Thermoplastic elastomers based on polypropylene: Effects of waste tire rubber and gamma radiation on mechanical properties

Tire rubber has always been a major environmental and waste management problem due to its non-biodegradability and accumulation in landfills. Moreover, global statistics reveal that a substantial number of tires become unsuitable for use or retreading. For the reasons, in this work waste tire rubber was used to produce thermoplastic elastomers. The work consisted of three experimental stages. In the first one, the contribution of the tire rubber sizes was evaluated in thermoplastics with 80% polypropylene and 20% waste tire rubber, having sizes of 180, 250, 420, 850 and 2000 μm. The best results were obtained for thermoplastics with waste tire rubber of 250 μm, showing improvements in the tensile and flexural strength as well as in the Izod impact. In the second stage, the contribution of the content of tire rubber was evaluated, having concentrations from 10% to 50% of tire rubber. The results show increase in the tensile strain and Izod impact. Finally, in the third stage, the exposition to gamma radiation of the thermoplastics was evaluated, having irradiation doses from 100 to 500 kGy. The thermoplastics were produced with 60% PP and 40% waste tire particles. The results show increase in flexural strength and the modulus of elasticity (in tensile and flexural) with the radiation dose increases. The use of waste tire rubber and the treatment by gamma radiation offers an option for improvement mechanical properties of thermoplastic elastomers.