The effects of cellulose nanocrystal and dicumyl peroxide on the crystallization kinetics of polylactic acid

Cellulose nanocrystals (CNCs) have been blended into polylactic acid (PLA) to improve the polymer's properties. The dispersion of CNC in the matrix has a strong influence on the properties of the nanocomposites. In this study, PLA and CNC were compounded by a reactive extrusion process using dicarbonyl peroxide (DCP) as the free radical initiator. Isothermal and non-isothermal crystallization kinetics of the resulting nanocomposites were investigated to understand the effect of PLA-D-CNC on the crystallization of the materials. Nuclear magnetic resonance and Fourier transform infrared spectroscopy analyses confirmed the grafting of PLA onto CNC via reactive extrusion. The Avrami and Tobin model studies showed that the reactive extrusion product PLA-D-CNC exhibited much higher crystallization rates compared to neat PLA, PLA/CNC (without DCP), and PLA/DCP. The maximum crystallization rate temperature of PLA, PLA/CNC, and PLA/DCP was increased from similar to 100 to similar to 110 degrees C for PLA-D-CNC. The results showed that CNC promoted PLA nucleation and crystallization at high temperatures under the action of DCP. Specifically, the maximum crystallization rate of PLA-D-CNC was 46 times higher than that of neat PLA. PLA-D-CNC showed a two-stage crystallization process, while the other three samples exhibited mostly single-stage processes. The much-enhanced crystallization of PLA-D-CNC was ascribed to the improved interaction between PLA and PLA-D-CNC and the homogeneous dispersion of CNC.