Effect of akali, esterification and silane surface treatments on properties of flax fibres

In the recent decades, flax fibres can be used as laminate reinforcements with polymer matrix materials to form natural composites, providing outstanding environmental benefits and other characteristics such as reduced cost and light weight. The composite properties are limited by the poor natural fibre/polymer matrix adhesion, which could be improved by chemical modifications. The fibre properties, such as thermal and mechanical properties, after the treatments have a direct effect on the composite behaviors. In order to investigate the effect of treatments on fibre properties, non-woven flax fibre mats were subjected to alkali, esterification and silane treatment. Fourier transformation infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and tensile tests were conducted on the virgin and treated flax fibres. It was found that all the treatments resulted in the removal of pectin and lignin component within the primary cell wall as evidenced by the characteristic IR peak change. The results showed that the thermal stability of non-cellulose part of flax fibres was highly improved by esterification modifications. However, the decrease (20-30%) in fibre tensile properties after the treatments was possibly offset by the improvement in fibre/matrix adhesion.