An investigation of poly(lactic acid) (PLA) and maleic (MAH) anhydride graft copolymer (PLA-g-MAH) and its blends with polyethylene glycol (PEG)

Poly(lactic acid) (PLA) was reacted in the melt state with maleic anhydride (MAH) using a Haake torque rheometer chamber to produce graft copolymers. 5-20 wt% of maleic anhydride was used at a temperature of 160{dollar}spcirc{dollar}C with t-butyl peroxide as an initiator. These products were purified through precipitation by using acetone as a solvent and pentane as a precipitant, and the precipitates were titrated to determine the grafting ratio of MAH. The purified reaction products were also reacted with benzyl amine at 40{dollar}spcirc{dollar}C for 2 hr to verify PLA and MAH graft reaction.; NMR and FTIR testing results of the amidated products after purification showed evidence of the graft reaction. NMR and the titration results showed that the grafting ratio of MAH is approximately 0.5-2%. PLA reacted with 5%wt MAH (PLA-g-5MAH) also was extrusion blended with PEG (Mn = 10000). NMR analysis of the purified extrudate showed that the PLA and PEG graft copolymer was formed by reaction of PEG and appended MAH onto PLA.; From GPC testing results, it is seen that the molecular weight of the PLA-g-PEG is higher than that of PLA/PEG blends. The tensile property of the extrudate was tested and the results showed that this property of PLA/PEG was improved as compared to those of PLA/PEG physical blends. Enzymatic degradation test (protein K) results indicate that the degradation rate of graft copolymer was higher than that of pure PLA.