Utilization of Sawdust and Wood Ash as a Filler in Natural Rubber Composites

This study focuses on the feasibility of using sawdust (SD) and wood ash (WA) as a filler in natural rubber composite. Both SD and WA were characterized by several techniques prior to being incorporated into natural rubber (NR). Properties of the rubber composites filled with various loadings of SD and WA, including cure characteristics, mechanical properties and morphology, were measured. Results reveal that the particles of SD and WA are relatively large and irregular. The main compositions of SD are cellulose, lignin and hemicellulose whereas those of WA are SiO2, Al2O3, Fe2O3, carbonates and oxides of the alkali metals, namely CaO, MgO, Na2O, K2O, etc. After being incorporated into NR, hardness and modulus of the NR composites gradually increase with increasing SD and WA loadings. Compared with SD, WA provides a slightly lower magnitude of reinforcement, possibly due to its lower rubber-filler interaction. However, the addition of WA significantly shortens the vulcanization time due to its high basicity. Interestingly, tensile strength of the NR composites is not significantly impaired with the addition of SD or WA up to 30 phr. Nevertheless, due to their relatively large particle size, both SD and WA show considerably lower magnitude of reinforcement than carbon black (CB). The results indicate the potential use of SD and WA as an inert filler for cost-reduction purpose in the rubber industry which helps to raise the environmental credentials of the product.

Automated summary

This study examined the feasibility of using sawdust and wood ash as fillers in natural rubber composite. The results indicated that adding sawdust and wood ash gradually increased the hardness and modulus of the rubber composites, while wood ash provided a slightly lower magnitude of reinforcement and significantly shortened vulcanization time.