Experimental and numerical studies of polyamide 11 and 12 surfaces modified by atmospheric pressure plasma treatment

Polyamide 11 and 12 (PA11 and PA12) have been applicable in various industries, including automotive, oil and gas, and sporting goods, over the past 70 years. Although they have good dyeability, their adhesion to other materials is limited due to relatively poor surface properties, which can be promoted by good wettability and high surface energy. This study aims to improve the surface properties of PA11 and PA12 by employing the advanced method of Atmospheric Pressure Plasma Torch (APPT) treatment. In this regard, the adhesion strengths of four commercially available adhesives were evaluated with the pull-off test on PAs plates before and after APPT treatment. The numerical simulation of this test was carried out in commercial finite element software using a cohesive zone model (CZM) to predict the fracture of adhesively bonded joints. Moreover, the modified PAs were analyzed using XPS, DSC, ATR-FTIR, optical profilometer and surface energy measurement. The results indicated that the surface properties, including wettability, polar surface energy and adhesion bonding, improved by employing the plasma treatment on PAs surfaces. The numerical simulation outcomes showed that the pull-off test might be a viable alternative to determine the CZM laws for fracture mode I.