Improvement of the mechanical properties of sawdust wood fibre—polystyrene composites by chemical treatment

The mechanical properties of compression-moulded polystyrenes filled with sawdust wood residue of softwood and hardwood species have been investigated. The tensile modulus at 0.1% strain and the tensile strength, elongation and energy at the yield point are reported. The suitability of sawdust wood residue as a filler for thermoplastics has been tested using two different mesh sizes (20 and 60), as well as by varying the weight percentage of fibres from 10% to 40%. Moreover, to improve the compatibility of the wood fibres with the polymer matrices, different treatments (e.g. graft copolymerization) and coupling agents (e.g. silanes and isocyanates at various concentrations) have also been used. The extent of the improvement in mechanical properties depends on the fibre loading, on the particle size of the fibre, on the concentration and chemical structure of the coupling agents, and on whether special treatments (e.g. coating or grafting of the fibre) are used. The mechanical properties of the composites are improved up to 30% in the case of fibres having a mesh size 60 and when up to 3% of isocyanates was used.