THERMAL DEGRADATION PROFILE OF CHEMICALLY MODIFIED WOOD SAWDUST
Gmelina arborea sawdust was chemically modified using 4% and 8% concentrations of NaOH solution for 30 and 90 minutes soaking times. The influence of this modification on the chemical composition and thermal properties of samples were investigated. Chemical characterization of samples revealed that the percentage content of hemicellulose decreased from 24.5% in the unmodified sample to 20.8%, 17.6% and 15.2% in samples soaked in 4% NaOH solution for 90 minutes, 8% NaOH for 30 and 90 minutes respectively. The amount of lignin decreased from 25.0% in unmodified samples to 19.0% when the sample was treated with 8% NaOH for 90 minutes. A moisture content of 9.0% and 2.5% were recorded in unmodified and sample treated with 8% NaOH for 90 minutes respectively. However, the cellulose content increased from 38.1% in unmodified sample to 60.1% when the sample was treated with 8% NaOH for 90 minutes. The percentage weight loss increased as concentration and modification time increased. Functional groups analysis by Fourier Transform Infrared Spectroscopy (FTIR) showed evidence of reduction in OH and removal of C=O groups associated with the wood polymers after chemical modification. Thermogravimetric analysis revealed that samples treated with 4% NaOH for 90 minutes presented the highest onset and peak degradation temperatures of 274.0°C and 372.1°C respectively. From these results, it can be concluded that modification with 4% NaOH solution for 90 minutes imparted a significant improvement on the thermal stability of Gmelina arborea sawdust.
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