Durable Hydrophobic Finishing Of The Modified Cellulose Fabrics By Sol-gel Method

The technology of the hydrophobic textiles has a long history and a variety of hydrophobic agents were studied and applied. However, non-eco-friendly finishing agents, such as the fluorocarbon-type hydrophobic agents, are faced with serious challenges from environmental protection. As an environment-friendly method, the hydrophobic finishing of cellulose fabrics by sol-gel method is rapidly developed and becomes a hot research in the recent years. Nowaday, the hydrophobicity of cellulose fabrics by sol-gel is excellent. But the washing durability of the hydrophobic cellulose fabrics is unsatisfying. So the feasibility of improving the hydrophobic durability of the modified cellulose fabrics by sol-gel were preliminarily researched in the study.With the hydrolysis of TEOS (Tetraethoxyorthosilicate), purified water as solvent, HC1 as catalyzer, the silica sols was prepared. The cellulose fabrics(pretreated) were treated with the hydrophobic finishing by sol-gel (e.g. the cellulose fabrics was first padded by the sols, then was soaked in hydrophobic agent). The influence of the parameters: the particle size of the silica sols, the concentration of TEOS, pH and temperature in the preparation, on the washing durability were studied. The results showed the washing durability was improved limitedly even if optimizing the preparation process of the silica sols.In order to know about the interaction between the silica sols and the cellulose fabrics, the acetylated cellulose fabrics were treated by the hydrophobic finishing with sol-gel method. The hydrophobicity before and after washing were determined by water contact angles, Si concentratation, SEM and AFM, and the interaction between the silica sols and the acetylated cellulose fabrics were investigated. The results indicated, with the DS (the degree of substitution) increasing, the amount of the hydroxyl in the cellulose fabrics decreases and the durability of the hydrophobic cellulose fabrics also declined. So the cellulose fabrics are combined with the silica sols mainly by the covalent bond or hydrogen bond. The decreasing of amount of the hydroxyl in the cellulose fabrics results in the decline of the durability of the hydrophobic cellulose fabrics. In conclusion, the hydroxyl in the cellulose fabrics is the key factor to affect the bonding force between the silica sols and the cellulose fabrics. the interaction between silica sols and the cellulose fabric should mainly contribute to the durability of the hydrophobicity. To improve the bonding force between silica sols and the cellulose fabric and the washing durability of the hydrophobicity of the modified cellulose fabrics, the cellulose fabrics were modified by polycarboxylic acids as crosslinker. After the hydrophobic finishing by sol-gel, the durability of the hydrophobicity of the modified cellulose fabrics were compared by water contact angles, the height of the hydraulic pressure, the spray test, Si concentratation, FTIR-ATR and SEM. The results indicated that the improvement of the washing durability of the superhydrophobic cellulose fabrics was affected by the structure of the polycarboxylic acids, such as the amount of the carboxyl, the amount of the carbon between the carboxyls and the hydroxyl adjacent to carboxyl, and the durability of the hydrophobic cellulose fabrics modified by different polycarboxylic acids were improved with different degree with following sequence: BTCA>citric acid>the binary carboxylic acids. The hydrophobic durability with BTCA is best, the water contact angle is more than 130°after 30 times washing, the spray rate is 70～80, and the height of the hydraulic pressure is 17.7 cm. The washing durability has a great improvement compared to the hydrophobicity of the native cellulose fabrics.In this study, the research about the interaction between the silica sols and the cellulose fabrics and the usage of polycarboxylic acids as crosslinker to improve the hydrophobic durability of the cellulose fabrics is worthwhile, and will contribute to the application of the sol-gel in functional textile.