Preparation And Performance Study Of Wet-laid Nonwovens For Separation Membrane Supports

With the rapid development of membrane separation technology and the expansion of separation membrane market,separation membrane has been widely used in seawater desalination,wastewater treatment,biological medicine,petrochemical,food and beverage processing and other fields.As the base layer of the separation membranes,the membrane support provides strong support for the separation membrane and affects the structure and performance of the separation membrane.In this paper,two kinds of high-performance separation membrane support were developed by wet-laid and hot-pressing technology.The main content are as follows:(1)Usually low-melting-point polyester(PET)fibers or other low-melting-point substance are used as binder for separation membrane supports,which is convenient to process.However,they are easy to produce thermal deformation in the drying process or high temperature application environment,thus affecting the use effect of the whole separation membrane.Aiming to the solve problems,a homogeneous composite nonwoven support(HCNS)was developed by wet-laid and hot-pressing technology using undrawn PET(UDPET)fibers as bonding fibers innovatively.The significance of hot-pressing parameters on the performances of the HCNS were systematically investigated,and quadratic regression models were established.The results show that the HCNS exhibited a smooth surface(roughness of 118 nm)and a porous structure(porosity of 21.06%and pore size of 6.548?m)with a mechanical property(tensile index of 45.80N·m·g^-1)and good film-forming performance.The ultrafiltration(UF)membranes supported by the HCNS were prepared from poly(phthalazine ether sulfone ketone),which demonstrated high permeance,high rejection rate,and long-term stability at raised operation temperature,thereby suggesting the potential application of HCNS in high-temperature filtration.(2)To further improve the surface smoothness of the separation membrane support,improve its hydrophilicity and pore structure,and reduce the thickness of the support to promote the processing efficiency of the filter cartridge,ultrafine PET fiber layer was introduced to develop an ultra-thin hydrophilic asymmetric nonwoven support with a strength support layer and an ultra-thin smooth layer.Results show that the addition of ultrafine PET fiber can improve the strength(maximum tensile strength of59.85N/15mm),smoothness(minimum roughness of 3.96nm),hydrophilicity and pore structure(minimum pore size of 1.043?m,maximum porosity of 27.02%)of the support.Under the premise of meeting the conditions,the thickness of the asymmetric support is lower than that of the monolayer support.Finally,the polysulfone ultrafiltration membrane was prepared through phase conversion method on the asymmetric support.indicating that the structure of the asymmetrical support can affect the phase separation speed and regulate the forming process of the separation membrane,which can effectively improve the mechanical properties and filtration performance of the separation membrane.