COEFFICIENT OF THERMAL EXPANSION OF RUBBERWOOD (<em>HEVEA</em> <em>BRASILIENSIS</em>) IN CONVECTIVE DRYING PROCESS

Abstract

Rubberwood drying is an energy-intensive process where drying defects are the main problems faced by the wood industry. The main objective of this study is to evaluate the coefficient of thermal expansion (CTE) of rubberwood to have a better understanding of the effect of temperature over the distortions of rubberwood during drying. Rubberwood samples were first dried at three different hot air temperatures and the mechanical properties of dried rubberwood samples were tested in the preliminary experiment to determine the suitable temperature condition for further evaluation of the CTEs of rubberwood samples. The CTEs of rubberwood in tangential and radial directions were evaluated through strain gages at three different moisture content (MC) levels: above 60%, at 12% and almost 0% (dry state). Based on the findings of this work, the CTEs of rubberwood in the tangential direction were found to have higher values than that of radial direction. The rubberwood samples had the highest CTEs values at 12% MC in both directions. Also, no significant differences were found between the experimental and expected CTE values of rubberwood as a function of specific gravity in the dry state.