The effect of different peroxides on physical and chemical properties of poly (lactic acid) modified with maleic anhydride

Maleic anhydride grafting onto poly(lactic acid) (PLA) was conducted by reactive processing in a torque rheometer according to a 2(4) factorial design, in which the maleic anhydride and peroxide concentrations, peroxide type and dispersion medium were varied. Physical and chemical properties of modified PLA were investigated by assessing the effects of using two types of organic peroxides, dicumyl peroxide (DCP) and 2,5-dimethyl-2,5-di(t-butylperoxy) hexane (DHBP) in different suspensions (neat and calcium carbonate). The modified poly(lactic acid) was characterized by size-exclusion chromatography, titration of acid groups and nuclear magnetic resonance (NMR) spectroscopy. Results showed that the chemical modification was effective in increasing the acidity content of PLA, despite the polymer molar mass reduction. The independent variable peroxide concentration was one that most affected the acidity percentage and polymer molar mass. Although DHBP dispersed in calcium carbonate demonstrated to be the most effective in increasing the acidity of PLA, both peroxides are suitable and have similar effects on chemical modification of PLA with MA.