Studies on the effect of polylactide in-situ grafting during melt processing on poly(ʟ-lactide)/graphene oxide composite films.

The present work tried to solve the compatibility and dispersion problems of industrial grade graphene oxide (GO) mixing with polylactide (PLA) by melt processing for practical application. PLA was grafted on the GO using the silane coupling agent (KH560) as "bridge" by in-situ melting reaction to improve the compatibility. For better compatibility and dispersion, poly(ᴅ-lactide) (PDLA) was grafted on GO (D-G) to form stereocomplex crystallites with poly(ʟ-lactide) (PLLA) to enhance the interaction between GO and PLLA matrix. By biaxial stretching, the PLLA and GO composite films were prepared. Results show that GO was seriously aggregated in the film containing GO without PLA grafting (PLLA/L/G) and the average size of aggregated GO was about 19.5 μm. PLA grafting decreased the aggregated GO size, so that the films containing L-G or D-G presented better dispersion. The film containing 5 % D-G (PLLA/D-G) exhibited the smallest average size of aggregated GO, about 12.7 μm. Compared with neat PLLA film, PLLA/L/G film presented worse tensile properties due to serious aggregation of GO. While, PLLA/D-G film presented the best tensile performance that tensile strength and elongation at break reached 120 MPa and 107 %, respectively.