Effect of oligolactic acid stereocomplex microplates as rapid crystallization nucleating agents on the properties of poly(L-lactic acid)

An efficient and scalable method to prepare oligolactic acid stereocomplex microplates (SC-OLA-MPs) is developed. Oligolactic acid was firstly synthesized via the melt polycondensation of lactic acid. Then, the oligo ( L -lactic acid) and oligo ( D -lactic acid) were crystallized with a mixture of dichloromethane and acetone, and consequently the stereocomplex microparticles were obtained in the form of circular microplates with a diameter of approximately 2 μm. As an eco-friendly nucleating agent, SC-OLA-MPs were introduced into poly ( L -lactic acid) (PLLA) via melt blending. The nonisothermal and isothermal crystallization of the SC-OLA-MPs/PLLA composites were investigated, and the crystal morphology and heterogeneous nucleation phenomena during the isothermal crystallization process were photographed with POM. SC-OLA-MPs show excellent nucleating effects on PLLA crystallization. With the incorporation of 10% SC-OLA-MPs, the crystallization half-time of the SC-OLA-MPs/PLLA composite decreased from 7.18 to 0.45 min at 100°C, compared to the neat PLLA. Through a short-time molding procedure, the thermal deformation temperature of PLLA is improved by the addition of SC-OLA-MPs. Highlights Polylactic acid stereocomplex microplates were fabricated by solution crystallization. This method is easy and scalable. This microplate is an effective nucleating agent for PLLA.