Material PropertiesAnalysis of thermal properties and impact strength of PP/SRT, PP/EPDM and PP/SRT/EPDM mixtures in single screw extruder

Mixtures of ground scrap rubber tires (SRT) and polypropylene (PP); ethylene-propylene-diene terpolymer (EPDM) and PP; and, ground SRT, PP and EPDM were prepared using a single screw extruder. The temperatures of the five zones of the extruder were 190/200/200/210/220 °C and the screw speed was adjusted to 30 rpm. Impact strength and thermal properties were evaluated for all compositions. It was verified that the crystallization temperature (Tc), the degree of crystallinity (X%) and the heat of crystallization (ΔHc) decreased with increase of SRT or EPDM loading. For PP/SRT/EPDM compositions, the same or an intermediate effect was observed in the thermal properties according to the proportion SRT/EPDM. Impact strength did not show good improvement with SRT; however, in combination with EPDM (PP/SRT/EPDM 50/30/20 %w/w), an unexpected increase of PP impact strength was achieved.