Characterization of recycled polycarbonate/polybutylene terephthalate blends

Polycarbonate (PC)/polybutylene terephthalate (PBT) blends (CBs) represent a good compromise between the properties of PC and PBT and are among the most popular engineering plastics today. To evaluate the capability of recycled and reprocessed CBs, the physical and mechanical properties of 0 to 20 times reprocessed CBs were characterized, and an attempt was made to modify a 20-time reprocessed CB to reach ≥85% of the functionality of a virgin CB. Generally, the thermal weight loss (30% at 300–450°C and 40% at ~470°C) of the CBs varied little with the reprocessing cycles, reflecting their high thermal stability. The increased melting index (from 18.7 to 92.0 g (10 min)–1) but decreased stress values (from 6.08 to 4.99 kgf mm–2), strains (from 79.0 to 29.1%), impact strength (from 144 to 14.7 J m–1) and torque values (from 82 to 60 N m–1) with reprocessing cycles suggest that the CBs undergo thermal/mechanical decomposition when reprocessing and become thereafter stiffer. Satisfactory modification of the 20 times reprocessed CB succeeded simply via adding ~30% (w/w) virgin PC and PBT. Adding styrene maleic anhydride and a chain extender failed to improve the stress values of reprocessed CBs, probably due to their weak interaction with the PC and PBT molecules.