Study On Properties Of Combination Of Woven Or Knitted Fabrics And Nonwovens

With the development of modern scientific technology, the levels of industries have beenincreased and so do people’s awareness of environmental protection.As a result, the need forfiltration materials in the world goes up rapidly.Nowadays, woven and nonwoven filtrationmaterials have a wide application in medicine and manufacture.An increasing number ofresearchers at home and abroad have studied the combination of woven or knitted fabrics andnonwovens.However,the relation between surface or section structure and properties has notstudied deeply.Therefore,their making efforts to do this has good effects on academy andapplication value.The main subjects in this paper are composite filtration materials of woven or knitted fabricsand needle-punching nonwoven fabrics.The structures and properties were measured andanalyzed through PSM-165, SX-L1050, scanning electron microscope,YG461D. The surface andsection structures, pore characteristic,mechnical properties,filtration efficiency and filtrationresistance were focused.Furthermore,the influence of compound technology on structures and properties were alsostudied.The conclusions that can be drawn are as follows.（1）After needle-punching, thickness and surface density of composite fabrics are increased.Porosity is reduced in a small scale and stays about89%.There is a wider pore size distributionthan original needle-punched nonwovens,namely4-40.The biggest pore size ranges from35to40and it is smaller than that of nonwovens.The tensile strengths of composite fabrics are above200N and they can meet the need in usual application.The filtration efficiency rises up while thefiltration resistace goes down.Generally,The horizontal strength is much larger than verticalstrength and the difference between them is very obvious.（2）The difference of spunlaced composite fabricsA、B、C、E、G in air permeability is notapparent.It all reaches approximately1500mm/s,so they have a good air permeability. However,air permeability of spunlaced composite fabrics D,F is a little lower and they all arrive at about 1000mm/s.Compared with spunlace nonwovens,the air permeability of spunlaced compositefabrics goes down and average pore size is also reduced.But the extent is not large and it rangesfrom0.4μm to6.35μm.It can been seen from the figure that the maximum pore size rises but theextent is also small and stays below9μm.Both filtration efficiency and resistance of spunlacedcomposite fabrics go up.The horizontal strength of A,B,G is a little larger than that of spunlacednonwovens while the vertical strength is a little smaller or equal to that spunlaced nonwovens.Atthe same time,the difference between horizontal strength and vertical strength of compositefabrics goes down obviously.The horizontal strength of C,D,E,F is larger than single-layerednonwovens but the vertical strength is smaller.（3）M values of needle-punched composite fabrics which is Ratio of longitudinal strengthand horizontal strength are mainly between0.5and1and the anisotropy is notapparent.However,the M values of spunlaced composite fabrics are all above1and theanisotropy is much apparent.For needle-punched and spunlaced composite fabrics, airpermeability,filtration efficiency in unit surface density are reduced with the increase ofthickness while air permeability and filtration resistance in unit thickness are dropped with theincrease of surface density.Needling density has a big influence on filtration performance of composite fabrics.With theincrease of needling density,the surface density,thickness,air permeability,porosity are reduced atfirst and then increased;filtration efficiency changes little and then drops;the pressure drop goesup firstly then down.When compound technology is explored,it is found that300s/cm2is thebest parameter and the composite fabric under this has better filtration performance.