Crystallization Behaviors of Poly (Lactic Acid) Modified with ST-NAB3 and Its Improved Mechanical and Thermal Properties

Biodegradable poly (lactic acid) (PLA) as a great substitute for petroleum-based plastics was widely used to reduce environmental pollution resulted by greenhouse gas emissions. However, the practical application range of PLA was limited due to the inherently poor crystallization, mechanical and heat resistance properties. In this context, a heterogeneous nucleating agent (HNA) was incorporated into PLA matrix to address the problems mentioned above. The effects of HNA on the crystallization kinetics of PLA were explored by Avrami method. Isothermal and nonisothermal crystallization kinetics of PLA/HNA systems containing various HNA contents (0-0.75 wt.%) proved that HNA could generate the heterogeneous nucleation of PLA matrix and effectively improve its crystallization rates. The t(1/2) of PLA/HNA-0.75 composite decreased to 2.35 min compared with 34.12 min for pure PLA at isothermal temperature of 135 degrees C. The crystallinity of PLA/HNA-0.75 composite was enhanced by 42.1% in contrast with pure PLA. The shish-kebab structure of PLA/HNA composites containing various HNA contents (0.25-0.75 wt.%) was observed by polarized optical microscope as the concentration of HNA exceeded 0.375 wt.%. PLA/HNA-0.75 composite possessed the highest unnotched izod impact strength (33.6 kJ/m(2)), notched izod impact strength (4.3 kJ/m(2)) and heat deformation temperature (73.2 degrees C). In general, a feasible method was proposed for preparation of PLA with excellent mechanical and heat resistance properties through this work.

Automated summary

Biodegradable poly (lactic acid) (PLA) is widely used as a substitute for petroleum-based plastics to reduce environmental pollution. However, its practical application is limited due to poor crystallization, mechanical and heat resistance properties. To address these issues, a heterogeneous nucleating agent (HNA) was incorporated into PLA matrix, which significantly improved its crystallization rates and mechanical properties. This study provides a feasible method for preparing PLA with excellent mechanical and heat resistance properties.