Highly crystallized poly (lactic acid) under high pressure

Biodegradable poly (lactic acid) (PLA) usually has a crystallinity less than 10% due to its poor crystallization ability. In this work, we found high pressure could significantly facilitate formation of crystallites of PLA, resulting in a crystallinity high up to 66.3% at pressure and temperature of 300 MPa and 185 oC. High-pressure induced crystalline reorganization and lamellar thickening led to two melting temperatures in the highly crystallized PLA but without cold crystallization compared to the normal-pressure crystallized PLA. Temperature dependence of high-pressure crystallization of PLA suggested desirable crystallization temperatures for highly crystallized PLA products.