Abstract:

Objective Textiles with water repellent function have attracted great attention. At present, the water repellent function is generally achieved by finishing textiles with fluorine-containing chemical agents, but this technique was deemed to cause biological toxicity problems. It research aims to investigate environment-friendly fluorine-free water repellent agent for textiles coating.
Method Two types of stearyl acrylate (SA) copolymer latex (PSA) were prepared by mini-emulsion polymerization of SA with ethyl hexyl acrylate (2-EHA) and cyclohexyl methacrylate (TMCHMA), respectively. These two types of latex were used for fluorine-free waterproof finishing of fabrics. The morphologies of composite latex films were investigated by atomic force microscope. The effects of composite ratio and dosage on the surface structures and waterproof performances of the finished fabrics were studied.
Results To start with, the PSA latex were spin-coated onto glass sildes, and followed by baking at 170 ℃ for 90 s. A relatively smooth surface was observed for latex prepared by copolymerization of SA and 2-EHA, with root mean square roughness (R_q) of only 5.0 nm (Fig. 2) and contact angle(WCA) of 88°. Submicron bulges appeared on the surface of composite latex films containing PSAh obtained by the copolymerization of SA and TMCHMA. Furthermore, with the growth of PSAh fraction, R_q of latex film increased accordingly and attained 13.8 nm as PSAh mass fraction increased to 100%. It led to the water contact angle increasing to 110.0° (Fig. 3). During fabric finishing, the dosage of PSAs-PSAh composite latex was kept at 20 g/L. By adjusting the proportion of composite latex, the contact angle of finished Oxford fabric reached a maximum of 144.8° at the PSAh mass fraction of 40% (Fig. 5). Then, Oxford fabric was replaced by Chun-Ya-Fang with high waving density. When the mass fraction of PSAh in the composite latex is 80%, the water contact angle (WCA) of finished Chun-Ya-Fang reached a maximum value of 152° (Fig. 6). When the dosage of composite latex is increased to 30 g/ L, the WCA of Oxford fabric after finishing were further increased and maintained to be higher than 150° (Fig. 6). The water repellent efficiency of composite latex was higher than either PSAs or PSAh. When attaining the same WCA, the dosage of finishing agent made of solo PSAh was 1.7 times of that of composite latex (Fig. 7). In addition, the composite latex-finished fabric exhibited improved performance of abrasion resistance. After 50 times of abrasion, the static water contact angle of the composite latex-finished fabric retained 148° (Tab. 2). The composite latex-finished fabric exhibited Grade 5 water repellency (Tab. 3) and excellent air permeability (Tab. 4).Conclusion The results showed that the copolymerization of SA and 2-EHA improved the latex film forming capacity, while the introduction of TMCHMA enhanced the shape retention of latex. After the two types of latex were compounded, a micro-nano hydrophobic structure was formed on the surfaces of the finished fabrics, and the waterproof performance of the finished fabrics were significantly improved. The maximum static contact angle reached 152°, and the waterproof grade attained Grade 5. After 50 times of wear resistance tests, the finished fabrics still retained good hydrophobic performance. In addition, the fabric structure exerted a great impact on the water repellency, so the composition of auxiliaries or finishing process should be adjusted during finishing: increasing the amount of auxiliaries, especially the content of PSAh, would improve the water repellency performance. At the same dosage of finishing agent, the best water repellency of fabrics with dense waving structure was generally found at high percentage of PSAh, contrasting that of fabrics with loose structure.

Key words: stearyl acrylate, miniemulsion polymerization, water repellent finish, waterproof, functional textile, fluorine-free water repellent agent