Study On Mechanical Test Method Of Nanofiber Membrane Via Electrospinning

In order to study the mechanical test method of nanofiber membrane viaelectrospinning,PA6was chosen due to its good spinnability in this paper.Uniform spinningsolution was obtained by dissolving PA6into formic acid.Then PA6nanofiber membraneswere prepared by electrospinning.In this way,a series of mechanical test methods werestudyed,such as sampling method,sampling number,the choice of testing parameters and theapplication of dumbbell-shaped specimen.First of all,sampling method and sampling numberfor tensile property of membrane should be confirmed.The suitable sampling method andsampling number were obtained by comparing three sampling methods and analysing thechange rule of variable coefficient.Then the influence of test conditions on tensile propertiesof nanofiber membrane was studyed.Using universal tester to test the tensile property andanalysing the test results by orthogonal experimental method with the testing length,drawingspeed and specimen width as three factors.In order to reduce the influence of neckingphenomenon on test results,dumbbell-shaped specimen was used to modify the shape ofstandard rectangular strip in this paper.With clamping width, parallel width, clampinglength,parallel length as four factors,using orthogonal experimental method and all factors testmethod to analyse the influence degree of all factors on the results and to get the bestmodified-shape.In the end,the tensile fracture mechanism of membrane was studyed.Thechanging situation of fiber during the tensile deformation process could obtained fromstress-strain tensile curve and the changes of fiber structure before stretching and afterbreakage could be analysed by SEM and XRD tests.The conclusions are as follows:(1)Dispersion degree of testing results is becoming smaller as the sampling numbersincrease in a certain range.And once exceed a certain limit, dispersion degree will be no moreobvious.As a result,it is perfect when sampling number is8.The thickness of samples obtainedby parallel sampling method is more uniform than the other two methods,and this method isthe most reasonable for the results of tensile test.As a result, parallel sampling method is themost suitable for nanofiber membrane by electrospinning as a sampling method.(2)Within the influencing factors of tensile properties of the nanofiber membrane,thedrawing speed is the most important influencing factor and specimen width is the leastimportant for deviation coefficient of tenacity.And the testing length is the most importantinfluencing factor and specimen width is the least important for deviation coefficient ofelongation at break.The optimal test condition of the tensile properties of nanofiber membraneis that the testing length is40mm, drawing speed is5mm/min,and specimen width is8mm.(3) Within the shape factors of dumbbel-shaped specimen,the impact of parallel width onbreaking strength is the largest,while the impact of clamping width is the least.Properdumbbell-shaped specimen can reduce the irregularity markedly in the tensile test ofnanofiber membrane.The breaking position in the tensile test can be controlled in the middleof the sample by changing parallel length so that it can reduce the influence of stressconcentration on the test result.The best modified-shape for the standard rectangular strip is that clamping width is14mm-18mm,the parallel width is8mm,and the clamping length is40mm,and the parallel length is10mm.(4)PA6nanofiber membrane experiences elastic stage,yield phase,hardening stage andbreakage during the tensile deformation process.And from the stress-strain tensile curve wecan see,PA6membrane belongs to brittleness material.The diameter of fibers obtained byroller is smaller and the orientation is better than obtained by panel.After the breakage,theadjacent fibers will draw together and will get orientation along the direction to extrude.Fiberswill be tortuous.Crystalline texture of membrane does not change before stretching and afterbreakage.