THERMAL COMPRESSION EFFECT ON SEVERAL PROPERTIES OF 8-YEAR-OLD WARU GUNUNG (HIBISCUS MACROPHYLLLUS) WOOD

Abstract

The study aimed to investigate the effect of thermal compression on the properties of 8-year-old waru gunung wood. Wood specimens with the dimension of 25 mm100 mm150 mm in thickness, width and length, respectively were heated at 180 ˚C and 200 ˚C for 4 h. During the heating process, the specimens were subsequently compressed at 2.452 N mm⁻² for 40 mins at each temperature. Changes in the wood chemical structure were examined using the pyrolysis-gas chromatography-mass spectrometry, the wood physical properties were tested according to ASTM D143-94, the wood surface hardness was tested using a Universal Testing Machine and the wood discoloration was examined using the CIELab method. The changes in crystallinity degree was examined using x-ray diffraction and cell structure were collected as supporting data. Results showed that the thermal compression at 180 ˚C and 200 ˚C caused severe degradation on the specimen carbohydrate but less for lignin. The sum effect of thermal compression on the specimens also consecutively increased the density by 34.24% and 41.87% and surface hardness by 52.78% and 63.09% and decreased the swelling thickness by 38.54% and 47.03% and the equilibrium moisture content by 36.53% and 38.59% at 180 ˚C and 200 ˚C, respectively. Thermally compressed specimens also had darker colours, glossier surfaces and smoother texture compared to non-thermally compressed specimens.