Enhanced crystallization of poly(lactic acid) bioplastics by a green and facile approach using liquid poly(ethylene glycol)

Abstract

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.

Green Polymer Electrolytes Prepared by a Cost-Effective Approach

“…Figure shows the photographs of PEG/PLLA with different weight compositions at room temperature. The melting temperatures of neat PEG (with a molecular weight of 400 g/mol) and PLLA are approximately 5.8 and 155 °C, respectively. , At room temperature, neat PEG exists in a liquid state. However, when PLLA is added, and the concentration reaches 30 wt % (PEG/PLLA 70/30), the sample undergoes a transition to a solid state, as indicated by the arrow in Figure .…”

“…This value is approximately seven times lower than that observed in neat PEG (400 g/mol) LPEs. The decrease in conductivity observed in PEG/PLLA 90/10 LPEs can be attributed to the presence of PLLA, where the crystallites of PLLA perturb the spatial continuity or distribution of the PEG phase (domain), significantly affecting the mobility of ion transport.…”

Crystallization improvement of PLA by the talc with “grafting from” method of polymerization of lactide

“…[9] . However, the low crystallinity, slow crystallization rate and low toughness of PLA limit its processing and application [10] , industrially accounting for a long injection-molding cycles [4,11] . Nowadays, the crystallinity of PLA has to be improved by blends or copolymers [12,13] , reinforcing with organic or inorganic llers during the process [14][15][16] , adjusting the molding parameters, such as cooling rate, time, and temperature.…”