Functional modification of hydrophobicity and oleophobicity for wood surface of Pinus kesiya var. langbianensis

Objective  To improve the weak dimensional stability of solid wood products in the environment where oil and water coexist, and further explore the potential application of solid wood in the various fields of public catering service furniture, food and seasoning packaging, kitchen and bathroom furniture as well as wooden products in living- and dining-room.

Method  Methyltrimethoxysilane (MTMS) and hydrochloric acid were mixed according to the volume ratio of 4︰1. After ultrasonic hydrolysis in an ice bath, Pinus kesiya var. langbianensis wood was modified by impregnation. The effects of different MTMS pre-hydrolysis reaction time (0, 30, 60, 120, 180 and 240 min) on hydrophobic and oleophobic characteristics of wood surface were studied. The changes in wood structure and properties before and after modification were comprehensively characterized by scanning electron microscope, contact angle analyzer, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and thermal gravimetric analyzer.

Result  The surface of wood was bonded with low surface energy groups of Si—CH₃, Si—O—Si, Si—OH etc. after modification, and their surface properties were changed from complete infiltration by water and oil to the dual-hydrophobic and oleophobic performance. Furthermore, the water contact angle change of modified wood surface was significantly greater than that of oil contact angle. The water contact angle increased from 73.60° to 88.31° with the increase of the pre-hydrolysis time from 0 to 240 min, while the oil contact angle only had a slight fluctuation around 50.50°. The thermal stability of the MTMS - modified wood was also promoted, the mass residual rate increased, and the maximum thermal degradation temperature was raised by 6 ℃. The final water and oil absorption rate were significantly reduced by 58.83% and 83.90%, respectively. There was an optimum surface dual-hydrophobic and oleophobic performance with the effective impregnation when the pre-hydrolysis time was 30–60 min.

Conclusion  The facile modification of MTMS provides the theoretical foundation and technical support for the development and utilization of novel hydrophobic and oil-repellent functional wood.