Ultrasonic welding of ground tire rubber-filled polypropylene blends

• We studied the weldability of polypropylene-based thermoplastic elastomers containing ground tire rubber. • All materials produced high-quality welds without cracks or voids. • The blends displayed damping properties similar to polypropylene, ensuring weldability. • Ultrasonic load degrades the rubber filler, enhancing its ability to connect. In this study, we examined the weldability of thermoplastic elastomers made from ground tire rubber (GTR) with polypropylene and explored the effects of devulcanized GTR (dGTR) and dynamic vulcanization to produce thermoplastic dynamic vulcanizates (TDV). We characterized the damping properties of blends and revulcanized dGTR and found that increasing load does not affect the damping of the rubber, but the blends behaved similarly to polypropylene. We examined the effect of welding force and time on welds between polypropylene and the blends and found that both time and force have an optimum for the best maximum force and elongation: the best properties were examined with 0.3 s of weld time and 200 N of weld force. Similar trends were observed in welds between identical blend types. We also examined the morphology of the seams and found that both devulcanization and dynamic vulcanization helped to distribute the rubber phase better, which resulted in seams with smaller rubber particles that can act as defects. We used Taguchi analysis to determine that the TDV provided seams with PP with the best quality at 300 N of weld force. We also showed that no specimen exhibited voids and cracks in the seam. Our findings show that filling GTR or dGTR in polypropylene results in a rubber-like thermoplastic material which is also characterized by good weldability. This article shows an application of inserting GTR into circular economy.