Rheological, mechanical, thermal and electrical properties of UHMWPE/CNC composites

In this work, composites of ultra high molecular weight polyethylene (UHMWPE) and various loadings of cellulose nanocrystals (CNCs) were prepared exploiting different methods. Besides, the microstructure, rheological, mechanical, thermal and electrical properties of the obtained materials were thoroughly investigated. As far as the mechanical behavior of the formulated systems is concerned, CNC-reinforced composites exhibited improved values of Young’s modulus and yielding strength with respect to the unfilled UHMWPE. In particular, the maximum value of ultimate tensile strength was achieved for the systems containing 0.1 wt% of CNCs, and then progressively decreased with increasing the particle loading. As assessed by XRD and DSC analyses, CNC-containing composites showed higher crystallinity degree as compared to the unfilled UHMWPE, suggesting a nucleating effect of embedded CNCs. Morphological and rheological analyses demonstrated that the preparation method involving a solution mixing step is more effective than dry method in promoting the achievement of a peculiar morphology, in which the embedded particles are preferentially located in the interfacial region between UHMWPE grains. Finally, electrical and thermal measurements documented that UHMWPE/CNC composites obtained by solution mixing showed slightly higher thermal conductivity and lower volume resistivity in comparison with the composites prepared by dry method, highlighting that the proper selection of the processing method plays a key role in determining the material final performances.