Reactive functionalization of poly(lactic acid), PLA: Effects of the reactive modifier, initiator and processing conditions on the final grafted maleic anhydride content and molecular weight of PLA

Abstract

Abstract A response surface methodology (RSM) design was used to analyze the effects of maleic anhydride (MA) and 2,5-bis( tert -butylperoxy)-2,5-dimethyl hexane (Luperox or L101) content, and TSE screw speed on the degree of grafted MA (MA g ) and number average molecular weight ( M n ) of maleated PLA (PLA- g -MA), which can be used as a reactive compatibilizer in production of PLA blends with various components. PLA- g -MA's FTIR peaks indicated that MA was grafted onto the PLA backbone and oligomeric MA was also present. A maximum of 0.52 wt% MA g determined by titration was achieved at the expense of a 50% reduction of M n and an increase in the polydispersity index to around 2.0. Generally, increasing L101 increased the degree of grafting and decreased M n . L101 and MA g had a large effect on the stability of PLA- g -MA's M n during storage. Nominally, amounts of MA equal to 4.5 wt%, L101 between 0.45 and 0.65 wt%, and screw speed of 20 rpm provided the optimal conditions for grafting MA onto PLA.