Characterization of wood plastic composite based on HDPE and cashew nutshells processed in a thermokinetic mixer

Wood plastic composites (WPC), which are used in high-value markets, contribute to solve some of the problems associated with municipal solid waste accumulation. In this study, the effect of cashew nutshell powder (CNSP) content on properties of formulations with recycled high-density polyethylene, 5wt% of maleic anhydride grafted polypropylene and 5wt% of struktol TPW 113, a blend of complex, modified fatty acid ester, was evaluated. Mixtures containing from 20 to 60wt% CNSP were melt-processed, using a thermokinetic mixer. WPC's were characterized by differential scanning calorimetry, Fourier transform infrared spectroscopy, and melt flow index (MFI) measurements. Composite morphology and mechanical properties were also accessed, respectively, by scanning electron microscopy and tensile tests. Results show that the tensile strength of composites decreased as the content of CNSP increased due to poor reinforcement-matrix interface and voids formed during residual cashew nutshell liquid (CNSL) vaporization. On the other hand, elastic modulus decreased and elongation at break increased, both indicating a plasticizing effect of the residual CNSL, confirmed by crystallinity and MFI data. Differences in the thermal stability of composites were restricted to thermal behavior of main components. POLYM. COMPOS., 39:2662-2673, 2018. (c) 2016 Society of Plastics Engineers