Direct preparation of poly(L-lactic acid) by ring-opening polymerization of L-lactide using a twin-screw extruder

The poly(L-lactic acid)(PLLA) was rapidly synthesized from L-lactide(L-LA) by using 2-ethylhexanoic acid tin(II) salt and triphenylphosphine as the catalyst system and using a twin-screw extruder as a reactor.The effects of the polymerization time,polymerization temperature,the screw speed and the catalyst content on polymer properties were investigated.The results showed that when the twin-screw speed was 110 r/min,the polymerization temperature was 170 ℃,the molar ratio of monomer/catalyst was 2 000:1 and the polymerization time was 1.5 h,the PLLA polymer with a molecular weight of about 49 000 and optical purity of 93% could be obtained.