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Preparation of Durable Superhydrophobic Surface by Sol-Gel Method with Citric Acid as Crosslinking Agent

Author: LiuJinYun
Tutor: XingYanJun
School: Donghua University
Course: Textile Chemistry and Dyeing and Finishing Engineering
Keywords: Sol - gel method . Durable water repellent finish Cotton fabric Water glass Citric acid
CLC: TS195.5
Type: Master's thesis
Year: 2011
Downloads: 187
Quote: 0
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Abstract


Water repellent finishing of textiles has a long history, a lot of research or use the repellent agent types. Finishing agent but non-environmentally friendly features, such as water-repellent oil repellent finishing fluorocarbon compounds being a serious challenge to the Environmental Protection Ordinance. Rapidly developed as a safe, environmentally friendly finishing methods, the sol - gel technology in the textile water repellent finishing, and become a research hot one. It can give good cotton fabric water repellent effect, but the durability of water repellent effect is less than ideal. The subject with citric acid as crosslinking agent made a preliminary study to improve cotton fabric by sol - gel method, water repellent finish durability feasibility. Modified with citric acid as a crosslinking agent, prepared by changing the amount of citric acid, containing different amount of free carboxyl groups modified cotton fabric; hydrochloric acid as an acid catalyst, and tetraethylorthosilicate (TEOS) SiO2 sol as precursor. By sol - gel method, water repellent finish a three-stage process (that is, the fabric is first modified by citric acid solution, and then dip rolling SiO2 sol last use of the low surface tension of the substances to finishing) finishing of cotton fabric, to prepare a superhydrophobic surface. Water repellent cotton fabric before washing and after washing the static water contact angle, tricking level, the hydrostatic pressure and the Si content determination of free carboxyl content of the sol - gel method modified cotton fabric water-repellent fabric durability . Using a scanning electron microscope (SEM) to observe the change of the surface morphology before and after soaping citric acid modification fabric sol - gel method after the water repellent finishing. Experimental results show that With the increase of the amount of free carboxyl groups in the cloth, the fabric refused water washability effect better; and after the by the citric change crosslinked to resist the hydrogel membrane did not show off a large area, and still maintain good water repellent effect . This shows that the citric acid can be applied to cotton fabric sol - gel method, water repellent finish, to improve its water repellent durability. In this experiment, inexpensive, common industrial waterglass In order to simplify the process and reduce costs, as the basic raw material, citric acid as an acid catalyst to prepare a stable, homogeneous, transparent silica sol. By measuring the aging process of the sol particle size and sol-gel time, citric acid and electrolyte sodium hypophosphite (SHP) the amount of citric acid - sodium silicate silica sol system. Solid state NMR spectra by FTIR and CP/MAS13C NMR analysis of the mechanism of high-temperature baking after citric acid - sodium silicate sol. The results showed that: With the increase in the amount of citric acid (2 lt; pH-LT;), the gelling time also increases; joint function of sol system electrolyte SHP with citric acid, and with the increase in the amount of SHP gum coagulation time becomes long; after high temperature, citric acid, the carboxyl group may be reacted with silanols to form an ester bond, the carboxyl group is introduced in the structure of silica network. Citric acid - sodium silicate sol-based system using the sol - gel method, water repellent finish a two-step method (first padding citric acid - sodium silicate sol hydrophobic finishing) cotton fabric, Preparation of hydrophobic cotton fabric. Citric acid molecule both as an acid catalyst to prepare SiO2 sol, and used as a crosslinking agent, in a bid to strengthen the force cotton fabric with reject water soluble film to improve the durability of the sol - gel method, water repellent finishing. Experiments by static water contact angle of water spray grade and hydrostatic measurement, analysis and SEM map of citric acid, water repellent finish washability SHP amount of sol - gel method. The experiments showed that, within a certain range, with the increase of the amount of citrate sol - gel method, water repellent finish corresponding increase durability; and SHP presence of citric acid as cross-linking agent to improve the sol - gel method, water repellent durable indispensable in finishing. This indicates that the SHP effect, part of the carboxyl group with a cotton fabric reaction of citric acid molecules forming an ester bond; another part of free carboxyl groups on the surface of the cotton fabric, with silica hydroxyl groups (hydrogen bond and an ester bond effect), to improve the cotton fabric and force between the silica membrane, thereby increasing the sol - gel method of washing performance water repellent finish. Further studies showed that the baking temperature and baking time washing the fabric water-repellent effect. And as the the elevated baking temperature and baking time, a corresponding increase in its water repellent durability. Considering the experiment used 170 ° C, 2min to finishing the fabric to get better water repellent durability can. Sol - gel method to resist the water finishing abrasion performance research found, the SiO2 sol cotton fabric based on TEOS or sodium silicate as the precursor preparation, citric acid crosslinking can improve the wear resistance of the water-repellent fabric . Combined with the friction test the SEM maps and contact angle can be deduced that the number of friction affect the water repellent properties of the fabric was \This topic will be ordinary industrial products cheap water glass instead of TEOS, using water as a solvent to replace conventional ethanol as solvent to prepare nano-silica hydrosol, the choice of the precursor, while saving energy; wide variety of sources citric acid as a cross-linking agent to improve the sol - gel method, water-repellent durability while greatly reducing the cost of production, which will expand the sol - gel technology in textile.

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CLC: > Industrial Technology > Light industry,handicrafts > Textile industry,dyeing and finishing industry > Dyeing and finishing industry > Finishing > Chemical finishing
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