Optimization of oil heat treatment process to enhance rubberwood properties using response surface methodology

Rubberwood is an eco-friendly wood. Natural rubber is considered as the excellent agricultural product and it was utilized in many industries. The natural durability is very low in rubberwood. In dry as well as in green condition, it can be affected by wood borers and fungus. The objectives of this study are to determine the effect of resistance to white rot fungus, to assess the significant changes on the physical properties, chemical properties and mechanical properties of rubberwood after the heat treatment (172 - 228°C) in palm oil and to optimize the heating variables to enhance the properties of rubberwood treated with oil using response surface methodology. The colour of oil heattreated rubberwood becomes uniformly darker. Hydrophobicity, dimensional stability and fungal resistance were improved by the heat treatment with respect to increase in treatment temperature. However, the mechanical properties of treated rubberwood were reduced compared to the untreated wood. The treatment resulted in changes to the wood chemical constituents, mainly the degradation of hemicelluloses which is believed to be principal reason for alterations in wood properties. The oil heat treatment reduced the chemical constituents by 11.7 % in total in the rubberwood. The depolymerization of hemicellulose results in reduction on bending strength of wood. The maximum reduction in Modulus of Rupture, Modulus of Elasticity, Compression and Shear were approximately 47%, 8%, 21% and 33% respectively compared to the control specimen. This study shows that there is some reduction in density and equilibrium moisture content and positive high in moisture excluding efficiency values. The density of rubberwood was decreased gradually from 629 kgm-3 (untreated) to about 591 kgm-3 (at 228°C/180min). The Equilibrium Moisture Content also decreased from 12.42 % to 7.97 % (at 228°C/180min). The density reduction was probably due to the hemicelluloses and cellulose degradation. The higher moisture excluding efficiency value indicated that the wood is stable and excludes water after oil heat treatment process. The treated wood has moisture excluding efficiency value in the range between 28-50% depending upon the treatment temperature and time. The fungal resistance effect on the treated rubberwood was examined by exposing the wood to white rot fungi (Pycnoporus sanguineus) for 12 weeks and the weight loss was determined. The samples were tested at 13 different treatment conditions. Among those conditions, the lowest weight loss (8.23 %) was observed at 228°C and 180 min, with the decay by Pycnoporus sanguineus for rubberwood species. This research helps in improving various properties of rubberwood and biological durability by oil heat treatment process. Thus with the outcome of this research, the optimized heat treatment conditions could be suggested by the response surface methodology models to enhance the quality of rubberwood.

Preview PDF FH 2015 4RR.pdf Download (1MB) | Preview

Actions (login required)

View Item