Preparation of stereocomplex-polylactide powder by precipitation method for potential use as nucleating agents in fully-biodegradable poly(L-lactide) composites

Abstract

In this work, low-molecular-weight poly(L-lactide)/poly(D-lactide) (LMW-PLLA/LMW-PDLA) blend solutions were precipitated as stereocomplex polylactide (scPLA) powders. The obtained scPLA powders with nearly spherical shape and particle sizes in the range of 104–610 nm showed complete stereocomplex formation and had a single melting-temperature at approximately 220 ˚C. The influence of the scPLA powder on the crystallization behavior of high-molecular-weight PLLA (HMW-PLLA) was elucidated. For this purpose, HMW-PLLA was melt blended with the scPLA powder. As investigated by non-isothermal-crystallization differential scanning calorimetry (DSC) analyses, the cold-crystallization temperature (T cc ) of HMW-PLLA upon DSC heating scans shifted to lower temperatures and the crystallization temperature (T c ) upon DSC cooling scans shifted to higher temperatures by the addition of the scPLA powder. The HMW-PLLA/scPLA powder composites exhibited a shorter half crystallization-time than pure HMW-PLLA for the isothermal-crystallization DSC analysis. The crystallinity content of HMW-PLLA/scPLA powder composites increased as the scPLA powder content increased, as revealed by X-ray diffractometry (XRD). The scPLA powders were well dispersed and had good phase-compatibility in the HMW-PLLA matrices, as determined by scanning electron microscopy (SEM). In conclusion, these fully biodegradable, non-toxic, and bio-based scPLA powders showed good potential for use as heterogeneous nucleating agents to improve the crystallization properties of PLLA bioplastic. • scPLA powders were prepared by a simple precipitation technique. • scPLA powders had nearly spherical in particle shape and showed complete stereocomplexation. • PLLA/scPLA powder bio-composites were prepared by melt blending. • scPLA powder acted as heterogeneous nucleating agents to improve PLLA crystallization.