Depolymerization of Lignin Extracted from Low-Range Carbon by the UV/Tio2 Radiation Method and its Use in the Elaboration of Synthetic Wood Boards

On this research, lignin depolymerization by ultraviolet radiation and catalyzed by titanium dioxide was studied and later it was used as a copolymer in making boards with rice husks. Lignin was extracted from a low-rank coal sample coming from Paipa-Boyacá using Sosa Method. Depolymerizations on samples of 100 ml 50 mg/L lignin for 0, 2, 6, 10 hours and catalyst amounts in ratios 1:1; 1: 3.3; 1: 6.6; 1:10 lignin and TiO2 respectively were standardized by irradiation with 45W UV light. Results allowed selecting optimal values of 6 hours of irradiation and the catalyst in the proportion of 1 lignin by 3.3 of TiO2 for depolymerization. It produced 22% degradation on lignin. Later, depolymerized lignin was activated by the hydroxymethylation reaction with formaldehyde. For boards, preparation components were mixed in proportions of 60% rice husk, 7.4% lignin, 14.9% melamine and 17.7% formaldehyde. The mixture was heated to 100 ° C for one hour in molds. Three boards were produced with the above-mentioned proportions and with following characteristics: board 1 was made with unmilled rice husk and Kraft lignin (Sigma-Aldrich); board 2 was made with milled rice husk and Kraft lignin and board 3 was made with milled rice husk and activated lignin. All boards were subjected to mechanical tests of bending, compression, and traction and water absorption. Board 2 showed the most suitable results according to ASTM D 143 norms.