Enhancement of Polypropylene Bonding Through Plasma-Ultrasonic Treatment

In response to the issue of the insufficient adhesion strength of polypropylene materials, a plasma-ultrasonic treatment is proposed. Plasma treatment is first conducted to activate the polypropylene adherends, and then ultrasonic vibration is applied to the adhesive to facilitate the interface contact, enhancing the bonding performance of polypropylene. The shear strength of the test specimens was assessed using single-lap shear tests. The bonding samples were characterized by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS), contact angle, and infrared analysis to explore the bonding mechanism of plasma-ultrasonic treatment. The results show that compared to untreated polypropylene specimens, the plasma treatment process increased the shear strength of the polypropylene specimens by 370.3%, and the addition of ultrasonic-assisted technology further increased the shear strength of the polypropylene specimens by 10.6%. The coefficient of variation decreased from 0.53 in the untreated sample to 0.32 for the plasma-ultrasonic treatment, enhancing the stability of adhesion. Plasma treatment introduces active groups, such as hydroxyl groups, onto the surface of polypropylene and increases the surface roughness of polypropylene. Ultrasonic treatment promotes the penetration of adhesive microstructures on the surface of polypropylene, enhancing the anchoring effect of the adhesive, thereby improving bonding performance. Furthermore, through molecular dynamics analysis, compared to the untreated polypropylene bonding system, the bonding energy of the bonding system under the plasma-ultrasonic treatment was increased by 57%, effectively enhancing the shear strength of polypropylene bonding. Plasma-ultrasonic treatment can effectively improve the bonding strength of polypropylene, providing a new idea for the study of polymer bonding.