The self-cleaning textile technology is based on the self-cleaning principle of lotus leaf, which makes the textile have the self-cleaning effect similar to lotus leaf, and can effectively prevent accidental contamination in life. Its core technology is to have the "Three Prevention" function without affecting the moisture absorption and permeability of the fabric itself. The development of self-cleaning functional textiles can not only alleviate the environmental and energy problems caused by washing, but also effectively shield and digest various environmental pollutants such as bacteria, viruses, pesticides, stains and so on, so as to avoid the harm of these pollutants to human body through skin or respiratory tract. It can be widely used in daily clothing, biochemical protective clothing, medical care, environment, farm, etc Military and other fields. There are two ways to obtain self-cleaning function: one is to form superhydrophobic surface, the other is to form photocatalytic surface.
Superhydrophobic surface technology
According to the principle of surface dynamic wetting, the water droplets on superhydrophobic surface are in Cassie state. In the Cassie state, the shape of the droplet is close to that of a sphere under the action of surface tension, and the motion behavior of the droplet on the superhydrophobic surface is similar to the rolling of a sphere. At this time, when the size of the impurity on the hydrophobic surface is smaller than the size of the water drop ball, the adhesion (surface tension) of the water drop to the impurity particles is much greater than that of the hydrophobic surface to the impurity particles, so the impurity can be absorbed on the surface of the water drop and gradually wrapped in the inside of the water drop, and the impurity particles will move in the inside of the water drop and move with the movement of the water drop, So as to achieve the removal of impurities.
Based on the bionics principle to construct the surface structure of materials and obtain the bionic self-cleaning surface is the main method for the preparation of self-cleaning functional textiles. Many animals and plants (such as lotus leaves, rice leaves and butterfly wings) have superhydrophobic and self-cleaning effects. Using lotus leaves or petals as templates for structure replication, polymer films with reverse (similar) surface structure of lotus leaves or petals have good self-cleaning effect. The results show that the "lotus leaf effect" can be achieved by depositing carbon nanotubes (CNTs) on the rough surface of cotton fabric.
Superhydrophobic structures of butterfly wings and water Striders
Another superhydrophobic method is to modify or coat the surface with low surface energy materials containing fluorine and silicon groups. For example, nanosphere technology can be applied to the water repellent finishing of silk and wool fabrics by fluorocarbon finishing of cotton and natural fiber blended fabrics.
Thirdly, nanotechnology can be used for superhydrophobic treatment of fibers and fabrics. For example, mincor TX TT finishing technology simulates the microstructure of lotus leaf, embeds nanoparticles into polymer matrix through finishing process, and endows the finished fabric with durable nanostructured surface; The research team of Suzhou Institute of nanotechnology and nanobionics, Chinese Academy of Sciences, has constructed a multi-stage micro nano composite structure of multi walled carbon nanotubes (MWCNT) / thermoplastic elastomer (TPE) composite superhydrophobic intelligent coating, which has both superhydrophobic and excellent strain sensing properties, and can effectively resist the interference of water, acid, alkali, sweat, etc.
The surface morphology (a, b), the optical photos (c) and the cross-section morphology (d) of the intelligent coating after the pretreatment, alkali treatment, acid treatment and UV treatment
Photocatalytic surface treatment technology
Self cleaning surface technology based on the principle of photocatalysis is a technology using new composite nano high-tech functional materials. At present, the most used surface nano materials are nano-TiO2 photo induced thin films. Under a certain wavelength of light irradiation, the photocatalyst nanoparticles are stimulated to form electron hole pairs, in which the electrons have strong reducibility, on the contrary, the holes have oxidation. Therefore, photocatalyst nanoparticles have strong oxidation-reduction effect under light irradiation, which can decompose many refractory organic compounds, destroy various pollutants on the surface of photocatalyst, inhibit the growth of bacteria and the activity of virus, and achieve the purpose of self-cleaning.
In 1997, the amphiphilic principle of nano-TiO2 film was first reported on nature, which opened up the application of TiO2 in the field of self-cleaning. Since then, the research achievements in self-cleaning of organic polymer fibers have also emerged in an endless stream. The research of Hong Kong Polytechnic University and Australia shows that anatase nano-TiO2 film is prepared on the surface of polyester and cotton fabrics. The cotton fabrics treated by this technology can degrade the surface stains, such as red wine stains, after photocatalytic oxidation; The molecular biology engineering center of the U.S. Navy laboratory adds enzymes to the film to effectively degrade chemical toxins, controls the thickness of the film to 500 nm, and then finishes the film on textiles. The enzymes added to the film can quickly neutralize toxins and have no harmful residues, which can be applied to military and civil protective clothing finishing; Researchers from the Royal Melbourne Polytechnic University deposit 3D copper and silver nanostructures on the cotton yarn, and then weave them into a fabric. When the fabric is exposed to light, the nanostructures absorb energy to excite the electrons in the metal atoms, and then decompose the dirt on the surface of the fabric, realizing self-cleaning in about 6 minutes.
Surface structure of micro metal
Fibers and fabrics with self-cleaning properties have a very wide application prospect in daily life and industry. However, the research status of self-cleaning fibers and fabrics shows that there are still many key problems to be further researched and developed. For example, the preparation methods of superhydrophobic self-cleaning surfaces mostly require complex design, fine control technology or expensive fluorosilicone compounds; There are some problems in photocatalytic self-cleaning surface technology, such as insufficient fastness of inorganic TiO2 particles to fiber, easy to fall off, affecting the handle of fiber, and difficult to disperse evenly on the surface of fiber. Therefore, new ideas are needed to develop self-cleaning methods with high performance and low cost for fiber materials.