Mechanical Properties of Recycled Polypropylene/SBR Rubber Crumbs Blends Reinforced by Birch Wood Flour

In this work, recycled polypropylene (PP) and regenerated styrene butadiene rubber (SBR) from used tyres rubber crumbs were combined to produce polymeric blends. The compounds were prepared via twin-screw extrusion to measure their mechanical behaviour for different SBR compositions (0 to 40%). Also, the addition of birch flour (0 to 40%) and coupling agent (0 to 5 phr) content were studied. The results showed that tensile strength and modulus of the blends were substantially improved after incorporation of wood flour. The torsion modulus also increased with birch content. However, the tensile strain at break of PP/birch wood composites decreased with both wood and coupling agent contents, showing a decrease in ductility of the composites. Adding the elastomer phase did not improve the properties. The results showed that adding a coupling agent was found to be effective in improving the wood flour-PP interface, while less improvement was observed for the rubber-PP surface adhesion. The tensile strength of PP/birch composites improved by more than 60%, while the torsion and tensile moduli of the composites improved by only 10% in some cases.