Abstract:
The present work aims to improve poly(lactic acid) (PLA) toughness through practical approaches based on crystalline and amorphous phases optimization (i.e. nucleating agent and plasticizer additions and process conditions control). In case of nucleating agent addition, various silane modified starch were studied on both detailed structures and their effective functions for nucleation and compatibilization. Chloropropyl trimethoxysilane (CPMS) successfully formed covalent bonds with starch and PLA to produce the reactive PLA/CP- starch blend. This leads to the effective compatibility improvement as well as the significant increases of degree of crystallinity and chain mobility. This work is extended to produce PLA/modified thermoplastic starch film which performs the potential in use as mulch film. For applying of biaxial-stretching, the structural and thermal analyses under systematically varied stretching rates and draw ratios declare the relationship between PLA mechanical properties and PLA microstructure. When the high stretching rate combined with the high draw ratio (75 mm/s and 5x5). Many but small PLA crystals (8-crystallite) were created isotropically. It is the key factor for toughening PLA film. Furthermore. The present work also studies poly (L-lactic acid)-poly (L-lactic acid) (PLLA-PEG-PLLA) triblock copolymer with various PLLA chain length as miscible plasticizer. The difference in PLLA chain length has an effect on crystallization behavior of block copolymers. The recrystallization of PEG in PLA-PRG homopolymers blend could be evitable by using PLLA-PEG-PLLA to replace PEG. The miscibility between PLA/PLLA-PEG-PLLA was significantly enhanced while its toughness Was remained as high as that of PLA/PEG homopolymers blend.
