Study On Preparation And Properties Of Thermoregulatory Fabric Based On Phase Change Materials

Phase change material can store light and heat in the surrounding environment through energy conversion and combine with textiles to give them a temperature regulation function.However,the phase change material has a leakage problem during the phase transition process,which limits its direct application.The phase change material must be encapsulated and fixed into a composite phase change material before it can be used.The temperature at which the human body feels comfortable is around 30.0?.This topic uses n-octadecane or disodium hydrogen phosphate dodecahydrate with a melting point of around 30.0?as the phase change material,and chooses diatomite,halloysite,and cellulose sponge.And bacterial cellulose membrane,as encapsulation materials,prepare composite phase change materials with shape stability and direct application.The prepared composite phase change material is combined with textiles in different ways.To obtain heat-regulating textiles with different functions,the specific content can be divided into the following four parts:(1)Diatomite-based composite phase change material and its thermal insulation coating fabric:To smoothly immerse n-octadecane liquid into the pores of diatomite about300 nm,a microemulsion vacuum immersion demulsification method is proposed for the first time.The n-octadecane microemulsion with a particle size of less than 200 nm can be immersed in the pores of acid-treated diatomite under vacuum,and an alcohol solvent was used to drop the n-octadecane microemulsion into the mixture to demulsify the n-octadecane microemulsion.N-octadecane was adsorbed in the pores of diatomite by capillary force,and maintains a stable shape and no phase leakage at 50°C.After acid treatment,the average pore diameter of diatomite changed from 13.35 nm to 25.54 nm.Among the composite phase change materials prepared,the quality of the phase change materials accounted for51.7%higher than that of the original diatomite.The latent heat energy of the diatomite-based composite phase change material was 34.69 J/g,and it was mixed with water-based polyurethane and coated on the surface of the cotton fabric.The heat transfer coefficient of the obtained thermal insulation fabric was 50.74.Measured by the flat heat preservation method,its heat preservation rate was 171.1%higher than that of cotton fabrics,and the instantaneous warmth and coldness were improved by 6.4%.The internal temperature of the bottle body covered with the thermal insulation fabric was 7.0%higher than that of the uncoated bottle body,showing the thermal insulation effect.(2)Halloysite-based composite phase change material and its moisture-absorbing,breathable light-heat conversion coating fabric:The diameter of halloysite is too small,the halloysite can be treated with sulfuric acid to increase its specific surface area by 91.06%.Or graft modification of halloysite to form a larger gap,increasing the average pore radius by 88.54%.The treated halloysite and n-octadecane are made into a composite phase change material through a vacuum impregnation method.The two modified halloysites had similar maximum loading capacity to n-octadecane,but the composite phase change material prepared by grafting modified halloysite had better shape stability,and the latent heat energy was 64.72 J/g.The composite phase change material was mixed with polyurethane,and the fabric prepared by wet coating can achieve 32.4%photothermal conversion efficiency and5.97%air permeability.At the same time,the coating surface showed a super-hydrophobic effect,with a contact angle of 121.12°.The uncoated surface can absorb 5?L of deionized water within 9 seconds,which had a good moisture absorption effect.Under sunlight,the surface temperature of the photothermal conversion fabric was 15.2?higher than that of the cotton fabric.After 1200 s of light,the temperature of 25 m L of deionized water in the colorimetric tube covered by the coated fabric increased by 1.1?compared with the uncoated temperature.Through the thermal performance test of the iodine tungsten lamp,it was found that the surface temperature of the photothermal conversion coating fabric was19.3%higher than that of the cotton fabric,and it had heat storage properties and can be delayed for 410 s.(3)Cellulose sponge composite phase change material and its interlayer thermal insulation fabric:The mass ratio of cellulose nanocrystals and vinyltrimethoxysilica was1:1,and the prepared sponge had a uniform pore structure with a porosity of 99.03%,With a density of 0.012 g/cm~3,it can bear 1900 times of its own gravity.When the mass ratio of n-octadecane to disodium hydrogen phosphate dodecahydrate was 2:3,it can be emulsified by Span 80 to produce an emulsion with excellent stability,which can be immersed in a cellulose sponge to make a composite phase change material by the shaking dipping method.The composite phase change material had very low phase leakage after heating at 50°C for30 min.It is stitched by cotton fabric to make a sandwich insulation fabric.It can be irradiated with a tungsten iodine lamp for 900 s to cool down by 17.7%compared to cotton fabric.Compared with cotton fabric,the temperature was reduced by 18.2%when exposed to sunlight for 1800 s.(4)Flexible cellulose membrane composite phase change material and composite thermoregulatory fabric:The bacterial cellulose membrane can be freeze-dried to form a porous material with a thickness of 0.45 mm and a 3D network structure.The composite phase change material was prepared by immersing n-octadecane into the bacterial cellulose membrane by the vacuum dipping method.The latent heat energy was 212.70 J/g,and the mass of the phase change material accounted for 84.9%.No phase leakage after heating at50°C.To improve the flexibility and compression performance of the composite phase change material,polydimethylsiloxane(PDMS)was used to encapsulate it,which can be folded 180°and withstand a pressure of 277.4 k Pa.In an environment of 10°C?40°C,the wrinkle recovery angle of the flexible temperature-regulating film was between149.8°?157.2°.In addition,the phase change with the original cellulose film has light transmittance,and the latent heat energy was only reduced by 7.1%after 100 thermal cycles.The sunshine test found that the temperature in the space covered by the material was 1.8°C lower than that of the original fabric.When preparing the flexible light-transmitting temperature-regulating film,the PDMS coated composite phase change material was covered on both sides of the polyester-cotton blended fabric,and then cured at a high temperature to form a composite thermoregulatory fabric.Compared with the original fabric,the composite thermoregulatory fabric can delay the temperature drop by 310 s during the cooling process after heating at 50?for 10 min.