Microwave Welding of Polypropylene Using SiC Nanowires as Susceptors: Effect of Silane Modification on Joint Performance

Abstract A reinforced silicon carbide nanowires/polypropylene (SiCNWs/PP) nanocomposite welded joint was successfully fabricated using microwave welding. To improve compatibility between hydrophilic SiCNWs and hydrophobic PP, silane coupling agents were employed for surface modification, leveraging their amphiphilic properties. Vinyltriethoxysilane (VTES) and γ-methacryloxypropyltrimethoxysilane (KH570) were selected as surface modifiers, with Fourier-transform infrared spectroscopy confirming the successful grafting of vinyl and methacryloxy groups onto SiCNWs. Incorporating 1 wt% VTES- and KH570-modified SiCNWs significantly enhanced the mechanical performance of the welded joints, improving tensile strength, flexural strength, and modulus of elasticity. The tensile strengths of joints with 1 wt% VTES- and KH570-modified SiCNWs reached 2.45 MPa and 2.83 MPa, respectively, surpassing the 2.21 MPa recorded for joints with unmodified SiCNWs. Flexural strength also improved substantially, increasing by 123.43% and 201.86% for 1 wt% VTES- and KH570-modified SiCNWs, respectively, compared to approximately 7 MPa for unmodified SiCNWs. Notably, joints with 1 wt% KH570-modified SiCNWs exhibited superior mechanical properties compared to VTES-modified joints, attributed to the higher hydrophobicity of the methacryloxy group. However, increasing the concentration of silane coupling agents to 3 wt% led to a decline in mechanical performance, likely due to insufficient microwave absorption and incomplete weld formation. The tensile strengths of joints with 3 wt% VTES- and KH570-modified SiCNWs decreased to 2.25 MPa and 2.69 MPa, respectively. This study highlights the potential of silane-modified SiCNWs for fabricating high-strength nanocomposite joints via microwave welding, providing valuable insights into the advancement of thermoplastic joining technologies. Graphical Abstract