From Natural Woods to High Density Materials: An Ecofriendly Approach

Recently, different methods have been proposed to develop wood materials, termed "densified woods", with density increment and improvement in mechanical proprieties. Almost all the proposed methods involve the use of reducing agents and strong bases. In this work, a new method has been developed involving the use of less polluting agents. The formation of densified woods is divided into two steps: delignification involves the removal of lignin, hemicelluloses, and shorter chains of cellulose, whereas densification involves the plastering of the delignified woods. The obtained materials showed a density increase of two to four times. The obtained densified woods were characterized by spectroscopic, microscopic, and thermogravimetric techniques and mechanical tests. The characterizations aimed at determining the variations of chemical and structural compositions of the samples after delignification and densification processes, showing, respectively, a decrease in lignin and a significant increase in the density and force necessary to bring the materials to yield. The final density of wood was two to three times higher and the force necessary to reach the yield point reached more than three times the initial one for some of the studied samples. These characterizations showed how different woods, with different properties, reach comparable densities and final mechanical properties after delignification and densification process. The increased mechanical properties of the materials allow their application in place of other composite woody materials.