Nucleation effect of cellulose nanocrystals/polybutylene succinate composite filler on polylactic acid/polybutylene succinate blends

Polylactic acid (PLA)/polybutylene succinate (PBS) composites were prepared via melt blending PLA, PBS and a cellulose nanocrystal (CNC)/PBS composite filler. Polarizing light microscopy, isothermal crystallization, non-isothermal crystallization and wide-angle X-ray diffraction were employed to investigate the effects of the CNC/PBS composite on the crystallization behavior of the PLA/PBS blends. The addition of the CNC/PBS composite contributed to an increase in the thermal crystallization temperature of the PLA phase in the PLA/PBS blends, showing an enhancement of the crystallization ability of the PLA/PBS composites. The crystallization rate of pristine PLA had little change with increasing temperature in the range of 111-119 degrees C, while the crystallization completing time decreased to 1.3 min with 1% CNC addition, which was much shorter than that of pristine PLA, 2.6 min. The Avrami constant showed that the crystallization of pure PLA was mainly achieved by homogeneous nucleation, while the PLA phase of the PLA/PBS composites was due to heterogeneous nucleation. In addition, the crystallinity of the PLA phase in the composites increased after adding CNC/PBS filler with more particles and smaller particle size. With increased crystallinity and decreased crystal size especially in PLA component with increasing CNC/PBS filler content, both the Young's modulus and the flexural strength of the PLA/PBS composites thus increased. The tensile strength and impact strength had little change, indicating the flexibility of PLA/PBS was not weakened.