Structure Design,Preparation And Properties Reaearch Based On The Thermal Insulation Polypropylene Fibers

Cold is one of the natural challenges that threaten human survival.Generally speaking,there are two ways for people to resist the severe cold:putting on heavy clothing or turning on heating equipment.However,with the improvement of living standards and the transformation of human ideology,people tend to pursue lightweight thermal clothing and heating methods with lower energy consumption.Polypropylene(PP)fiber with the advantage of low density has become an ideal material for preparing lightweight thermal insulation textiles.In this paper,from the four perspectives of inhibiting heat conduction,limiting heat convection,using thermal radiation,and introducing Joule heat,PP fibers were used as the base material to control the material performance and design structure of fibers,yarns and textiles,to further improve the warm-keeping capacity.The details are as follows:(1)Adjust the fiber thermal conductivity from the perspective of heat conduction:The thermal conductivity of the PP fibers is adjusted from two aspects.One was to use a self-made heat drawing equipment to adjust the axial and radial thermal conductivity of the PP fibers;the second was to compare the thermal conductivity of PP fibers with different crosssectional shapes.And fiber thermal conductivity was anisotropic,so its axial and radial thermal conductivity were analyzed separately.The heat drawing process increases the axial and radial thermal conductivity of the PP fiber,and the axial thermal conductivity increases faster than the radial thermal conductivity.This was because the thermal drawing process makes the crystal orientation more perfect and the phonon transmission speed is increased.The hollow cross-section PP fiber had a lower thermal conductivity,which was due to the low thermal conductivity of still air in the hollow fiber,which reduces the overall thermal conductivity of the fiber.(2)Design the yarn structure from the perspectives of heat conduction,heat convection,and heat radiation:a bionic yarn with PP hollow fibers core layer and polyacrylonitrile(PAN)nanofibers skin layer was designed by a self-improved conjugate electrospinning device.By adjusting the parameters,the yarn had a porosity of about 62%and a stable multilayer fiber layer structure.Compared with PP hollow fiber bundles of the same diameter,the composite bionic yarn had better thermal insulation and moisture conductivity.It had a temperature difference of 4.9? on the skin and yarn surface.Compared with the PP textiles,the textile woven by the yarns also had excellent heat insulation performance.The air permeability was slightly reduced,and the moisture permeability was slightly improved.(3)Surface structure design of the textile from the perspective of thermal radiation and electric heating:polydopamine(PDA)was used to modify the PP textile,and silver nanowires(AgNWs)were combined with it to prepare AgNWs composite textiles with the ability to reflect heat radiation and electric heating.Compared with PP textile,the AgNWs composite textile had a radiant heat reflectivity of more than 50%,and its thermal insulation performance was excellent.It also had excellent electric heating performance.Under a heating voltage of 5 V,the temperature of the textile can be increased to 39.1? within 58 s.The presence of PDA and AgNWs had little effect on the air permeability of the textile,and the moisture permeability was slightly improved.