Starch In Situ Grafting Lactide Study

The method of preparating starch-g-PLA copolymer by ring-opening polymerization of D, L-lactide and starch conducted in bulk was studied. Starch is a kind of polymer with abundant hydroxyl function groups. The ring-opening polymerization of lactide is initiated from the hydroxyl function groups to get starch-g-PLA copolymer. Starch was pre-gelatinized and plasticized in order to destroy the crystal structure and reduce the melting temperature. The structure of starch-g-PLA copolymer prepared by this method was proved by FTIR and NMR spectra.The method used poly(ethylene glycol) as the plasticizer of starch and stannous octanate(SnOct2) as the catalyst of the ring-opening polymerization. The polymerization was conducted in bulk and non-solvent condition.Starch-g-PLA copolymer had been prepared by ring-opening polymerization in solution. But the process of polymerization and purification need a lot of solvent, in addition this polymerization is more complex.In order to overcome these disadvantages, the graft polymerization of D, L-lactide and starch plasticized by poly(ethylene glycol) was conducted in bulk in our work. The effect of molecule weight and content of poly(ethylene glycol) on the graft efficiency was considered. The results showed that the chains of PLA were successfully grafted on starch.The compatibility of graft copolymer and PLA were also evaluated by the water tolerance and crystallinity of starch-g-PLA/PLLA blend. The results showed that the compatibility of graft copolymer with PLA was better than starch.