Mechanical and morphological properties of cellulose nanocrystal-polypropylene composites

In this work, the rheological, mechanical, morphological, and thermal properties of cellulose nanocrystal (CNC)-polypropylene (PP) composites prepared in the molten state were investigated. All samples contained a maleated PP used as combatibilizer. Degradation of the PP in the presence of CNCs at high processing temperature was shown to have a significant effect on the rheological behavior. For PPs with two different molecular weights and prepared at different temperatures, the tensile modulus of composites containing 2 wt% CNC was improved by about 30% and the tensile strength was increased up to 16%, in comparison with the unfilled matrices. The tensile strain at break of composites decreased by 17% up to 75% with respect to the matrix, depending on the processing conditions and PP used. Preparing the low molecular weight PP composites via twin-screw extrusion was shown to be more efficient than using an internal batch mixer. The tensile modulus of the PP/CNC composites could be fairly well described by a model proposed by Nielsen based on the Halpin-Tsai equation. Finally, properties of the PP/CNC composites have been compared to those of a PP reinforced with flax fibers and a PP filled with nanoclay. POLYM. COMPOS., 39:3605-3617, 2018. (c) 2017 Society of Plastics Engineers