A substrate for a liquid filter, which includes a polyolefin microporous membrane, the polyolefin microporous membrane having a water permeation efficiency of 0.10 to 0.50 ml/min.Math.cm.sup.2, the polyolefin microporous membrane having a bubble point of 0.50 MPa or more and 0.80 MPa or less.

A substrate for a liquid filter, which includes a polyolefin microporous membrane, the polyolefin microporous membrane having a water permeation efficiency of 0.51 to 1.20 ml/min.Math.cm.sup.2, the polyolefin microporous membrane having a bubble point of 0.45 MPa or more and 0.70 MPa or less, the polyolefin microporous membrane having a compressibility of less than 15%.

A substrate for a liquid filter, which includes a polyolefin microporous membrane, the polyolefin microporous membrane having a water permeation efficiency of 1.21 to 2.90 ml/min.Math.cm.sup.2, the polyolefin microporous membrane having a bubble point of 0.40 MPa to 0.65 MPa, the polyolefin microporous membrane having a compressibility of less than 15%.

The present innovation relates to novel and versatile nanomembrane to be used in filtration system and manufacturing method to produce it. The filter membrane may result in significant reduction in energy demand and higher capture efficiency. The filter membrane may have one or multiple nanomembrane part of overall filtration system. The manufacturing uses a combined electric and air flow field to produce the nanomembrane, which may be included as in-line module in standard filter manufacturing process. The method of nanomembrane production is optimized by machine learning-based optimization protocol based on physics-based modeling via feedback control.

The present invention provides a porous membrane for water treatment, comprising: a high molecular weight polyethylene, a water-soluble polymer and an antioxidant, the high molecular weight polyethylene having an average molecular weight of 1.0×10.sup.5 to 10.0×10.sup.6 and a density of 0.940 to 0.976 g/cm.sup.3; wherein, the weight of the water-soluble polymer is 5 to 50 parts, the weight of the antioxidant is 0.1 to 10 parts, based on 100 parts of the weight of the high molecular weight polyethylene. The porous membrane for water treatment prepared by the present invention has a thickness of 5 to 30 μm, a pore size of 10 to 100 nm, a porosity of 20 to 60%, and a surface contact angle of 30° to 95°. The porous membrane according to the present invention has good durability, simple preparation process, and relatively thin thickness, a uniform pore size distribution and small pore size, good hydrophilicity, as well as good filtration and adsorption effect.

The disclosure provides a method for preparing a hollow fiber membrane by melt spinning-stretching and selective swelling, including: preparing a nascent hollow fiber by melt spinning in an inert gas protective atmosphere by using an amphiphilic block copolymer as a film forming material, and stretching the nascent hollow fiber in the cooling process, a stretch rate being controlled at 200-540 mm/min, and a stretch ratio being controlled at 150-600%; immersing the obtained hollow fiber in a swelling solvent, and treating the hollow fiber in a water bath at 65° C. for 1 h; and then transferring the hollow fiber into a long-chain alkane solvent, treating the hollow fiber at the same temperature for 1-12 h, and after the completion of the treatment, immediately taking out the hollow fiber and drying the hollow fiber to obtain the hollow fiber membrane with a bicontinuous porous structure. By combining the melt spinning-stretching and the selective swelling, the method of the disclosure can synchronously and continuously improve the permeability and selectivity of the hollow fiber membrane. The treatment in the long-chain alkane solvent can make the polar chain excessively enriched on the surface of the membrane migrate inward, thereby improving the performance of the hollow fiber membrane.

A microporous membrane has average membrane thickness of 15 μm or less, and relative impedance A after a heat compression treatment under a pressure of 4.0 MPa at 80° C. for 10 minutes of 140% or less, the relative impedance A being obtained by the equation below: Relative impedance A=(impedance measured at 80° C. after the heat compression treatment)/(impedance measured at room temperature prior to the heat compression treatment)×100.

A method of forming an unsintered biaxially expanded PTFE/thermoplastic polymer composite membrane is provided. The method includes blending fibrillatable polytetrafluoroethylene (PTFE) particles and thermoplastic polymer particles where the melting point of the thermoplastic polymer particles is less than the melting point of the fibrillatable PTFE particles. The method further includes forming the blend into a tape and expanding and heating the tape in a first direction at a first temperature. The expanded tape is then expanded, either concurrently or sequentially in a second direction to form an ePTFE composite membrane. The method does not include a sintering temperature. The ePTFE particles and thermoplastic polymer particles have an average particle size of less than 1 μm. In addition, the ePTFE composite membrane has a geometric mean matrix modulus to geometric mean matrix tensile strength ratio of at least about 6 and an absolute dimensional change percentage of less than about 1.5%.

A method for producing a microporous material comprising the steps of: providing an ultrahigh molecular weight polyethylene (UHMWPE); providing a filler; providing a processing plasticizer; adding the filler to the UHMWPE in a mixture being in the range of from about 1:9 to about 15:1 filler to UHMWPE by weight; adding the processing plasticizer to the mixture; extruding the mixture to form a sheet from the mixture; calendering the sheet; extracting the processing plasticizer from the sheet to produce a matrix comprising UHMWPE and the filler distributed throughout the matrix; stretching the microporous material in at least one direction to a stretch ratio of at least about 1.5 to produce a stretched microporous matrix; and subsequently calendering the stretched microporous matrix to produce a microporous material which exhibits improved physical and dimensional stability properties over the stretched microporous matrix.

A method for making a filter membrane includes: forming a polymer layer; applying a plurality of nanoparticles on the polymer layer, the nanoparticles being self-assembled to form a closed pack arrangement on the polymer layer; heating the nanoparticles such that a portion of the polymer layer contacting the nanoparticles is softened so that the nanoparticles are sunk into the polymer layer; and removing the nanoparticles from the polymer layer so that the polymer layer is formed with a plurality of pores penetrating the polymer layer and being arranged in a honeycomb pattern.