Polypropylene surface modification by low pressure plasma to increase adhesive bonding: Effect of process parameters

The purpose of this study is to evaluate the effect of a cold plasma surface treatment of polypropylene substrates with the aim of increasing their adhesion characteristics. These substrates were treated with plasma, using different process parameters such as power, time and working gas. The effect of the treatment has been studied through a surface characterization, analyzing the chemical species created on the topmost layer of the substrates thanks to the plasma treatment and evaluating the surface energy, through contact angle measurements. Then, untreated and plasma treated samples with various parameters were used to create single overlapping bonded joints and evaluate the effect of the surface treatment on the mechanical characteristics of the joints. Experimental results show that plasma treatment is an effective treatment for the surface preparation of polypropylene adhesive bonding. In fact, the increase in surface energy and the formation of chemical bonds between oxygen and carbon have favored the adhesion, thus increasing the mechanical strength of the joint.