Influence of rubber particle size on properties of recycled thermoplastics containing rubber tyre waste

Abstract

Recycling represents a valid alternative to the disposal of post-consumer plastics in common landfills only when it is possible to obtain new materials with good final properties through practical applications and above all using inexpensive methods. Considering the problem of the great amount of rubber tyre waste produced worldwide, the objectives of this study are to incorporate particles of tyre rubber (TR) waste scrap into a thermoplastic matrix, post-consumer polypropylene (PP) and high impact polystyrene (HIPS) and to evaluate the rheological, physical and mechanical properties. The thermoplastic materials used were ground, washed, dried and ground again into flake form. The particle sizes of the TR used were <500 and 500–1000 μm, separated using a system of sieves of the Tyler mesh series. The PP/TR and HIPS/TR composites, both with weight ratios of 90∶10 and 70∶30, were processed by injection moulding. Results for the rheological behaviour showed that the incorporation of TR particles into the recycled HIPS and PP matrix led to opposite behaviours and that the extent of the effect was dependent on the nature of the polymer and the filler type and particle size. In addition, the presence and concentration of TR led to a reduction in the mechanical properties when compared with the unfilled matrix (post-consumer PP and HIPS), as confirmed by SEM images and the physical properties.