With the improvement of people's living standards, outdoor activities are increasing. Due to the complex and changeable outdoor environment, the demand for functional textiles is constantly rising. Among them, textiles with UV resistance and heat insulation functions are an important type. Such textiles achieve their functions by applying UV-resistant and heat-insulating coatings. 1 Coating finishing 
Coating finishing refers to a surface processing technology in which one or more layers of high-molecular film-forming substances are evenly applied to the surface of fabrics to endow them with different functions. Coating can change the appearance and style of fabrics and enhance their functionality. Anti-ultraviolet and heat-insulating coatings are among them. 
The types of coating agents vary, and so do their properties. From the perspective of chemical structure, common coating agents include polyvinyl chloride resin (PVC), polyacrylate coating agent (PA), polyurethane coating agent (PU), natural rubber and synthetic rubber coating agents. According to the medium used, they can be classified into solvent-based and water-dispersible types. Among them, PA and PU are two commonly used coating agents. The main methods of fabric coating include direct coating, transfer coating, coagulation coating, foam coating and lamination, etc. The main problem with current coating finishing is that the majority of the dispersing media used during the finishing process are organic solvents, which have disadvantages such as flammability, toxicity and high cost. The development of coating agents with water as the dispersing medium is the current development direction. 
2. Anti-UV and Heat Insulation Principles 
When a beam of light shines on fabric, three phenomena often occur: absorption, transmission and reflection. That is, part of it is absorbed by the fabric, part is reflected on the fabric surface, and the rest passes through the fabric. The principle of UV resistance is to add nano-powder materials with UV resistance to the coating and finish the fabric. When light radiates onto the fabric, a small part passes through the fabric, and the vast majority is reflected or absorbed by the nano-powder materials. The heat insulation mechanism can be divided into barrier type, reflection type and radiation type. Among them, the reflection type has been studied the most, and its mechanism of action is to reflect the radiant energy in the visible light and near-infrared light regions. 
3 Preparation of Anti-Ultraviolet Coatings 
Nanometer TiO2 is a kind of white powder that is non-toxic, low-cost, abundant in source, highly chemically and photostable, with strong light scattering ability and good ultraviolet shielding property. As functional particles, it can be adhered to fabrics through coating finishing, thereby enhancing the UV resistance and heat insulation performance of the fabrics. 
Nanometer ZnO is another kind of nanometer powder material that has been widely studied and applied, and is currently widely used in sunscreens. Tao Ye prepared nanometer ZnO sol and applied it to the anti-ultraviolet finishing of nylon fabrics. The experiments showed that the anti-ultraviolet performance of the treated fabrics was significantly improved. 
Research and application of SiO2 nano-powder materials are relatively rare, and they are generally composite powder materials. Weibin Bai et al. prepared a lacquer phenol formaldehyde polymer/multi-hydroxy acrylic resin/SiO2 nano-composite material through the sol-gel method. After a 1000-hour anti-ultraviolet test, the results showed that the prepared nano-composite material had good anti-ultraviolet performance, and when the SiO2 content reached 5wt.%, the nano-composite material exhibited the best anti-ultraviolet property. 
Although these nano-powder materials have been extensively studied, they still have the drawback of easy agglomeration during use, which prevents the full utilization of the properties of nano-particles. If the surface of the nano-particles is modified, they will be less prone to agglomeration during use, which can improve the uniformity of the composite coating and enhance its UV resistance and heat insulation performance. 
4 Preparation of Thermal Insulation Coatings 
Chen Kening et al. prepared high-performance heat-insulating coating fabrics by using polyurethane as the adhesive and TiO2 as the functional particles through the coating method. The results showed that the heat-insulating performance and mechanical properties of the coated fabrics were both good. Wang Kelin et al. prepared TiO2-coated fabrics with good heat-insulating performance by using TiO2 as the functional particles and the coating method. The results indicated that the heat-insulating performance of the fabrics was significantly improved after coating. Li Na et al. prepared monodisperse spherical SiO2 particles and applied them to the infrared reflection heat-insulating finishing of cotton fabrics through the pad-dry-cure process. The samples were characterized by FT-IR, TEM, etc. The results showed that the temperature rise rate of the finished fabrics under infrared radiation was slow, and the surface temperature was lower than that of the unfinished fabrics, endowing the fabrics with heat-insulating and cool properties. 
Nanoparticles added in the thermal insulation coating also have the problem of agglomeration. To improve the thermal insulation performance of the coating and alleviate the agglomeration of nanoparticles, many researchers have conducted some studies. Lu Bin et al. prepared a transparent thermal insulation coating of SiO2 aerogel modified with a stabilizer. The experiment showed that the SiO2 aerogel particles were uniformly dispersed and had a good thermal insulation effect. Wang Kelin et al. modified the surface of TiO2 with sodium dodecylbenzene sulfonate through experiments to improve the dispersion and stability of TiO2 powder in polyurethane thermal insulation coatings. The results confirmed that the dispersion stability of the modified TiO2 in polyurethane thermal insulation coatings and the thermal insulation performance of the coated fabric were improved to varying degrees. 
Aerogel is regarded as one of the most promising high-performance thermal insulation materials. Compared with traditional thermal insulation materials, it shows remarkable thermal insulation performance due to its thermal conductivity dropping to 13 mW·m-1·K-1. However, the inherent brittleness of aerogel and the high infrared transmittance of SiO2 aerogel in high-temperature environments limit its application range. Incorporating light blockers into aerogel can improve these situations. 
5 Preparation of Anti-Ultraviolet and Heat-Insulating Coatings 
Fan Lihong et al. used nano-inorganic oxides (TiO2 and ZnO) to conduct anti-ultraviolet composite coating finishing on soy protein fabric. Performance tests indicated that the finished soy protein fabric not only had excellent anti-ultraviolet function but also had excellent anti-infrared and heat insulation effects. Wang Shuzhong et al. studied the research on the composite technology of inorganic nanoparticles and styrene-butadiene latex. The results proved that both nano-CaCO3 and nano-ZnO had heat insulation functions, and ZnO also had anti-ultraviolet aging function. Sheng Zhenhong et al. prepared an environmentally friendly coating material with high efficiency in blocking infrared and ultraviolet radiation through the liquid phase method. When applied to glass, the ultraviolet shielding rate of the film layer was measured to be 75.7%, and the infrared blocking rate was 92%.