Effect of Hydrophobic Modification on Mechanical Properties of Chinese Fir Wood

The water repellency, elastic modulus, and hardness of hydrophobic-treated and untreated wood cell walls were investigated. Chinese fir (CF; Cunninghamia lanceolata (Lamb.) Hook) wood was modified using polydimethylsiloxane (PDMS) and dimethyldichlorosilane (DMDCS) dissolved in n-hexane at 2%, 5%, and 8% (w/w) for 5 min, 30 min, and 2 h, respectively. A hydrophobic property was observed in the modified wood. The water contact angle value of the untreated wood surface was 85°, but after treatment this value increased to 147° and 143° for the PDMS- and DMDCS-treated wood, respectively. Increases in the elastic modulus and hardness of the wood cell wall were observed after PDMS treatment. These treatments also improved the water repellency of the wood surface, as verified by the reduction of the hydroxyl group O-H stretching vibrations at 3328 cm-1. Compared to DMDCS, the PDMS treatment improved the hydrophobicity of wood surfaces and increased the nanomechanical properties of the wood cell wall. When an 8% concentration of PDMS and a 2 h treatment time were used, the treated wood showed the best mechanical properties.