Preparation of a Lignin-based Composite and Its Properties

Enzymatic hydrolysis (EH) lignin was modified with formaldehyde. TGDSC and PY-GC-MS analysis methods were adopted to characterize the differences between EH lignin and the modified lignin. The modified lignin was then mixed with wood sawdust and made into a lignin-based composite under the following conditions: pressure of 2 to 5 MPa, temperature of 175 to 190 C, and the modified lignin dosage of 20% to 70%. The effects of pressure, temperature, and the modified lignin dosage on the properties of the composites were also evaluated. The pressure of 2 MPa was not enough to make a strong composite, and the composite with low dosage of modified lignin could not resist water, which signifies pressure and the ratio of modified lignin to sawdust are vital factors. Temperatures of 175 C and 190 C did not make much difference to change the mechanical properties of the composites. The composites which were made under 3 MPa, 180 C, and the ratio of 1:1 modified lignin to wood sawdust was of fair quality. The samples made with the modified lignin dosage of 70% under 2MPa at 180 C for 10min showed a low thickness swelling and low rates of water absorption from humid air and liquid water. Their free formaldehyde contents were also low and met Grade 2 in the national standard of China.