Preparation and properties of silica sol/melamine glyoxal resin.

In this study, a composite modifier for wood impregnation is prepared, which is functional and environmentally friendly. The surface of silica sol was modified by using KH-560. The modified silica sol, melamine, and glyoxal were used as raw materials. The silica sol/melamine glyoxal resin (from now on referred to as Silica sol/MG) composite modifier was prepared based on in-situ polymerization. The physicochemical properties (viscosity, solid content and etc.) of the composite modifier were evaluated. The structural and thermal properties were characterized and analyzed by FTIR spectroscopy, particle size distribution, TG and DSC. The results showed that the viscosity and solid content of the composite modifier decreased with the increase in the mass of the silica sol. The FTIR spectroscopy showed peaks at 473 cm^-1 and 1101 cm^-1, which were assigned to bending and stretching vibrations of the Si-O-Si bond, respectively, indicating that the modified silica sol was successfully introduced into the MG resin. When the modified silica sol mass fraction was 30%-40%, the particle size distribution of the composite modifier was relatively uniform. TG analysis found that the thermal stability of the composite modifier was significantly improved compared with the unmodified resin. DSC analysis showed that adding the modified silica sol reduced the curing temperature of the modifier from 115.5 °C to 107.9 °C.