Formaldehyde-free environmentally friendly lignocellulosic composites made from poplar and lignin obtained from paper mills

Traditional wood-based panels composed of wood and petroleum based adhesives is widely used in furniture manufacturing and construction industries. However, these adhesives are not biodegradable, inhibiting the recycling of artificial board. More seriously, the emission of carcinogenic formaldehyde will lead to severe pollution and environmental issues. This study presents a method for preparing self-bonding composites. Waste poplar powder is used as raw material in the biocomposite, in which exogenous lignin is added, and lignin is extracted from the waste of the paper industry - black liquor, which is beneficial to the environment and the recycling of resources. The resulting biocomposites are characterized by aldehyde-free, better strength, and water stability. The dimensional stability and mechanical strength, bending strength (84.40 MPa), and tensile strength (35.40 MPa) of the biocomposite are 2.0 and 1.6 times that of composites obtained by hot pressing without pretreatment and are 2.7 and 2.4 times that of medium density fiberboard (MDF), lignin plays an important role as an adhesive, which is the key to improving mechanical properties. Moreover, the biocomposite features higher water stability and fire resistance than the traditional wood fiberboard. In conclusion, the developed black liquor-wood biocomposites are potential alternatives used to replace the formaldehyde wood-based fiberboard.