Glycidyl Methacrylate Grafted Polylactic Acid: Morphological Properties and Crystallization Behavior

In this study, physical properties of glycidyl methacrylate grafted polylactic acid (PLA-g-GMA) were studied and compared with those of polylactic acid (PLA). PLA-g-GMA was prepared by using an internal mixer. Differences in crystallization characteristics between PLA-g-GMA and PLA were observed from X-ray diffraction (XRD). After applying tensile stress to PLA-g-GMA and PLA samples, diffraction peak (2u) at about 29 degrees was clearly occurred only in PLA-g-GMA samples. This implies that small crystals may be formed during applying tensile stress to PLA-g-GMA. The stress-strain curve of PLA-g-GMA exhibits necking and cold drawing characteristic which was not observed in PLA. Fracture behavior in the tensile test changed from the brittle fracture of neat PLA to the ductile fracture of PLA-g-GMA. Fibrillar structure of PLA-g-GMA from tensile fractured surface were observed by scanning electron microscope (SEM). In contrast, PLA did not show fibrillar structure from SEM micrographs. From differential scanning calorimetry (DSC), PLA-g-GMA shows lower glass transition temperature (T-g) and crystallization temperature (T-c) than PLA. Melt crystallization during cooling was observed only from PLA-g-GMA. Moreover, PLA-g-GMA showed only one melting peak while PLA showed two melting peaks. This indicated different types of crystal forms between PLA-g-GMA and PLA. Crystal forms in PLA-g-GMA may be less perfect and can be rearranged due to higher chain flexibility during tensile stress. Thus, significantly higher elongation at break of PLA-g-GMA was obtained compared to that of PLA.