Preparation and Characterization of Novolak Phenol Formaldehyde Resin from Liquefied Brown-Rotted Wood
The brown-rotted wood was liquefied in phenol with phosphoric acid as catalyst and the resulting liquefied products were condensed with formaldehyde to yield novolak liquefied wood-based phenol formaldehyde resin (LWPF). The results showed that brown-rotted wood could be more easily liquefied than sound wood in phenol. The residue content of liquefied wood decreased continually with the progress of brown-rot decay. Both water wash and neutralization and water wash slightly improved the thermofluidity and curing properties of LWPF with a small reduction of LWPF yield. An increase in phenol to wood (P/W) ratio from 2 to 3 slightly improved the flow property of LWPF, but with an accompanied by 20% deduction in the product yield. Increased liquefaction time from 30 min to 60 min showed no significant influence on the resulting LWPF. The moldings fabricated from LWPF yielded higher charpy impact, flexural and flexural modulus strength but yielded lower temperature deflection under load than that of the commercial novolak resin.