Fast-growing willow (Salix viminalis) as a filler in polyethylene composites

The study investigated the possibility of using wood flour obtained from fast-growing willow chips (Salix viminalis) as an alternative for standard hard- and softwood flours used in the production of wood polymer composites (WPCs). The composites contained willow flour and polyethylene matrix (OPCs) were prepared, characterized and compared with other WPCs which had been filled with hard- or softwood flours. Moreover, the structural and functional properties were investigated and discussed. Greater hemicellulose contents and lower lignin contents in OPCs resulted in better impact strength values of those materials. Which is interesting, the chemical composition of OPCs was found similar to that of hardwood-filled WPCs, but at the same time no deterioration was noted in the strength properties of OPCs, which was observed and which is typical for that kind of WPCs. That can be explained by a slightly higher share of cellulose in OPCs (in comparison with hardwood-filled WPCs) and also by a greater number of hydroxyl groups which may have some positive contribution to the structural strength of the composites. The results showed that the OPCs had slightly better mechanical properties against various WPCs. Hence, the willow flour can be used in the production of WPCs as a cheaper alternative for the hardwood filling materials.