Investigation of Polyethylene/Sisal Whiskers Nanocomposites Prepared Under Different Conditions

In this work, sisal nanowhiskers (SNWs) extracted from sisal fibers were used to reinforce high-density polyethylene (HDPE) and low-density polyethylene (LDPE). The nanocomposites were prepared by solution casting from toluene and melt mixing, both followed by melt pressing. In the case of melt mixing, the surfaces of the SNW were also chemically modified with 1 phr of vinyl triethoxy silane to improve their dispersibility and compatibility with the matrices. The SNW had an average length of 197 nm and diameter of 12 nm, and a crystallinity index of 89%. Fourier transform infrared confirmed the surface chemical modification of the SNW. The whiskers were fairly well dispersed in the matrices, regardless of the treatment or preparation method. The presence of whiskers, as well as nanocomposite preparation method, had an observable influence on the storage modulus of LDPE, but very little influence on that of HDPE. There was, however, no significant influence on the degradation behavior of both polymers. The crystallization behavior of the polymers was found to strongly depend on their morphologies. The melting and crystallization behavior of the LDPE nanocomposites were almost unchanged, while an increase in crystallinity was observed for all the HDPE nanocomposites. The tensile properties depended on the type of polymer, the treatment, and the preparation method. Generally there was an improvement in tensile modulus, and a decrease in elongation at break, but the stress at break only improved for the HDPE nanocomposites. (C) 2014 Society of Plastics Engineers