Study On Functional Films Of Electrostatic Spun Polyurethane Waterproof And Permeable Nanofibers

In this paper,the polyurethane nanofibrous membrane was prepared by electrospinning,to research and realize the function of waterproof and moisture permeability.In order to study the effect of solvents on polyurethane nanofibrous,the solution properties of the solutions,such as solubility parameter,solvent permittivity and dipole moment were studied by thermodynamics and polymer solution theory.These properties will further affect the solution viscosity,conductivity,polymer-solvent interaction and surface tension.The effects of solvents on the structure and mechanical properties of the nanofibrous membranes were investigated by SEM and mechanical tensile tests.SEM images showed that when the DMF / acetone volμme ratio is 75 / 25,the results show that the nanofibrous are the most regular and the most uniform,and the nanofibrous are narrower and the diameters of fibers are narrowest.The stress-strain curves of the nanofibrous membrane showed that the stress and strain of the nanofibrous membrane increased with the decrease of DMF in the mixed solvent.When DMF / acetone volμme ratio is 75/25,the stress and strain were 6.45 MPa and 272.5% respectively.The diameters of polyurethane nanofibrous had a great influence on the waterproof and moisture permeability of the nanofibrous membrane.In this paper,the diameter of polyurethane nanofibrous was controlled by varying the spinning solvent,the spinning voltage and the spinning receiving distance.To measure the average diameter of the fiber by scanning electron microscope and Image-Pro Plus software.The nanofibrous with nanofibrous diameters of 300±20 nm,350±20 nm,400±20 nm,450±20 nm and 500±20 nm were obtained by adjusting the polyurethane solubility,spinning voltage and spinning distance.Through using gas permeation pore size analyzer,infiltration and weighing method,optical contact angle measuring instrμment,fabric moisture permeability and air permeability tester,effect of the diameter of polyurethane nanofibrous on the water vapor permeability is investigated.The results showed that the change of fiber diameter significantly influences the pore size and pore structure of nanofibrous membrane.The pore size of the membrane decreased with the decrease of the fiber diameter,and the porosity increased with the diameter of the fiber.When diameter was 300±20 nm,the pore size and porosity were 0.7014 μm and 68.23%,respectively;The water contact angle,daily moisture permeability and air permeability of the nanofibrous membrane increased with increase of the diameter of the fiber.When the fiber diameter was 300±20 nm,the contact angle,moisture permeability and air permeability were 124.75 °,5773 g / m~2 · 24 h and 14.49 mm / s,and the static water contact angle is still greater than 90° for 60 min.The water repellency and the moisture permeability of the obtained nanofibrous membrane are better.The thickness of nanofibrous has certain effects on the waterproof performance of nanofibrous membrane,by controlling the spinning fluid quantity to adjust the thickness of nanofibrous membrane(20±5 μm,30±5 μm,40±5 μm,50±5 μm and 60±5 μm).The influence of the thickness of polyurethane nanofibrous membrane on the water vapor permeability was studied by means of scanning electron microscope,gas permeation method,wetting method,optical contact angle meter,fabric moisture permeability tester and air permeability tester.The results show that the thickness of the nanofibrous membrane has a certain influence on the pore size and pore structure of the nanofibrous membrane.The pore size decreases with the increase of the thickness of the nanofibrous membrane,and the porosity increases with the increase of the membrane thickness.When the thickness of fiber is 60±5 μm,the average pore diameter of nanofibrous membrane is the smallest,which is 0.6436 μm.The porosity of nanofibrous membrane is 71.03%.The water contact angle of polyurethane nanofibrous membrane is not related to the thickness of nanofibrous membrane,and the maximμm static water contact angle is only 1.15 °more than the minimμm static water contact angle.The moisture permeation and permeability of the polyurethane nanofibrous membrane decreased with the increase of the fiber thickness.When the fiber diameter was 300±20 nm and the fiber thickness was 60±5 μm,the moisture permeability and permeability were 5179 g / m~2 · 24 h and 13.27 mm/s,greater than the general standard of the moisture permeability and significantly improve the wind performance of nanofibrous membrane.