Lignocellulose/pitch based composites

Carbon composites were prepared by blending sawdust and petroleum pitch in a proportion of 50:50 wt% and then moulding and carbonising them up to 900 °C. The sawdust reacted with the pitch during the processing of the composite, giving rise to an isotropic and highly distorted material. Treatment of the sawdust with sulphuric acid caused important changes in the composition of the filler, the resultant composites exhibiting a microstructure in which the honeycomb lignocellulosic structure was preserved, whereas the pitch progressed to form an anisotropic matrix. On the other hand, treatment of the pitch with magnesium oxide contributed to the development of an anisotropic matrix also with sawdust, reduced porosity and prevented deformations of the composite. The combination of the treated sawdust and treated pitch resulted in composites that had adopted the positive characteristics of the precursors, i.e. the thermal and structural stability of the filler and the ability of the binder to generate materials of low porosity and high flexural strength. The formulation of composites with different filler/binder ratios (40:60, 50:50 and 60:40 wt%) showed that flexural strength can be improved by increasing the binder content.