CHARACTERISATION OF SELECTED WOOD PROPERTIES OF THERMALMODIFIED Bambusa vulgaris SCHRAD.EX J.C.WENDL

ABSTRACT

The preservative treatment of non-durable lignocellulosic materials, such as Bambusa vulgaris (bamboo) enhances its service life. Thermally modified lignocellulosic biomaterial is better than chemically treated products because it is environmentally friendly. However, there is a dearth of information on the characterisation properties of thermally modified Bambusa vulgaris. This study was therefore conducted to characterise the properties of thermally modified Bambusa vulgaris. One thousand and eighty (30 cm x 2 cm x 0.5 cm) bamboo strips were thermally modified in a heat-chamber at 100, 110, 120, 130 and 140 °C each, for 10, 20 and 30 minutes, under constant pressure (220 N/m2 ) in factorial arrangement in completely randomised design with 5 replicates. Untreated strips served as control. The strips were laminated into boards using cold press for 24 hours and Fibre Diameter (FD), Fibre Cell Wall (FCW), Fibre Lumen Width (FLW), Fibre length (FL) were measured. The Specific Gravity (SG), Equilibrium Moisture Content (EMC), Radial Shrinkage (RS), Water Absorption (WA), Compressive Strength (CS┴), Modulus of Elasticity (MOE), Modulus of Rupture (MOR), Shear Strength (SS) and Impact Bending (IB), chemical characteristics (cellulose, hemicellulose, lignin and ash contents) were determined using standard procedures. Samples were thereafter inoculated with Sclerotium rolfsii (Brown rot) and Pleurotus florida (White rot) using accelerated durability test procedure for 12 weeks and assessed for Weight Loss (WL). Samples were also assessed in Timber Grave Yard (TGY) using Weight Loss (WL) procedure. Data were analysed using descriptive statistics, ANOVA and regression at α0.05. The FD ranged from 11.51±2.07 µm (140°C/30 minutes) to 17.62±3.65 µm (control), FCW ranged from 5.96±2.13 µm (140°C/30 minutes) to 12.03±3.66 µm (control), FLW ranged from 2.64±0.12 µm (140°C/30 minutes) to 2.80±0.22 µm (control), while FL ranged from 2.05±0.28 mm (140°C/30 minutes) to 2.52±0.39 mm (control). The SG (0.6±0.1 and 0.5±0.1), EMC (10.5±1.3 and 6.8±1.2), RS (3.7±1.1and 1.6±0.6) and WA (46.6±13.5% and 32.7±2.2) were obtained in control and 140°C/30 minutes thermal-modified samples, respectively. The RS and WA at 100, 110, 120 and 130°C/30 minutes were 0.9±0.3, 1.2±0.4, 0.6±0.1, 0.6±0.1 and 38.4±5.3, 31.1±4.7, 26.4±3.8, 29.9±4.5%, respectively. The CS┴, MOE, MOR, SS and IB varied from 7.41±0.24, 5461.83±594.86, 18.39±2.01, 1.07±0.26 N/mm2 and 1.68±0.03 KJ/m2 , respectively in 140°C/30 minutes to 36.14±0.11, 29,703.50±4192.77, 56.29±1.86, 3.88±0.50N/mm2 and 2.30±0.02 KJ/m2 , respectively for untreated samples. The cellulose (46.46±0.11% and 42.19±0.18%), hemicellulose (35.59±0.10% and 31.80±0.01%), lignin (29.11±0.12% and 26.17±0.13%), ash (0.92±0.02% and 0.63±0.01%) were obtained in control and 140°C/30 minutes thermal-modified samples, respectively. The highest WL was obtained from untreated samples inoculated with Sclerotium rolfsii (6.1±0.3%) and Pleurotus florida (5.1±0.9%), while the least WL of 1.8±0.2% and 1.1±0.2%, respectively was recorded for samples modified at 140°C/30 minutes. The WL of untreated samples in TGY was 28.2±14.1%, while the least WL (25.1±2.9%) was observed for 140°C/30 minutes thermal-modified samples. The IB and EMC accounted for 83.9 and 53.8% variation of chemical characteristics. Thermal modification at 140°C for 30 minutes improved dimensional stability and durability of Bambusa vulgaris. Increase in temperature and time of thermal modification reduced strength properties and chemical characteristics of Bambusa vulgaris.