Structural Regulation And Protective Properties Of PVDF Nanofibers

With more and more attentions are being paid to the damages of harmful solid particles to health,the demands for functional protective textiles are increasing in many fields of application,especially in petroleum,chemical industry,medical and other occupations that may be exposed to hazardous chemicals.Nanofibers have a good barrier function to particles,and have a good application prospect in the field of protection.In this dissertation,PVDF nanofibers were solution blown with varieties of morphology and structure to develop functional protective materials.In view of the poor mechanical properties of the nanofiber nets,the mechanical properties of PVDF nanofibers were adjusted by adding cross-linking agent(TMPTA)and photoinitiator(TPO)to the spinning solution of PVDF.The crosslinked PVDF nanofiber network was designed and prepared by solution blowing method.The results show that when TMPTA is added,the mechanical properties of the nanofiber nets can be improved obviously.Compared with the pure PVDF nanofiber nets,the tensile breaking strength and elongation at break increase 44.1%and 88.6%respectively.The filtration efficiency is 100%for particles larger than 230nm,while the filtration resistance is only 320Pa.In the meantime,the permeability can reach 32.42 L/m~2·s,and the moisture permeability can reach 211.7 g/m~2·h.As a protective material,it has a good performance of blocking particles.Aiming at the poor air permeability of nanofiber nets,the structure of PVDF nanofibers was adjusted by adding PS polymer to the spinning solution,and the bead-on-string nanofibers with good morphology were designed and prepared by using electrostatic assisted solution blowing.The results show that when the mass fraction of PVDF and PS is 7%,the bead structure and morphology of the prepared nanofibers are the best,and the mesh has good air permeability,which can reach 37.76 L/m~2·s.At the same time,the low concave surface of nano size can absorb gas molecules,which is equivalent to a stable gas film on the macro surface,with good water repellency and contact angle as high as 132.6 degrees.As a protective material,it shows good air permeability and provides comfort for operators wearing protective clothing.To endow the nanofiber nets with environmental response performance,by adding dimethyl sulfoxide(DMSO)and bromocresol purple(BCP)developer to the spinning solution of PVDF and PS,and using the electrostatic assisted solution blowing method to design and prepare the ammonia gas response porous bead-on-string nanofibers.The pore size distribution of bead-on-string nanofibers was analyzed qualitatively and quantitatively by SEM and BET.The results show that when the BCP content is 0.3%,the response range is wide and the response sensitivity is high,which can respond to the ammonia gas with 100 ppb content in the environment.It can provide a good early warning function for the workers in ammonia industry and has a potential application prospect.