Effect of Waste Tire Dust (WTD) Size on the Mechanical and Morphological Properties of Polypropylene/Waste Tire Dust (PP/WTD) Blends

Waste tire dust (WTD) of mechanically reclaimed scrap tires was blended with polypropylene (PP) in five different compositions to prepare PP/WTD blends. Three series of blends with three different sizes of WTD (250–500 µm, 500–710 µm, and 710 µm–1 mm) were prepared in a Haake Rheomix Polydrive R 600/610 at a temperature of 180°C and a rotor speed of 50 rpm for 9 min. The results show that at the same blending composition, the PP/WTD blends with fine WTD size require higher equilibrium torque and exhibit higher values of tensile strength, Young's modulus, and elongation at break (Eb) than that of blends with coarser WTD size. The swelling index of the PP/WTD blends reveals that the blends with fine WTD size have better swelling resistance in both oil and toluene than all blends with coarser WTD. Scanning electron microscope (SEM) observation indicates that the PP/WTD blends with the finest WTD size exhibit better PP/WTD adhesion than blends with coarse WTD sizes.