Design And Preparation Of Waterproof And Breathable Fabric Based On Styrene-butadiene-styrene Block Copolymer Electrospun Membrane

Waterproof and breathable fabric is a functional fabric which integrates water resistance,moisture permeability and wind resistance.That means not only it has the ablity of preventing water droplets permeation within a certain range of water pressure,and but also allow water vapor generated by the human body transmission to achieve moisture permeability to prevent the water vapor form a layer of condensation between the fabric and the skin,that's it is known as“respirable fabric”.This kind of fabric can not only meet the wearing under some extreme environmental conditions,but also is widely used in daily life,and it is also widely used in military and medical fields.At present,there are three types of fabric for preparing protective clothing,including high density fabric,coated fabric and laminated fabric.The waterproof and breathable membrane plays a vital role as a functional layer of the laminated waterproof and breathable fabric.For example,the famous GORE-TEX fabric which uses PTFE biaxially stretched microporous membrane as the functional layer.Designing a microporous diameter waterproof and breathable membrane as a functional layer of the laminated waterproof and breathable fabric plays a vital role.It is much smaller than the diameter of water droplets?20?m?and larger than the diameter of water vapor?0.0004?m?to achieve waterproof and breathable effect.The fabric has been monopolized in the industry for its excellent performance,but the complexity of the process,the low durability of the fabric,the physiological toxicity of the raw materials,poor degradation and environmental protection have become the key factors restricting its development.Overcoming this"blockade"technology has become an urgent problem in the field of functional fabrics.Electrospinning technology is a mature technology for the preparation of micro-nano fiber membranes,and it has a good industrial prospects.Electrospun membrane has the characteristics of micro-nano pore size,high porosity,connected pore structure and high specific surface area,and the structure and performance of the membrane can be flexiblely controlled by adjustmenting the raw materials and process parameters,it is a good method to fabric waterproof and breathable membrane with high protection,comfort and environment friendliness.Styrene-butadiene-styrene block copolymers?SBS?are a class of thermoplastic elastomers with good tensile strength and low temperature properties,and it has the advantages of excellent processing performance,weak acid and alkali resistance,and easy recycling.It is mainly used in rubber products,resin modifiers,adhesives,and asphalt modifiers.Based on its excellent performance and bulk hydrophobic properties,a series of waterproof and moisture-permeable fabrics were designed and prepared by electrostatic spinning technology using SBS as the raw material.The forming process,structure and performance of SBS electrospun membrane were discussed first.By adjusting the several key electrospinning factors for example the concentration of spinning solution,the feed rate and the addition of metal Li+and so on.The morphology and surface wettability of the SBS electrospun membrane were effectively adjusted,and the SBS electrospun membrane/polyester composite fabric with good waterproof/breathable performance and mechanical properties was successfully prepared.The results show that with the increase of the SBS concentration,the fiber diameter of the SBS electrospun membrane gradually increases,the amount of the bead gradually decreases,and the size of bead gradually increases.With the increase of Li Cl concentration,the fiber diameter of SBS electrospun membrane gradually decreased.At the same time,its mechanical properties were studied.When the SBS concentration was 9 wt%and the Li Cl content was 0.004 wt%,the electrospun membrane had good mechanical properties.At this time,the SBS electrospun membrane/polyester composite fabric had good water resistance.?63.9 k Pa?,moisture permeability?4.1 kg/m²/d?and wind resistance?5.69 mm/s?.In order to improve the waterproof and breathable performance of SBS-based electrospun membranes,in this study,a hydrophobic modified micro-nano SiO₂ powder was added to the spinning solution to construct a SBS/SiO₂ electrospun membrane with a micro-convex surface with a bead structure by one step.In this paper,500 nm SiO₂ powder was used,and 3-aminopropyltriethoxysilane was subjected to hydrophobic modification under different pH conditions.The effects of modified pH and SiO₂ addition on the morphology and surface wettability of SBS/SiO₂ electrospun membranes were investigated.SBS/SiO₂ electrospun membranes/polyester composite fabrics with good waterproof and breathable performance were prepared.The results show that when the modified pH was 5.5,the micro-convex mechanism on the surface of the SBS/SiO₂ electrospun membrane's fiber were obviously,with the addition of the SiO₂ increased,the distribution of SiO₂ in the fiber of the SBS/SiO₂electrospun membrane increases,and the protrusions were made up with SiO₂ on the surface of the fiber are gradually increase.When the modified pH was 5.5 and the SiO₂ content was 2.0wt%,the SBS/SiO₂ electrospun fiber membrane/polyester composite fabric has a water pressure resistance of 66.9 k Pa and a moisture permeability of 6.50 kg/m²/d.the moisture permeability of the electrospun membrane was improvedIn order to further improve the waterproof and breathable performance of SBS-based electrospun membrane/polyester composite fabric,a two-step post-treatment process was designed in this study.A dopamine in-situ polymerization method was used to form a hydrophilic layer on the surface of SBS electrospun membrane/polyester composite fabric,at the same time,the superadhesiveness of polydopamine?PDA?was used to attach hydrophobic gas-phase nanometer SiO₂?7-40 nm?to the fiber surface wich formed superhydrophobic structure like the lotus surface.The contact angle of the SBS/PDA/SiO₂ electrospun membrane wich obtained in this study was greater than 150°,which was a superhydrophobic surface.This study also investigated the effects of dopamine concentration and SiO₂ addition with the increase of dopamine concentration,the waterproof performance of SBS/PDA/SiO₂ electrospun membrane/polyester composite fabrics shows a trend of first an increase and then a decrease,and the moisture permeability gradually decreases.With the increase of SiO₂ concentration,the waterproof performance of SBS/PDA/SiO₂ spinning membrane/polyester composite fabric gradually increased,and the moisture permeability decreased.When the dopamine concentration was 1.0 wt%and the SiO₂ addition amount was 2.0 wt%,the SBS/PDA/SiO₂spinning membrane/polyester composite fabric has excellent water resistance?96.4 k Pa?and moisture permeability?6.12 kg/m²/d?.This study also compared the effects of different morphology of nanoparticles on SBS-based spinning membrane/polyester composite fabrics waterproof and breathable performance.Comparing lamellar nano-montmorillonite?SD-1?with spherical SiO₂,the results show.The effect of laminar montmorillonite?SD-1?on SBS-based spinning membrane/polyester composite fabric was not as obvious as spherical SiO₂.The moisture permeability of SBS/PDA/SD-1 electrospun membrane/polyester composite fabric was 6.27 kg/m²/d,which was 52.9%higher than that of SBS electrospun membrane,which was obviously improved,and the hydrostatic pressure was 65.7 k Pa,and the improvement in waterproof performance was not significant.The market demand for waterproof and moisture-permeable functional fabrics is huge.Electrospinning technology is easy to operate,low in cost,and has a broad industrial prospect,more and more polymers are being developed.It is a general trend to fabric the waterproof and breathable functional fabrics through electrospinning technology.The application prospect of fabric waterproof and breathable fabrics by using electrospinning technology is very broad.