Development of wood-substituted composites from highly filled polybenzoxazine-phenolic novolac alloys

Highly filled wood-substituted composites from matrices based on polymer alloys of benzoxazine resin (BA-a) and phenolic novolac resin using Hevea brasiliensis woodflour as a filler were developed. The results reveal that phenolic novolac resin can significantly reduce the curing temperature of the neat benzoxazine resin, thereby minimizing the degradation of woodflour filler during processing. The limiting oxygen indices (LOIs) of all the BP alloys were above the self-extinguishable limit i.e. >26. In addition, the LOI values were found to moderately increase whereas the rate of burning decreased as the novolac fraction in the resin mixtures increased. Furthermore, a solvent resistance experiment and thermogravimetric analysis revealed that the suitable phenolic novolac content should not exceed 20 wt%, to avoid the presence of unreacted phenolic in the alloy networks. The outstanding mechanical performance of the resulting wood composites is attributed to the strong interfacial interaction between the BP alloys and the woodflour filler.