Copolycarbonate Derived from Carbon Dioxide as Toughness Improvement for Poly (lactic acid)

Abstract

Abstract This work aimed to study the preparation of copolycarbonate based on carbon dioxide (CO2) and 1, 2-butylene oxide using a self-prepared zinc glutarate (ZnGA) as a catalyst. The effect of reaction time, temperature and pressure on yield of copolycarbonate products was investigated. The chemical structure was confirmed by NMR and FTIR spectra. The molecular weight and its distribution were determined by GPC. The thermal stability of copolycarbonate was measured by TGA. The synthesized copolycarbonate was melt-blended with Poly (lactic acid) or PLA to investigate the effect of copolycarbonate contents on mechanical properties of PLA. The results showed that the synthesized copolycarbonate was poly (butylene carbonate) (PBC) as indicated by NMR and FTIR results. The optimum yield of PBC was 52.21% synthesized at 95 °C, 70 bar, and 52 h of a reaction time. Based on GPC results, the molecular weight distribution of PBC was broad and no by-product such as cyclic carbonate could be detected. The TGA thermogram of PBC showed the onset temperature of 200 °C, implying the decomposition of small residual molecules. The average molecular weight was found to be 25,270 Da. The melt-blending of PLA/PBC (90/10 and 80/20 w/w) was performed with and without a reactive agent (peroxide) in an internal mixer at 190 °C and the rotor speed of 60 rpm. The torque value of reactive PLA/PBC (PLA/PBC/Per) decreased when compared to non-reactive PLA/PBC at the same blend ratio. The morphology of PLA/PBC and PLA/PBC/Per as illustrated by SEM showed that PLA/PBC was immiscible but after adding peroxide, the compatibility between PLA and PBC was improved. The elongation at break of PLA/PBC/Per (80/20/0.001phr) increased from 7.74 % to 161.38 % as well as the impact strength of PLA/PBC (80/20) increased 3 times when compared with that of neat PLA.