Influence of atmospheric helium plasma on the surface energy of jute fibres and the performance of resulting composites

In this work, an atmospheric pressure glow discharge helium plasma treatment was employed to modify the surface properties of jute fibres. The resulting bio-composites showed an increase in flexural properties and interlaminar shear strength (ILSS) compared to composites produced using untreated jute fibres. To understand the reason behind the ILSS improvement, the acid–base properties of jute fibres were determined by contact angle analysis using the capillary rise method. The results were fitted further to van Oss–Chaudhury–Good (vOCG) and Chang–Qin–Chen (CQC) models to determine the Lifshitz–van der Waals (LW) and acid–base components of surface energy. Surface energy determined by the vOCG model revealed that plasma treatment of jute fibre resulted in a 22% increase in total surface energy, a 19% increase in the LW component and a 24% increase in the acid–base component of surface energy. The increase in the acid–base component is due to the significant increase (69%) in the electron-accepting (γ+S) parameter. On the other hand, the CQC model clearly indicates an amphoteric nature of the fibre surface based on opposite signs of the acid and base principal values (PSa and PSb). Overall, the results indicated that increases in both LW and acid–base components were responsible for improvement in the properties of the composites.