Influence of alkali treatment on the interfacial properties of bamboo/polyester composites

Background: Natural fibres are getting substantial attention as reinforcement in polymer composites. However, they are commonly recognised to have poor compatibility with polymers. Hence, it is important to enhance the interfacial bonding of natural fibres. Recent patents have highlighted several alternatives to improve the interfacial characteristics. Objective: In this study, the interfacial shear strength of untreated and 10wt% sodium hydroxide (NaOH) treated bamboo fibre reinforced polyester composites was investigated. Method: The bamboo fibre length was fixed at 7mm in both cases. The interfacial shear strength was measured through single fibre pull-out test (SFPT) and subsequently analysed using Weibull distribution plot. Results were also compared with the data from literature. Finally, scanning electron micrographs (SEM) were captured to analyse the debonded surfaces of both matrix and fibre. Results: Results showed that the interfacial shear strength of the treated fibre was improved by almost three fold higher than the untreated fibre. In addition, Weibull analysis revealed that the Weibull moduli were similar for both untreated and treated fibres. This suggested that surface impurities were formed on the treated fibre due to the damage induced by sodium hydroxide. Furthermore, scanning electron micrographs showed that alkalisation has modified the fibre surface morphology and improved the overall surface quality for better interfacial bonding. Conclusion: In conclusion, alkali treatment is a potential method to improve the interfacial characteristics of bamboo fibre in unsaturated polyester. Recent patent suggested that coating with bacterial cellulose is a green technique for better interfacial bonding behaviour