Processing and Characterization of Natural Fibre Reinforced Composites Using Lignin Phenolic Binder

Natural fibre-reinforced composites were prepared using a lignin-phenolic resol binder, in which 30 wt.-% of the phenol was substituted by a modified lignosulfonate from renewable resources. The reinforcement of the lignin phenolic binder matrix was accomplished by different natural fibres. The non-woven flax, flax/wood and flax/kenaf fibre mats were impregnated with the lignin-phenolic binder and they were compression-moulded at elevated temperature. The curing condensations of the synthesized lignin phenolic resins were characterized by differential scanning calorimetry. Water absorption, thickness swelling and flexural strengths of the natural fibre-reinforced composites were determined, as well as their thermal stability using thermogravimetric analysis. The flexural strengths of the flax/wood and flax/kenaf composites were higher than those of the flax reinforced composite. Morphological analysis using scanning electron microscopy showed an enhancement in fibre/matrix interaction for the flax/wood and flax/kenaf fibre mixtures.