Surface Modification of Plain-Woven Ramie Fabrics Using Bridged Bis (3-Trimethoxysilylpropyl) Amine Silane for Improved Hydrophobicity

Conventional silane treatment can increase the hydrophobicity of natural cellulosic fibers. This report employs a combination of alkali and dipodal silane treatments. Bridged bis (3-trimethoxysilylpropyl) amine (BAS), a dipodal silane, was used instead of regular ones to enhance the hydrophobicity of ramie plain-woven fabrics. Before silane application, alkali treatment conditions’ impact on mechanical properties was optimized using response surface methodology (RSM). The desirability function approach and graphical optimization techniques were employed to find out the optimum condition. The RSM demonstrated that a concentration of 6.11% alkali, a duration of 30 min, and a temperature of 39.10 °C yielded the optimal conditions, resulting in a breaking force of 518.27 N and an elongation of 23.36%. After optimization of parameter, alkali treatment of the fabric was carried out. These alkali-treated fabrics were then bulk-treated with BAS. The Taguchi L9 orthogonal array experimental design was applied to identify a variable that has the highest impact on the hydrophobicity. Furthermore, BAS’s impact on water contact angle (WCA), surface morphology, and thermal properties was investigated. Alkali-treated ramie fabrics absorb water due to hemicellulose and lignin removal. However, BAS treatment resulted in a hydrophobic ramie fabric surface, as the combined alkali and BAS-treated fabrics exhibit a WCA greater than 94°, reaching 113.85°. According to thermo-gravimetric analysis, combined alkali and silane treatment improved the degradation temperature of fabrics to 403.25 °C. This improvement is attributed to the formation of six, rather than three, Si–O bonds on the ramie fabric surface.