Comparative study of different aminosilane coupling agents for modification of carbon fibers/waste paper fiber/polyvinyl alcohol composite films

Abstract

Silane coupling agents graft onto carbon fibers (CF), enhancing the interfacial bonding between CF and the substrate. The number of alkoxyl groups in the aminosilane coupling agent influences the formation of siloxane networks, while the amine groups exhibit strong polarity, which catalyze the hydrolysis of alkoxyl groups and promote grafting onto CF. In this study, KH-540, KH-602, and KH-792 aminosilane coupling agents were each used to modify CF at concentrations of 1 wt%, 2 wt%, and 3 wt%. CF/waste paper fiber/polyvinyl alcohol composite films were prepared both before and after modification. KH-540 is a monoamino-trialkoxy type, KH-602 is a bis-amino-bis-alkoxy type, and KH-792 is a bis-amino-trialkoxy type. X-ray spectroscopy characterization revealed that the grafting rate of CF followed the order: KH-540 > KH-602 > KH-792. Scanning electron microscopy (SEM) and water contact angle measurements confirmed the formation of a silane network on the CF surface, with the water contact angle of modified CF decreasing compared to that of sulfuric acid-treated CF. The optimal electrical conductivity and tensile strength were observed in composite films modified with 2 wt% of each KH-540, KH-602, and KH-792, with the highest conductivity (252.5 S/m) achieved in the 2 wt% KH-540-modified film. This study explores the modification mechanism of CF using aminosilane coupling agents and their effects on enhancing composite film properties, providing a valuable reference for future research on CF modification with such agents.