Production of fully natural-based boards from hemp fibers and rice husk particles. Investigation on morphology, mechanical properties, thermal, hydrothermal and photo-thermal ageing

In the present study, two different crop by-products (namely, hemp long fibers and rice husk particles) have been used to produce natural-based boards (fiber- and particleboards) by using corn starch as binder in order to have the consistence and strength required for internal panels and furniture. A simple and economic transformation process based on the use of hot compression molding has been employed. Mixing fibers or particles with binder has been carried out by simple impregnation in a water solution. Long fibers as well as small particles might be processed with the same machine avoiding any health and pollution problems. Fully green boards have been obtained and characterized in terms of morphology, moisture absorbance and mechanical properties (assessed by both dynamic-mechanical thermal analysis and tensile tests). In addition, the influence of different relative humidity levels on composite modulus has been investigated. Long fibers have proven to be capable of sustaining approximately double loading with respect to articles. Furthermore, the prepared boards have been subjected to three different accelerated aging conditions: namely, i) high temperature (thermal ageing); ii) high temperature combined with humidity and iii) high temperature in the presence of UV radiations (photo-thermal ageing). After these tests both boards have maintained good mechanical properties, with a restrained reduction of their storage modulus (lower than 20% with respect to the prepared materials).