Controllable Preparation And Properties Study Of Washable Ultrafine Fiber Sponge For Warmth Retention

Cold has always been one of the important factors affecting human health.In the evolution and development,human beings have learned to obtain animal and plant fiber materials such as hemp,cotton,wool and silk from nature to keep the human body warm.These natural fiber materials can fit the human body well,and have excellent warm-keeping effect,which is non-toxic and harmless.However,when used for a long time,they are prone to hardening,moth-eaten and mold breeding,which reduces their warm-keeping effect.In the last century,chemical fiber thermal insulation material developed rapidly,which has the advantages of insect resistance and mildew resistance.However,due to its coarse fiber diameter,it is difficult to further improve its thermal insulation performance.In recent years,various new thermal insulation materials have been put on the stage,mainly including coated composite materials,heat conversion materials and superfine fiber materials.The raw materials and preparation process of coating composite materials and thermal conversion materials are limited to some extent,so they cannot be popularized in a large scale.Ultrafine fiber materials have the advantages of high porosity,minor diameter and high specific surface area,which can store a large amount of still air and effectively isolate heat loss,and will be the research focus of efficient warmth retention in the future.Electrospinning technology stands out among many methods for preparing ultrafine fiber materials because of its obvious advantages.However,the existing electrospun ultrafine fiber materials are mostly two-dimensional membrane structures,and their application in the field of thermal insulation is limited.Although a few researchers have developed fluffy electrospun ultrafine fiber materials,their structural stability is poor and they are easy to collapse,and they cannot withstand compression,stretching and washing.Therefore,it is of far-reaching significance to develop ultra-fine fiber high-efficiency thermal insulation materials with stable fluffy structure,excellent mechanical properties and washing resistance.In this paper,firstly,polyether sulfone（PES）and polyurethane（PU）were used as polymer raw materials,and ultrafine fiber sponge PES/PU with stable fluffy structure were prepared by electrospinning.Its morphology,structure,and properties were studied under varying relative humidity conditions,and 90%was determined as the best environmental relative humidity.The average fiber diameter of PES/PU is 3.3μm,the average pore diameter is 9.9μm,the porosity is99.8%,and the bulk density is 3.4 mgcm^-3.It has good mechanical properties and stable fluffy structure.The maximum compressive stress is 203.4Pa at 60%fixed compressive strain,and the original state can be restored when the external force is removed.At the same time,it has excellent thermal insulation performance,and its thermal conductivity is 21.4m W m^-1K^-1.Secondly,FPU with low surface energy was introduced into the spinning solution to improve the hydrophobic property of ultrafine fiber sponge.At the same time,the influence of different contents of FPU on the morphology,structure and properties of the material is explored,and it is concluded that the introduction of FPU will not destroy the morphology,structure and properties of the materials,and the optimal addition amount of FPU was finally determined to be 12wt%.The structural characteristics,mechanical properties and thermal insulation properties of PES/PU/FPU fiber sponge have little change compared with those without FPU.Its static contact angle is 141.2°,and it has excellent hydrophobic properties.Then,the cross-linking agent isocyanate（BIP）was introduced into the ultrafine fiber batt to further enhance the mechanical properties of the materials.The material’s morphology,structure,and properties were studied at varying BIP content levels,and the optimum addition amount of BIP was determined to be 16wt%.The mechanical properties,thermal insulation and washing resistance of PES/PU/FPU/BIP were further studied.The results showed that after 1000 compression cycles（ε=60%）,the maximum compressive stress and compressive modulus of PES/PU/FPU/BIP fiber sponge could be kept above 75%of the initial value,and the compressive fatigue resistance was excellent.After compression（ε=60%）at low temperature（-50℃）,it can recover to its original state without obvious plastic deformation.After 1000 tensile cycles（ε=20%）,its tensile stress is 16.0k Pa,and its tensile fatigue resistance is excellent.At the same time,the thermal conductivity of PES/PU/FPU/BIP is 25.3m W m^-1K^-1 and 25.7m W m^-1K^-1,respectively.In addition,the morphology,structure and properties of PES/PU/FPU/BIP have little change after 10 cycles of washing,and they have excellent washing resistance.Finally,the structure and properties of the ultrafine fiber thermal wadding PES/PU/FPU/BIP were compared with those of the thermal wadding materials on the market.The results indicated that the fiber diameter,average pore diameter and thermal conductivity of PES/PU/FPU/BIP were much smaller than those of the thermal wadding materials on the market,and the fluffy structure and thermal properties of PES/PU/FPU/BIP changed the least after 10washing cycles,showing its great development potential in cold and thermal insulation applications.