Enhanced crystallization of poly(lactic acid) bioplastics by a green and facile approach using liquid poly(ethylene glycol)
Polylactic acid (PLA) bioplastics have attracted increasing attention from both academic and industrial researchers due to their biomass?derived nature and low toxicity for the human body and environment. A major drawback of PLA is slow crystallization during processing, which considerably limits its commercial applications. In this study, a simple and low?cost approach involving the addition of eco?friendly low molecular weight poly(ethylene glycol) (PEG; 400?g/mole) as a green solvent was developed to enhance the PLA crystallization process. Differential scanning calorimetry and polarized optical microscopy data revealed that the introduction of PEG into PLA considerably increased the PLA crystallization rate. In particular, the isothermal crystallization rate of a system with a PLA/PEG mass ratio of 70/30 was more than seven times greater than that of neat PLA. In addition, the miscibility, thermal properties, and microstructures of various PLA/PEG blends were determined. A substantial reduction in the equilibrium melting temperature of PLA after PEG addition confirmed that these polymer blends were thermodynamically miscible in the melt, which strongly influenced the PLA crystallization rate. Furthermore, the addition of PEG increased the regularity of PLA crystals and induced the formation of ring?banded PLA spherulites with periodic twisted lamellae.