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The heat treatment of wood is an environment-friendly method for wood preservation. The heat treatment process only uses steam and heat, and no chemicals or agents are applied to the material during the process. Tests have shown no harmful emissions are apparent when working with the material. This process improves wood's resistance to decay and its dimensional stability. In this study, the density, compression strength and hardness of heat treated hornbeam (Carpinus betulus L.) wood were investigated. Wood specimens that had been conditioned at 65% relative humidity and 20 ºC were subjected to heat treatment at 170, 190, and 210 ºC for 4, 8, and 12 hrs. After heat treatment, compression strength and hardness were determined according to TS 2595 and TS 2479. The results showed that the decreases of compression strength and hardness were related to the extent of density loss. Both compression strength and hardness decreased with the increasing temperatures and durations of the heat treatment. While the maximum density loss observed was 16.12% at 210 ºC and 12 hour, at these heat-treatment conditions, the compression strength approximately decreased 30% and hardness values in tangential, radial, and longitudinal directions approximately decreased by 55%, 54%, and 38%, respectively. Hence, it was concluded that there might be a relationship between changes of these wood properties.

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The aim of this study was to investigate the effects of cellulose nanofibrils and nanoclays on the mechanical, thermal, and morphological properties of polyhydroxybutyrate and polylactic acid bio-polymers. Polyhydroxybutyrate and polylactic acid as a polymer matrix and nanoclays and cellulose nanofibrils as reinforcing nano-fillers were used to prepare the biopolymer nanocomposites in twin screw extruder. Density, flexure strength and flexure modulus, tensile strength and tensile modulus, impact strength, thermal properties, and morphological characterization of the obtained biopolymer nanocomposites were determined. According to the obtained results, densities of the biopolymer nanocomposites were found to decrease with addition of the bio-fillers, and it was determined to be decreasing the density due to increasing the porosity in biopolymer nanocomposites. Although the increasing in the porosity of biopolymer nanocomposites was found in scanning electron microscope pictures, the mechanical properties of the biopolymer nanocomposites generally increased as compare with neat bio-polymers. Thermal analysis conducted with thermogravimetric-dynamic thermal analysis and differential scanning calorimeter showed that thermal stability of the biopolymer nanocomposites generally improved according to the neat bio-polymers.

TiO2 filled Polypropylene (PP) nanocomposites were prepared with a single screw extruder and then by injection molding of the blends. Water absorption, density, mechanical properties, morphological characterization, FTIR analysis, and the thermal stabilities of the nanocomposites were investigated. The results showed that water absorption decreased and density increased as the amount of nano-TiO2 added increased. The mechanical properties improved for all formulations with the addition of nano-TiO2, except for the tensile modulus of elasticity and the izod impact strength. Thermogravimetric analysis (TGA) indicated that the thermal stability of the nanocomposites improved as the amount of nano-TiO2 increased. The melting and decomposition peaks of DTA increased as nano-TiO2 was added. The differential scanning calorimetry (DSC) results showed that the melting temperature (Tm) increased with the addition of nano-TiO2. Scanning electron microscopy (SEM) images of the nanocomposites showed uniform dispersion for 0.5, 1, and 2 % TiO2, but some agglomerations were found on the surfaces and in the fractured sides of the nanocomposites with 4 % TiO2. The agglomerates were determined by SEM mapping. The changes in the chemical structure of the nanocomposites were determined with Fourier transform infrared (FTIR) spectroscopic analysis. The FTIR results showed that the chemical structures of the composites were similar and that there were no major differences between the composites.

In this study, the influence of thermal treatment on color changes of six different wood materials was investigated. Test specimens were subjected to three different temperatures (160, 180, and 200°C) and durations (3, 5, and 7 h). The data obtained were analyzed using variance analysis, and then the statistical analysis of Tukey's test was conducted. After this treatment, the results showed that the color values of the six wood materials changed significantly. It was determined that L* (lightness) values decreased; the minimum change in L* was ∼4% for Juniper wood, and the maximum change in L* was ∼64% for Beech wood. The values of a* (red coordinate) and b* (yellow coordinate) showed varying levels of increase when the heat treatment conditions were 160°C for 3 to 7 h (not including Cherry wood), but the values began to decrease slowly after treatment at 160°C for 5 h. The ratios of the minimum and maximum color change in a* and b* were determined at 180°C for 3 h in Plane wood, 200°C for 5 h in Hazelnut wood, and 160°C for 3 h and 200°C for 7 h in Beech wood. As temperature and duration were increased, the minimum total color change (ΔE ab*) was ∼3.5% for 160°C at 3 h in Cypress wood, and the maximum total color change (ΔE ab*) was ∼50% for 200°C at 7 h in Cypress wood. © 2010 Wiley Periodicals, Inc. Col Res Appl, 2010

Thermal treatment of wood alters its structure due to degradation of wood polymers (cellulose, hemicellulose, and lignin), so the physical properties of wood are either improved or worsen. In this study, the effect of thermal treatment on density, equilibrium moisture content (EMC), and color of hornbeam wood was investigated. The color and density (air-dry and oven-dry density) were determined for the control and heat-treated samples, as well as their equilibrium moisture content at relative humidities of 35, 50, 65, 80, and 95%. The data showed that thermal treatment resulted mainly in darkening of the wood and the reduction of its density and EMC. It was found that the treatment temperature had a much more significant impact on color changes than the duration of the treatment. Generally, heat-treated wood color becomes darker than nontreated wood, so it can be used as decorative material. Because the EMC is lower, the heat-treated wood can be used in saunas and pool sides. Also, heat-treated wood can be used in outdoor applications because of lower density.