Chain heterogeneity of poly(lactic acid) and its influence on crystallization kinetics

Temperature rising elution fractionation (TREF) approach was used to separate a biodegradable poly(lactic acid) (PLA) resin into ten fractions and completely establish the relationship between chain microstructure and properties. The main fractions were mainly eluted at 100, 110, 114, and 118 °C, and their mass percentages were 7.98 wt%, 44.83 wt%, 19.64 wt%, and 11.90 wt%, respectively. Through the use of successive self-nucleation/annealing (SSA) thermal fractionation, gel permeation chromatography (GPC), differential scanning calorimetry (DSC), and ¹³C-nuclear magnetic resonance spectroscopy (¹³C NMR), the intermolecular and intramolecular differences of PLA were further explored. Fractions eluted at 90, 110, 118, and 126 °C were also chosen to research the non-isothermal cold crystallization kinetics, and fractions eluted at 110, 118, and 126 °C were chosen to explore the non-isothermal crystallization kinetics in order to simulate the real process. The findings demonstrated that the Liu-Mo approach were more suited the non-isothermal crystallization and non-isothermal cold crystallization kinetics of PLA. As the elution temperature increased, so did the stereoregularity of the fractions, the crystallization rate, the crystallization capacity, and the lamellar thickness. These will lay a foundation for its basic research and industrial application.