Fabraction Of Polyvinylidene Fluoride/Poly (Vinyl Butyral) Composite Nanofibrous Membranes For Waterproof-breathable Application

Be identified as the “second skin” of people,waterproof-breathable fabric prevents the penetration of water while allowing moisture vapor transforming from wearers that can provide effective comfort and protection for human beings.Waterproof and breathable membranes as the core functional layer of the breathable barrier fabrics has been widely used.However,many waterproof moisture-permeable films on the market have complicated manufacturing processes,high cost and generation of persistent solid pollutants,even though they have a good water-resistant but very hot to wear,or wearing comfortably but easy to wet when suffered from rain and snow.Therefore,it's urgently to develop a waterproof and breathable film that can make up for these shortcomings.According to the research,water resistance of the membranes increases with the decrease of pore size,and the moisture permeability increases with the increase of porosity.While the nanofiber membrane prepared by electrospinning has the advantages of fine fiber diameter,optimized pore size and porosity,which can be used to prepare waterproof-breathable nanofibrous membranes.Duo to polyvinylidene fluoride(PVdF)has hydrophobicity,thermal stability and other characteristics that can increase the material's water resistance and heat resistance,polyvinyl butyral(PVB)has a low melting point which can increase the fiber adhesion structure and decrease the maximum pore diameter(dmax)that improve the mechanical property of the membranes.Therefore,using PVdF and PVB as raw materials,and N,N-dimethylacetamide(DMAc)as solvent,PVdF/PVB composite waterproof and breathable nanofibrous membranes was fabricated through electrospinning followed by heat treatment.And their morphology,mechanical properties and waterproof-moisture permeability were studied.The goal is to obtain waterproof-breathable membranes with excellent comprehensive performance.In this study,the fiber morphology,mechanical properties and water vapor permeability of electrospun fiber membranes were investigated to use different concentrations of 8 wt%,10 wt%,12 wt%,14 wt% by weight of the mixed polymer.The results show that when the polymer concentration is lower than 10wt%,the solution viscosity is weaker and there are more beads and some fibers break,so the breaking strength and elongation are lower.When the concentration is higher than 10wt%,the fiber diameter subjoined,the fiber membrane permeability increased,but the tensile strength and water pressure decreased.Based on the porous structure and comprehensive performance,10 wt% was the best polymer concentration.Then,studying the effect of relative humidity(55%,65%,75%)on the morphology and properties of the fiber,the relative humidity of 65% was selected,because that the fibrous membranes has optimum mechanical properties.In order to research the influence of the roles of two polymers on the structure and property,the mass ratio(w/w)of PVdF to PVB was adjusted to 10/0,9/1,8/2,7/3,6/4,5/5.The results revealed that the higher the PVB content,the lower the fluorine content in the solution,the fibers become more adhered after heating.The tensile strength of the fiber membrane increases and the hydrostatic pressure decreases,the results show that the optimal ratio of PVdF to PVB is 8/2.Since the melting point of PVB is very low,the adhesion between fibers will be increased after heat melting.Therefore,the heating temperature was choosing as 120,140 and 160? for 30 min.The experimental results show that at the heat treatment temperature(140?),the composite membranes are endowed with robust tensile stress of 10.5 MPa and good breaking elongation of 64.5%,which are about four times that of the pure non-bonded PVdF membranes.Apart from these,the bonded PVdF/PVB membranes express integrated properties of high water vapor transmittance rate(10.6 kg/m~2/d),modest air permeability(9.8 mm/s),and good waterproofness(58 kPa)Therefore,the good comprehensive performance of the as-prepared membranes suggested their potential applications in tents,protective clothing,surgical clothing,building facades,aerospace and so on.