 14.2 J m−1) and torque values (from 71 to 49 N m−1) suggested that CS underwent polymer chain breaks during reprocessing and became stiffer. Recovery of the 20-time reprocessed CS was achieved by adding ~30% (w/w) virgin PC and ABS together with 1.5% (w/w) of chain extender and 2% (w/w) of styrene maleic anhydride (SMA) simultaneously. The study demonstrated the potential for recovering repeatedly reprocessed PC-based polymer blends and a new way of recycling polymer resource for environmental protection.