Optimization of surface treatment in Calotropis Gigantea (CG)-fibre yarn by simple techniques and characterization of CG fibre yarn reinforced laminate

Abstract

Calotropis Gigantea (CG) is a shrub plant that grows rampantly in South Asia. Here we report the development of CG bast fibre yarns, which could yield replacements for artificial fibres in engineering applications. Most of the researchers concentrated only in the short form of natural fibres, this leads to dropping the fibre reinforcement in continuous and lengthy products. An attempt has been made in this research by taking CG fibre in the form of twisted yarn as reinforcement. The surface treatment is done to enhance the properties of the CG fibres and to reduce hydrophilic and hygroscopic behaviour using NaOH (aq.). Determining the appropriate NaOH concentration in the treatment solution is essential to reduce the hydrophilicity of the fibres while retaining its mechanical properties. Generally optimised NaOH concentration found by completing fibre characterization, which is a very lengthy and time-consuming process. In this research work, the optimum concentration of NaOH found by a quick and short process using simple techniques. Two techniques were used such as Contact angle measurement of fibre surface and microscopic observation of xylem structure to find an optimum concentration of NaOH in the aqueous solution. On treated CG fibres, the contact angle is found to be as high as 112° for 4 wt.% NaOH (aq.) concentration; indicating that the treatment renders the fibre hydrophobic and the observation of xylem structure (voids) confirms in a minimum amount in the same 4 wt.% NaOH treated fibre. The mechanism involved is rationalized using infrared/vibrational spectroscopy based measurements of untreated and treated sampled. The orientation of the fibre helps with optimization of the properties. The elastic modulus (measured as per ASTM standards) obtained are 4.18 GPa (along the fibres) and 3.05 GPa (perpendicular to the fibres).

Keywords

• Natural fibre yarn
• Modulus
• Alkali treatment
• Contact angle measurement
• Unidirectional orientation
• Fibre weight ratio