Enhanced interfacial bonding strength between metal and polymer via synergistic effects of particle anchoring and chemical bonding

Abstract To enhance the performance of metal-polymer joint, surface modification is normally applied. Different from the common methods of increasing roughness or manufacturing complicated patterning, a new strategy of microscale morphology design of low roughness surface was introduced in this work, for improving the interfacial bonding strength between Ti6Al4V titanium alloy (TC4) and polyethylene terephthalate (PET) joined by hot pressing method. Low-roughness (Ra = 0.18 μm) surface achieved by HF etching can also significantly enhance the interfacial bonding strength of TC4-PET joint by 133%, from 4.5 MPa (as-polished) to 10.5 MPa, as high as the joint strength achieved by sandblasting (11 MPa) with much higher roughness (Ra = 3.7 μm). The bonding mechanisms in joints with different surface treatments were investigated and compared, showing that a new effect of surface particle anchoring played a key role in enhancing the interfacial bonding. Based on the characterization results and analyses, the crack propagation paths of HF and HNO3-HF treated samples were clarified and illustrated. This study indicated that roughness is not the only decisive factor of joint strength and demonstrated a new effective strategy via synergistic effects of surface particle anchoring and chemical bonding to improve interfacial bonding of metal and polymer from both theoretical and practical points of view.