Effect of light-delignification on mechanical, hydrophobic, and thermal properties of high-strength molded fiber materials

This study developed a high-strength molded fiber material (HMFM) using pulp fibers, which could be a good substitute for plastic and solid wood materials. The surface composition, microstructure and thermal properties of HMFM were investigated by XPS, SEM and DSC, respectively. The SEM observations showed that the obvious adhesive substances and agglomeration appeared among fibers, and the inter-fiber contact area and binding tightness increased after the light-delignification. The XPS examination showed that the oxygen-rich composition on the outer surface of HMFM were reduced, and the outer surface coverage of lignin increased from 70.05% to 90.15% after the light-delignification. The DSC observation showed that the thermal stability of HMFM decreased, the temperature for the maximum rate of mass loss decreased from 370 °C to 345.6 °C, and the enthalpy value required for decomposition was reduced from 110.8 J/g to 68.0 J/g after the light-delignification. The mechanical and hydrophobic properties of HMFM were obviously improved after the light-delignification. When the content of lignin decreased from 24.9% to 11.45%, the density of HMFM increased by 6.0%, the tensile strength increased by 22.0%, the bending strength increased by 23.9%, and the water contact angle increased from 64.3°–72.7° to 80.8°–84.3°.