The Study on the Grafting of Glycidyl Methacrylate onto Poly(lactic acid) in an Internal Mixer

Abstract

Glycidyl methacrylate (GMA) was grafted onto poly(lactic acid) (PLA) by melt mixing in an internal mixer using dicumyl peroxide (DCP) as an initiator. The results from nuclear magnetic resonance (¹H-NMR) and Fourier transform infrared (FTIR) spectroscopy indicated that the grafting reaction of GMA onto PLA took place successfully. After grafting, the brittle behaviour of PLA was changed to ductile behaviour of glycidyl methacrylate grafted poly(lactic acid) (PLA-g-GMA). The elongation at break and impact strength of PLA-g-GMA were significantly higher than those of pure PLA. In order to obtain the optimal mixing conditions, the mixing time was varied from 7, 10 to 14 min. PLA-g-GMA prepared by mixing for 10 and 14 min showed melt crystallization upon cooling. This was different from PLA and PLA-g-GMA prepared by mixing for 7 min, which did not undergo crystallization upon cooling from the melt. A mixing time of 10 min was found to give the optimum grafting yield, elongation at break and impact strength of PLA-g-GMA. With the significantly improved mechanical properties compared to those of pure PLA, the new, biodegradable PLA-g-GMA obtained from this study can be used to replace pristine PLA which has many drawbacks in many industrial applications.