Abstract:

Objective: The aim of current study is to improve the hydrophobicity and water repellency of wood by constructing double layer hydrophobic system in wood internal and external surfaces comprising a continuous linseed oil film with rough wax structure. Method: Linseed oil, mixed wax and oil/wax hybrid emulsions were prepared and their properties were tested. The two- and one-step impregnation process was used to modify cathay poplar (Populus cathayana), followed by the heat treatment at 70 ℃ (two-step process) or 90-103 ℃ (one-step process) to form double layer hydrophobic barrier. The internal morphology of samples was characterized by field emission scanning electron microscopy (FE-SEM), and the weight percent gain, surface hydrophobicity, water absorption and volume swelling rate of treated samples were measured. Result: 1) The average particle size of linseed oil emulsion was about 195.6 nm, and its change rate under 60 days room-temperature storage was only 2.45%. The wax/oil hybrid emulsions also presented great stabilities after centrifugation test. 2) FE-SEM images showed that both two- and one-step treatment processes could produce oil-wax double layer hydrophobic system with water repellent film and rough structures. 3) The initial contact angle of treated wood on cross sections was nearly 150° and kept a good stability within 80 s detection, the one-step process treated wood presented a better performance than that of the two-step on the tangential section. 4) The hybrid emulsions could further improve water repellency, and the water repellency efficiency(WRE) was above 35% and 45% with two- and one-step treatment, respectively. Clearly, one-step method performed better properties and simpler process. Conclusion: Linseed oil/mixed waxes hybrid emulsions could improve the hydrophobicity and water repellency of poplar at the same time, it may be an eco-friendly, energy-saving and low cost method for wood hydrophobic modification.

Key words: wood, wax, linseed oil, emulsion, hydrophobicity