Preparation And Properties Of PVDF Piezoelectric Yarn And Flexible Wearable Fabric

In recent years,with the rapid development of the intelligent wearable devices,intelligent wearable textiles formed by combining with textiles have been widely used in monitoring various physiological or pathological signals of the human body.At the same time,higher requirements have been put forward for flexible energy conversion devices and whether they can satisfy the wearers comfort and durability.Polyvinylidene fluoride(PVDF)as a kind of semi crystalline piezoelectric polymer,which can convert mechanical energy into electricity and compared with other traditional piezoelectric material is qualitative light,soft,wide frequency response range,high sensitivity,the advantages of easy processing and so on.Meanwhile,as one of the excellent power supply materials in intelligent wearable textiles,it has attracted extensive attention.In this paper,different concentrations(8%,10%,12%)of PVDF nanofiber membranes were prepared by electrospinning method.The influence of concentration on the morphology of PVDF nanofiber membranes was analyzed by SEM.After the optimal spinning concentration was obtained,the effects of spinning voltage on the fiber diameter,crystallinity and piezoelectric properties of PVDF nanofiber films were investigated by changing spinning voltage.Then,PVDF piezoelectric yarn was prepared by electrospinning and 2D braided,the morphologies,piezoelectric properties,mechanical properties and durability of piezoelectric yarns were studied,respectively.And the piezoelectric yarn is woven into a soft intelligent piezoelectric fabric with plain texture structure.At the same time,the morphology and piezoelectric properties of piezoelectric fabric,comfort and durability were studied.In addition,the electrical signal response of piezoelectric yarn and piezoelectric fabric under different motion states of human body is investigated in this paper.The main conclusions are as follows:(1)When the spinning concentration is 10% and the spinning voltage is 15 k V,the fiber diameter distribution of PVDF nanofiber membrane is uniform,and the piezoelectric output value is the highest,which can reach 0.93 V.(2)The piezoelectric yarns with uniform morphology,excellent piezoelectric properties,strong durability and excellent mechanical properties can be prepared by the combination of electrospinning and 2 D braided.The maximum output voltage and current of the piezoelectric yarn are 120 m V and 17.3 n A respectively.After 30 minutes of water washing test,the output voltage remained basically unchanged.The test results of mechanical properties show that the maximum stress of piezoelectric yarn is 87.4 MPa and the maximum strain is 78.9%.After3200 cycles of piezoelectric yarn stability test,the output voltage is basically unchanged.(3)Compared with piezoelectric yarn,piezoelectric fabric has a greater improvement in electrical signal output.Compared with common fabrics,piezoelectric fabric can satisfy the standard of human body wearing in terms of durability and comfort.The maximum output voltage of the fabric is 0.59 V,the maximum output current is 32.8 n A,which can charge the voltage of the capacitor of 2.2 ?F to 0.6 V in 60 s.The piezoelectric fabric has a permeability of 349.7 mm/s,a static suspension coefficient of 72.25% and a maximum bursting strength of980.22 N.(4)Piezoelectric yarn/piezoelectric fabric can detect the changes of electrical signals under different motion conditions of the human body,which lays a foundation for the further development of wearable.