Enhanced crystallization kinetics of symmetric poly(l-lactide)/poly(d-lactide) stereocomplex in the presence of nanocrystalline cellulose

- Fully bio-based PLLA/PDLA/NCC blends with high sc-PLA content were prepared.
- Crystallization kinetics of sc-PLA was significantly enhanced by the addition of NCC.
- t1/2 of symmetric PLLA/PDLA blend decreased by ca. 78% at 180 °C after adding 0.5 wt% NCC.
- A deeper insight in the high nucleation efficiency of NCC on sc-PLA was provided.

In this work, poly(l-lactide)/poly(d-lactide)/nanocrystalline cellulose (PLLA/PDLA/NCC) stereocomplex blends were prepared using a solution blending method. The effect of NCC on the crystallization kinetics of symmetric PLLA/PDLA blend was systematically investigated. The incorporation of NCC significantly enhanced the formation of stereocomplex crystal (sc), as indicated by increasing the crystallization peak temperature and crystallinity of sc from approx. 143 °C and 24% to around 160 °C and 40%, respectively, during the non-isothermal crystallizing upon cooling at 10 °C/min. Meanwhile, the addition of NCC caused no influence on the crystal morphology and crystal form of sc in the PLLA/PDLA blend, as evidenced by the POM and WAXD results. The crystallization kinetics of the PLLA/PDLA/NCC blends was studied in detail by using the Dobreva and Gutzow model, the Avrami-Jeziorny equation and the well-known Avrami model. It was found that NCC showed high nucleating activity in the PLLA/PDLA blend. The half-life time of crystallization of the PLLA/PDLA blend was decreased by ca. 78% at 180 °C after the addition of 0.5 wt% NCC. In addition, POM tests showed that the nuclei density in the PLLA/PDLA blend during isothermally crystallizing at 180 °C was largely increased by the addition of NCC.