Effect of KH560 concentration on adhesion between silicate modified poplar and waterborne varnish

This paper describes the investigation of the effect of different concentrations of silane coupling agent KH560 (KH560) on the interface properties of silicate modified poplar wood (SMPW). These properties include the surface wettability, free energy, and film adhesion. With the exception of the film adhesion rating of SMPW treated with 0.5 % KH560 was grade 2, the film adhesion rating of SMPW treated with 1.0 %–3.0 % KH560 was grade 1. The SEM images showed that cracks between the waterborne (water-based polyurethane modified acrylic acid) varnish and SMPW gradually decreased upon increasing the KH560 concentration. The results of the FI-TR and XPS all indicated that the characteristic peak of Si-O-Si and the relative proportion of Si-O-Si groups were positively correlated with the concentration of KH560 in the treated SMPW. This indicates that KH560 was successfully grafted onto the substrate surface. After KH560 was combined with a water-based sealing primer (WBSP), the larger the concentration of KH560, the stronger the bond at 1730 cm−1. This means that the epoxy group in KH560 reacted with WBSP and was connected with the WBSP. After drenching the SMPW with the KH560 solution that had concentrations of 0.5 %, 1.5 %, and 2.5 %, the contact angles of WBSP on the substrate's surface were 62.55°, 60.10°, and 49.45°, respectively. The surface free energy of SMPW treated with 0.5 %, 1.5 %, and 2.5 % KH560 was 45.87, 49.55, and 50.29 (10−3 J·m−2), respectively. This indicated that increasing the KH560 concentration improved the wettability, increased the SMPW free energy value, and improved the film adhesion.