Hydrothermally treated wood as reinforcing filler for natural rubber bio-composites

Hydrothermal treatment was considered as a method for modification of oriental beech wood to be used as reinforcing filler for natural rubber. Surface energy of treated wood fibers and their interaction with natural rubber were studied by water contact angle of wood and dynamic-mechanical-thermal analysis of formed bio-composites and compared with those for untreated and silane-treated wood fibers. Hydrothermal treatment of wood was performed at two temperatures of 140 degrees C and 160 degrees C, and bio-composites were prepared by melt mixing method. Results showed that water contact angle of untreated wood increases by hydrothermal treatment and silane modification of wood fibers, which the latter has the highest value. Dynamic-mechanical-thermal analysis of bio-composites showed that hydrothermal treatment reduced interactions between wood fibers and increased interaction between fibers and rubber which resulted in better dispersion of fibers, observed by scanning electron microscopy. In order to investigate reinforcing effect of hydrothermally treated wood fibers, mechanical properties of bio-composites in tension was studied, and improvement in tensile strength and elongation at break for bio-composites containing treated fibers was observed, which was correlated to the stronger wood fiber-rubber interface compared to untreated ones. Wood fibers treated at 140 degrees C showed better mechanical properties, which was comparable with silane modified fibers.