Influence of a nanoparticulate mineral filler addition and chemical modification of the mechanical properties and thermal aging of PU/Sisal composites

This work deals with filler hybridization effects, by the addition of a nanoparticulate mineral filler (bentonite), on the mechanical performance of compression molded Polyurethane/sisal composites with 25 wt % fiber content. Composite tensile and impact properties were evaluated as a function of mineral filler content (0-10 wt %) and chemical modifications. Thermal aging effects onf tensile (sigma, E, epsilon) properties of selected composites were also ascertained. The mineral filler (Brasgel PA sodium bentonite) was employed in the following forms: a) as received; b) treated with a 0,6N HCl solution; c) chemically modified with dodecyl dimethyl benzyl ammonium chloride (Dodigen) and d) chemically modified with cetyl trimethyl ammonium bromide (Cetremide). Our results show that bentonite addition increases the mechanical properties of PU/sisal composites and that best overall mechanical performances was achieved with addition of the hydrochloric acid trated mineral filler. Thermal aging for short times (up to 4 days) led to small increases in composite's elastic modulus na tensile strengths, which was attributed to post-curing of the matrix. Long thermal exposure (32 days) led to decreases in composite tensile properties (sigma, E, epsilon), which was attributed to oxidative degradation of both: matrix and sisal fibers. The most thermally resistant composite was the hybrid (PU/sisal-bentonite) whose mineral filler was chemically modified with Cetremide. DRX and SEM data indicate the hybrids with organofilized bentonites to be composed of micro and nanocomposite structures.

Poliurethane; nanoparticulate fillers; mechanical properties; thermal aging

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