Abstract
Abstract Alkaline lignin and de-alkaline lignin were liquefied in phenol with H2SO4 or HCl as catalysts. Liquefied lignins were reacted with formalin under weakly alkaline condition, and in this manner, alcohol-soluble resol-type phenol-formaldehyde (PF) resins (PFlignin) were prepared. Small particles of albizia [Albizia falcataria (L.) Fosberg] passing 100-mesh sieve were impregnated with these resins, and the resulting molded test plates (MTPlignin) with the dimensions of 10×10×0.4 cm3 were analyzed. Differential scanning calorimeter revealed that the PFlignin resins need higher temperatures for curing than those of industrial PF resin (control). MTPlignin has higher internal bonding and bending strengths than those of the MTPcontrol. Thermogravimetric analysis of MTPs shows three distinct degradation rates, and the following heat resistance was found: MTPcontrol>MTPAL>MTPDAL. MTPs have, after carbonization at 800°C, a uniform internal structure as revealed by dimension shrinkage analysis.
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