Enhancing welding strength of thermoplastic vulcanizate/aluminum alloy via adding zinc methacrylate

Abstract

Welding of metals and polymer materials has always been one of the difficult problems. In this work, we incorporated zinc methacrylate (ZDMA) to polypropylene/ethylene propylene diene rubber thermoplastic vulcanizate (PP/EPDM TPV) to improve the welding performance of the TPV and A6061-t6 aluminum alloy (6061). We firstly processed a welding simulation experiment on a flat vulcanizer. In the experiment of simulating heat source, ZDMA effectively improved the strength of TPV/6061 joints, and the strength of the joints with 30 phr (parts per hundreds of rubber) ZDMA increased tenfold compared to that with 5 phr ZDMA. The increase of joint strength was the result of the combined effect of TPV's polarity, dimensional stability, and interfacial chemical bonds. The results of X-ray photoelectron spectroscopy (XPS) and scanning electron microscope (SEM) showed that: during the welding process, the carboxylate ions (-COO-) of ZDMA in TPV migrated to the interface of TPV/6061 joints and constructed chemical bonds (C–O–Al) with 6061. Then, we welded the TPV and 6061 using a Friction Stir Spot Welding (FSSW) machine, the strong interface strength (tension-shear load = 1.2 kN) between TPV and 6061 verified our simulation experiment. Furthermore, the knowledge in this work will benefit the research in welding of TPV and lightweight metals to improve the strength of the interface between plastics and metals.