Consolidation of Fir Wood by Poly(vinyl butyral-co-vinyl alcohol-co-vinyl acetate) Treatment: Study of Surface and Mechanical Characteristics

The ability of poly(vinyl butyral-co-vinyl alcohol-co-vinyl acetate) (PVBVA) to consolidate Fir wood was studied in terms of the surface and mechanical properties’ changes. Two variables were considered to treat the wood: (i) the concentration (5 and 10 wt.%) of PVBVA solutions and (ii) the method of application (brushing and immersion). The presence of PVBVA on the wood surfaces was confirmed by infrared spectroscopy. Surface roughness measured by optical profilometry did not reveal changes in the topography of the samples, and appropriate visual appearance was confirmed. Contact angle measurements showed that a droplet of the 10%-PVBVA solution needed ~50 s to reach the same contact angle decreasing rate as that measured for the 5%-PVBVA solution, suggesting there was some kind of induction time till the spreading process was no longer controlled by the viscosity, but by the solution-wood interactions. Water contact angle (WCA) measurements proved a more hydrophobic surface of the PVBVA-treated samples, compared to untreated wood. Mechanical characterization of the samples was done macroscopically by a three-point bending test and locally by the Shore D and Martens hardness (MH). Only results from MH experiments provided comparative results, indicating that treatment with PVBVA solutions increased wood hardness locally, being enhanced with solution concentration. The best surface mechanical properties were obtained for the samples immersed in the 10%-PVBVA solution.