Effects of filler treatments on the mechanical and morphological behavior of PP plus wood flour and PP plus sisal fiber

Composites were prepared from waste wood flour, sisal fiber and polypropyle ne (PP). The surface of the filler was modified to enhance the chemical aff inity between hydrophilic cellulosic and hydrophobic polymer. The treatment s studied were: a) The addition of a coupling agent; b) chemical treatment with NaOH; and c) the addition of functionalized polypropylene (Poly-bond 3 150 and 3200). After treatment, mixtures of PP with 40% and 20% of the fill er, wood flour and sisal fiber respectively, were extruded and injection mo lded. In the case of wood flour, a mixture of two particle sizes (mesh 20 a nd 40, 50% each) was used, and in the case of sisal, 10 mm long fibers were selected. Results showed that, regardless of the treatment to which the fi ller was previously submitted, Young's modulus was always higher for mixtur es prepared with wood flour, with values varying between 2839 and 3150 MPa. Whereas for mixtures with sisal fiber, the modulus' values varied between 1704 and 2220 MPa. Values of breaking strength, elongation at break and imp act strength for PP mixtures with treated sisal fiber were always higher th an those for mixtures of PP with wood flour. Based on these results, we can conclude that sisal fiber is an organic filler which, due to its mechanica l and morphological characteristics, has a reinforcing effect higher than t hat of wood flour.