Composites reinforced with reused tyres: Surface oxidant treatment to improve the interfacial compatibility

Reused tyres whose surfaces were treated with various chemical acids, such as H2SO4, HNO3 and HClO4, were used as reinforcement material in HDPE-reused tyre composites. Their mechanical properties (e.g. tensile strength, Young’s modulus, toughness and elongation at break) were studied to evaluate how surface treatments may improve compatibility between the two components. The effect of chemical modifications on the surface of reused tyres was monitored by FTIR, the determination of mechanical properties and SEM. The importance of rubber treatment can be assessed by comparing the results of treated and untreated composites with those for neat HDPE. Reused tyre rubber, added to the HDPE in small quantities, acts as a filler, improving the stiffness and providing a more brittle behaviour. Nevertheless, a rubber content above 10%, using either untreated rubber or rubber treated with HClO4, gives lower values of Young’s modulus than neat HDPE. Elongation and toughness values are also lower. Treatment with H2SO4 and HNO3 improves the ability of rubber to interact with the HDPE, increasing the material’s stiffness. The treatment with H2SO4 was the most effective, whereas HClO4 did not improve the material’s properties.