Improving Hydrophobicity of Tropical Hardwood along Axial Positions

O.A Adegoke,O.O Ajala,E.A Adelusi,A.J Oloketuyi,F.G Adebawo

doi:10.4314/jasem.v25i8.8

Abstract

Wood is hygroscopic and is considered dimensionally unstable materials when exposed to wet conditions. To increase the hydrophobicity of wood, this study focused on the modification of tropical hardwood (Triplochiton scleroxylon) along different positions of the stem using acetic anhydride The weight percent gain (WPG) was determined and acetylation reaction was confirmed with FTIR. The dimensional stability of the wood was characterized by water absorption (WA), volumetric swelling (VS), anti-swelling efficiency (ASE), and water repellent efficiency (WRE). Data obtained were subjected to analysis of variance at α0.05. It was observed that the weight gain (WG) by acetylation increases along the axial position (base to top) of T. scleroxylon wood. IR-spectra confirmed properly the substitution of the acetyl group. The treatment resulted in a marked improvement in the WA and VS, ASE, and WRE of acetylated T. scleroxylon wood were also found to improve considerably from base to top of the wood. It could be said that the WPG and hydrophobicity increased, but the percentage of water absorption and volumetric swelling diminished. Hence, the modified wood showed good hydrophobicity and improved dimensional stability.

Highlights

Wood is hygroscopic and is considered dimensionally unstable materials when exposed to wet conditions
Wood has been used by mankind based on its inherent properties, like any specific part of a tree of particular specie that could be found in the neighborhood was utilized to achieve the best performance when it was used in construction, for different types of tools, or purposes not included in the practical tasks of life
The weight percent gain (WPG) along the axial positions ranged between 18.16 – 17.58 % while the highest and lowest recorded at the top and base of the wood respectively an increase in weight gains along the axial direction of sampled wood

Summary

MATERIALS AND METHODS

Wood Preparation: T. scleroxylonwood was converted into 20×20×60mm (radial×tangential×longitudinal) wood blocks withno defects. Wood samples (MC ~7%) were introduced into stainless steel pressure reactor vessels containing the acetylation liquid, (i.e., acetic anhydrideand acetic acid (92:8)). To achieve pre-impregnationof the wood with the reagent, the temperaturewas set at 25°C and 10 -15 bar for 30 minutes the reaction temperature was set at 120 °C for 0, 60-, 120-, 180-, 240- and 300 minutes with 20 wood blocks per period of exposure. The wood samples were air-dried andthen oven-dried at 105±2 °C for 24 h, the weight was recordedas W2. ASE= anti-swell efficiency, Su= volumetric swelling coefficient of unmodified wood samples, Sm= volumetric swelling coefficient of modified wood samples. FT-IR Analysis:The acetylated and unmodified samples were ground in a Wiley Mill machine and sieved to 40-mesh particle size. Extractives-free wood samples were prepared using acetone and hot water following a standard method (TAPPI T264 CM97, Oct.2007) for FT-IR spectrophotometry. The IR spectra of the acetylated and unmodified samples were. Acetylated and unmodified means were separated using theDuncan multiple range test at α0.05

RESULTS AND DISCUSSIONS

Water Repellent Efficiency

Conclusion