Comparison of Effects of Alkali Treatment on Flax Fibre Reinforced Polyester and Polyester-Biopolymer Blend Resins

In this study, flax fibres were treated initially with a 2.5, 5, and 7% of sodium hydroxide (NaOH) solution at room temperature for one hour. Among different treatments, fibres treated with 2.5% alkali solution showed optimal properties. Hence, for further studies, all flax fibres were treated with 2.5% solution of alkali solution, but at different temperatures. In the next phase of study, biocomposites were prepared by immersing fibre mats in resin bath and compression moulding using a hot press. Two polymers: polyester and a polyester-biopolymer blend, Envirez® 1807 were used as matrices. Moisture absorption and flexure tests were conducted on the composites. It was determined that composites with treated fibres showed reduction in moisture uptake compared to those with untreated fibres. Composites with alkali treated fibres showed an increase in flexural properties as well as storage modulus which was attributed to effects of chemical treatment. Composites made using Envirez® 1807 which has about 22% of natural polymer showed comparable properties with those made using polyester resin system.