Abstract:

Objective Fabrics with water-repellent finishing have been extensively favored by consumers as one of the most widely used functional fabrics, and hydrophobic coatings and their applications prospects attract interests from both the academic and industrial comunities. However, their application is hindered by some major bottlenecks, especially the poor durability. Therefore, a method for preparing hydrophobic coatings with excellent mechanical stability is urgently necessary.

Method To tackle the poor durability of water-repellent finishing fabrics, this study innovatively introduced low surface energy polysiloxane segments and long carbon chain hexadecyl at the same time. A novel durable water-based hybrid fluorine-free water-repellant finishing agents (NSW) were prepared by amino modification of silica sol emulsion to enhance the interfacial interaction between the organic and inorganic components. This modification corresponded to the long-chain alkyl silane modified sol emulsion and polysiloxane modified waterborne polyurethane emulsion respectively. The specific methods used were described below. A polysiloxane modified polyurethane prepolymer (SiWPU) was synthesized through the polyaddition reaction of polydimethylsiloxane (PDMS), polyethylene glycol (PEG), dimethylol propionic acid (DMPA) and isophorone diisocyanate (IPDI). A method of the long-chain alkyl silane and amino modified sol emulsion (Si-NPs) was provided through the hydrolysis polycondensation reaction of hexadecyl trimethoxysilane (HDTMS), silane coupling agent (KH-550) and tetraethyl silicate (TEOS). Si-NPs were added drop by drop in the emulsification process of Si-WPU, silica nanoparticles were adhered to the polyurethane chain segment taking advantage of the difference in the rate of isocyanate group react with amino and hydroxyl group, and isocyanate group exhibits a higher rate of reaction with amino compared with hydroxyl group.

Results The chemical composition of Si-NPs and NSW were investigated using Fourier transform infrared spectroscopy. The most stable emulsion was achieved when KH-550 mass fraction was 1.5% (Si-NPs-1.5 and NSW-1.5), and the stability analysis of Si-NPs and NSW-1.5 were demonstrated using particle size tester and Zeta potential analyzer. In addition, the research also focused on the hydrophobic effects of the amount of aminosilane coupling agent in the silica sol. Baking temperature on the property of finished polyester/cotton fabric was also discussed in detail, and the hydrophobic performance and the wash resistance on the surface of finished polyester/cotton fabric were also investigated. It was found that when the mass ratio of KH-550 was 1.5% and the baking temperature remained at 160 ℃, NSW formed a complete water-repellent membrane. Under the conditions of these application environment on the surface of treated fabric with water contact angle (WCA) of 131.8°, the WCA of the treated fabric dropped by only 2.8°after 20 rubbing cycles and exhibited good washability. The surface morphology of the treated polyester/cotton fabric before and after washing was observed in order to study the water wash resistance on the surface of finished polyester/cotton fabric more intuitively, and the results of SEM images showed that micro-nano rough structures existed on the surface of finished polyester/cotton fabric. Additionally, the repellent effect of the treated fabric on different liquids was also studied to demonstrate the above viewpoint.

Conclusion It is confirmed through the research that when the mass ratio of KH-550 is 1.5% and the baking temperature remains at 160 ℃, the surface of the finished fabric exhibits the best water resistance performance. In view of the poor durability of finishing agents, a method for preparing fully aqueous and organic-inorganic hybrid fluorine-free water-repellant finishing agents was identified, which is to combine the long-chain alkyl silane modified sol emulsion and polysiloxane modified waterborne polyurethane emulsion for the stable preparation of waterproofing agents.

Key words: fluorine-free water-repellant finishing agent, water-repellant finishing, organic-inorganic hybrid, functional textile