Preparation,waterproof And Moisture-permeable Properties Of Electrospun Polyurethane/silica Microporous Film

The waterproof and moisture permeable microporous film has the structural feature of allowing water vapor to pass through but not water droplets to enter.In recent years,it has been favored by many researchers and is widely used in sportswear,tents,filtration and the like.Polyurethane（PU）has a soft-hard segment co-embedded structure and excellent physical and chemical properties.Microporous membranes prepared by electrospinning technology using PU as a raw material have a high research value in waterproof and moisture permeable fields.In this paper,superhydrophobic silica particles（SNPs）were first added to PU spinning solution to improve the hydrophobic properties of PU microporous film,and the effects of different concentrations of SNPs on the waterproof and moisture permeability of PU/SNPs microfiber microporous films were investigated.The results showed that when the concentration of SNPs was 9%,the fracture stress was 4.16 MPa and the broken strain was 184%.Compared with the pure PU film,the broken strain of the PU/SNPs microporous films was reduced by22.60%,indicating that it had a better dimensional stability.At the same time,due to the introduction of SNPs,the surface energy of PU microporous film was reduced,and the surface had a rough micro-nano structure.The prepared PU/SNPs microporous films were endowed with the static water contact angle of 131.00°,the hydrostatic pressure achieves to 6.40 kPa,and the air permeability amount of it is up to 33.40 mm/s and the moisture permeability reach up to 8065g/（m²·24h）.In order to further improve the hydrophobic properties of the PU microporous film,tetraethyl orthosilicate（TEOS）and SNPs were added to the PU solution,and the PU/TEOS/SNPs microporous films were obtained by electrospinning.Polytrimethoxysilane（HDTMS）was used to treat the microporous films to obtain a polyurethane/silica（PU/SiO₂）microfiber microporous films.The effects of different concentrations of TEOS on the waterproof and moisture permeability of PU/SiO₂ microporous films were studied.The results showed that when the concentration of TEOS was 6%,the static water contact angle of the PU/SiO₂microporous film was increased to 138.81°,the hydrostatic pressure reached 12.93 kPa,and the pore diameter decreased（the maximum pore diameter was 4.65μm,average pore diameter was1.36μm）,and the porosity was high simultaneously（porosity was 62.59%）,making the microporous film maintained good moisture permeability（air permeability was 11.10 mm/s,moisture permeability can reach 7290 g/（m²·24h））.Due to the existence of inter-fiber adhesion structure,the microporous film had better mechanical properties,and the fracture stress can reach 3.95 MPa.Finally,a waterproof and moisture-permeable laminated fabric was prepared by hot-pressing a PU/SiO₂ microfiber microporous film obtained by TEOS concentration of 6%and a polyester base fabric.The results showed that the thickness of the composite laminate fabric was 190μm,the weight of the square meter was less than 120 g/m².So the human body were comfortable to wear.Moreover,the pore diameter of the composite laminate fabric were lowered,and the hydrostatic pressure can be up to 23.50 kPa.At this time,the air permeability of the laminated fabric was 1.34 mm/s,and the moisture permeability was 5190 g/（m²·24h）.After a simple ultrasonic cleaning,the static water contact angle of the laminated fabric did not change much,indicating that the waterproof performance of the laminated fabric was durable.