Construction of high-efficiency fixing structure of waterborne paint on silicate-modified poplar surfaces by bridging with silane coupling agents

To improve the wettability, the surface free energy, and film adhesion performance of silicate-modified poplar wood (SMPW) surfaces, different silane coupling agents (KH550, KH560, KH570, and KH580) were applied to SMPW surfaces. The properties including film adhesion, functional groups, wettability, penetration depth, and surface free energy were analyzed and characterized by film adhesion tests, FT-IR, XPS, SEM, contact angle measurements, optical magnifying microscope test, and surface free energy calculations. The results showed that the film adhesion of poplar wood, SMPW, and the silane coupling agents KH550, KH560, KH570 and KH580 treated SMPW surfaces were grade 1, grade 3, grade 1, grade 0, grade 1, and grade 0, respectively. The SEM test results were consistent with results of the paint film adhesion. According to the XPS results, there were two binding energies peaks at 99–104 eV and 151–155 eV, corresponding to Si 2p and Si 2s, respectively, indicating that the form of Si had changed. In the FITR spectra, the SiOSi stretching and bending vibrations on the surface of the modified material treated with silane coupling agents were significantly stronger than that of the SMPW, indicating that silane coupling agents chemically bonded to the surface of the SMPW. The contact angles of the WBSV on the surface of poplar material, SMPW and silane coupling agent KH550, KH560, KH570, and KH580 were 50.60°, 77.17°, 52°, 45.92°, 52.83°, and 47.20°, respectively. The wettability of the surface after silicate modification was lower than that of the poplar material. After silane coupling agent treatment, the wettability of the surface to the WBSV was improved to varying degrees. The surface free energy of poplar and SMPW were 46.88 and 37.72 (10−3 J·m−2), respectively, illustrating that SMPW reduced the surface free energy. The surface free energy of SMPW treated with silane coupling agents KH550, KH560, KH570, and KH580 was 45.10, 50.93, 44.06, and 49.49 (10−3 J·m−2), respectively, which showed that the surface free energy of SMPW treated with different silane coupling agents was higher than that of SMPW.