The effect of sodium hydroxide pre-treatment on the densification properties of low-density paraserianthes falcataria plantation timbers
Wood densification was done by compressing the wood using hot-press machine, with temperature and pressure. By densification, low-density wood can reach higher density after the cell walls were collapsed under condition. Densification can be done by chemical treatment and compression to achieve the...
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| Format: | Thesis |
| Language: | English English |
| Published: |
2022
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| Online Access: | https://eprints.ums.edu.my/id/eprint/40514/1/24%20PAGES.pdf https://eprints.ums.edu.my/id/eprint/40514/2/FULLTEXT.pdf |
| Summary: | Wood densification was done by compressing the wood using hot-press machine, with temperature and pressure. By densification, low-density wood can reach higher density after the cell walls were collapsed under condition. Densification can be done by chemical treatment and compression to achieve the maximum density by fully compacting the microstructures. Low-density timber species can be used as an alternative to hardwood species. The higher mechanical properties of densified wood products allow their use in diverse and advanced applications. This study was designed to evaluate the morphological, physical, mechanical, and dimension stability properties of untreated (D0) and treated (D3, D6, D9) densified Paraserianthes falcataria glulam. Besides that, this study was aimed to investigate the effects of different alkaline concentrations and the relationship between cell lumen areas with morphological, physical, mechanical, and dimension stability properties of untreated (D0) and treated (D3, D6, D9) densified P. falcataria glulam. Three different concentrations of NaOH (3%, D3; 6%, D6; 9%, D9) were used for alkaline pre-treatment with 0% NaOH as control and prepared according to soda pulping method. The untreated and treated laminas were compressed at 105°C temperature and 6 MPa pressure for 30 minutes with 8 mm metal stopper, followed by cooling phase for 10 minutes without releasing the plate. After conditioning, laminas were planned and laminated into 3 layers using Polyvinyl acetate (PVAc) as adhesive, before trimmed into desirable sizes. ASTM, JAS, BS and TAPPI were used generally for lignin content determination, static bending, compressive strength, hardness, compressive strength, contact angles, delamination, block shear, moisture content, thickness swelling and water absorption, while Scanning Electron Microscopy and Chromaticity Reader 10 were used to determine cell lumen areas and chromaticity values. Some results obtained shows improvement after alkaline pre-treatment and densification, such as in total differences of chromaticity values (35.7%), Modulus of Elasticity and Modulus of Rupture of edgewise (31% and 20%), Modulus of Elasticity of flatwise (4.5%), compression perpendicular to the grain (10%), hardness of tangential and radial (21.3% and 18.1%), delamination (7.2%), thickness swelling and water absorption (2.1% and 3%), moisture content for lamina and glulam (1.3% and 8.8%), respectively, density profile for lamina and glulam (24.6% and 9.1%), contact angles using water and PVAc (43.3% and 5.3%), compared to the control. While, other tests show declining results after alkaline pre-treatment and densification, such as reduction of lignin content (55%), Modulus of Rupture of flatwise (25.4%), compression parallel to the grain (22.2%), hardness of longitudinal (13.4%), block shear (10.6%) and density (27.6). In general, the range of Pearson’s coefficient correlations for these studies were in the level of correlation of moderate positive linear and moderate negative linear. In conclusion, this study can be sum up that some properties showed up to 35% improvements after being treated and densified, while a few shows decline and no improvement. This result would be influenced by the natural characteristics of P. falcataria, NaOH or densification. As there were many studies had been done to overcome the disadvantageous characters in woods as to improve its quality, value adding and maximize the utilization of the materials, probably more research should have been done for low-density plantation timber. |
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