A simple method to enhance the interface properties of carbon fibre/polyamide 6 composites: Grafted caprolactam-blocked 3-isocyanatopropyltriethoxysilane on carbon fibre surface

Abstract

Introducing the isocyanate group on the carbon fibre (CF) to improve surface activity is an effective modification method. Still, its application in the industrial field is restricted because the modification process is harmful to the environment and isocyanate is easy to fail. In this paper, 3-isocyanopropyltriethoxysilane (IPTS) has been blocked with caprolactam (CPL) have been prepared. By adjusting the hydrolysis conditions and concentration of the modified coupling agent solution, the CPL-blocked IPTS was grafted to the surface oxidized CF, and the CF-reinforced polyamide 6 (PA6) composites were prepared. After treating CF with 1.0wt% coupling agent solution, the composites’ interlaminar shear strength (ILSS) reached 52.53 MPa, which was 23.83% greater than that of the desized CF/PA6 composites. High-temperature composite molding caused CPL-blocked IPTS to unblock, and the isocyanate that was released thermally intereacted with the terminal amino group of PA6 to establish a high strength interface through covalent grafting, which was the main reason for improving ILSS. This study indicates that this method is safe and simple and can effectively improve the interface properties of CF/PA6 composites.