Wood treatment was conducted by paraffin/acrylate compound emulsion. Response surface methodology (RSM) was applied for modeling and to determine the relationship between hydrophobicity and influencing factors. The results showed that the paraffin emulsion concentration and acrylate emulsion percentage had significant influences on water absorption (WA) and mass percentage gain (MG). The WA decreased obviously with increasing acrylate emulsion percentage. The correlation models for WA and MG showed a good prediction due to the straight-line distribution in the normal probability plot of residuals. The optimal conditions (5.57% paraffin emulsion concentration, 20% acrylate emulsion percentage, and 10 min treatment time) provided by RSM were acceptable for predicting the MG and WA. Compared to untreated (66°) and paraffin emulsion treated wood (94°), the wood treated by compound emulsion showed the highest water contact angle (133°) and better dimensional stability. This could be ascribed to a synergistic effect (bulking effect and filling effect) provided by paraffin and acrylate, which could form a completely hydrophobic film in wood.

Thermal modification could act as pretreatment for promoting silica sol impregnation in wood. It could create extra available channels and spaces for silica transportation and deposition owing to the presence of micro-cracks and enlarged pore size. The significant improvements on anti-hygroscopicity, hydrophobicity, and dimensional stability of treated wood were attributed to the degradation of cell wall polymer (hemicellulose, cellulose, and lignin) and filling effect of silica in wood. The synergistic effect contained the reduction on –OH concentration owing to thermal degradation, and consumption of –OH groups via the interaction (Si–O–Si cross linked networks and Si–O–C covalent bonds) between silica and wood matrix. Furthermore, the degradation of cell wall polymers resulted in the increase of crystallinity in wood. However, the crystallinity turned to decrease due to the amorphous silica impregnation. The silica impregnation could compensate the mass loss caused by thermal degradation, leading to various weight percentage gains (WPGs) that depended on treatment temperature. Moreover, owing to the coverage and penetration of mineral silica in wood, acting as a thermal barrier, the thermal stability and surface hardness of treated wood improved prominently.

Based on the results of nitrogen adsorption and dynamic vapour sorption as well as analysis by the Hailwood–Horrobin (H-H) model, the effects of γ-methacryloxypropyltrimethoxysilane (MPTS) on the agglomeration and moisture sorption properties of fumed silica particles were investigated. After adding various concentrations (2%, 4%, 6% and 8%) of MPTS, different degrees of silanization were obtained by showing various ─OH group contents on the silica surface, which resulted in silica agglomerates with different porous structures. The bigger mesopores in the unmodified silica agglomerates became smaller and finally disappeared after MPTS modification and the Bruanuer–Emmett–Teller surface area decreased more gradually with an increase in MPTS concentration. The H-H model fitted the sorption isotherms very well, and both hydrated water and dissolved water showed decreasing trends with the increase in MPTS concentration, showing reduced hygroscopicity. Up to 6% MPTS, the ─OH groups decreased with increasing MPTS concentration, as indicated by reduced K _h and W parameters, while at 8% MPTS an extensive self-condensation of MPTS occurred. Adsorption hysteresis appeared for moisture sorption on silanized silica, especially at low relative humidity values and at low MPTS concentrations, which could be explained by a synergistic effect of the surface ─OH group content and pore characteristics. These results could aid our understanding of the applications of silane-modified silica particles.