Melt Electrospinning Controls The Morphology Of PLA Fibers And Prepares Fe₃O₄/PCL Composite Micro-nano Fibers

Recently,electrospinning has made a rapid progress in the preparation of nanomaterials,with good progress in the fields of principle,application,materials and devices.Electrospinning can be divided into solution electrospinning and melt electrospinning depending on whether solvent required in the electrospinning process.Compared with the former,the latter has the advantages of no environmental pollution caused by toxic solvents and high material conversion rate.Melt electrospinning has received extensive attention in the industrial field.Micro-nanofibers with different morphological structures and inorganic/organic composite polymer fibers doped with different materials could be prepared by solution electrospinning,There are few reports in preparation of inorganic/organic composite polymer fibers via melt electrospinning.In this paper,the control of fiber morphology and the preparation of inorganic/organic composite fibers by melt electrospinning technology have been studied.Here,we report that the morphologies of polylactic acid（PLA）via melt electrospinning also can be adjusted from microfibers to microspheres by simply increasing the spinning temperature.It was found that with temperature increasing from200°C to 240°C,the average diameter of melt-electrospun PLA fibers decreased from58.46 to 2.96μm.Then,beaded fibers and microspheres about 14.5μm in diameter were collected when the spinning temperature was increased to 250°C and 260°C.In addition,we also found that the average diameter of PLA fiber decreased with increasing the applied spinning voltage,and increased with the increase of spinning distance.To explain the formation mechanism of different PLA microstructures,rheological property and infrared spectra of PLA under different spinning temperatures were also tested.The rheological properties,infrared spectroscopy and thermogravimetric tests of PLA fibers obtained at different spinning temperatures were carried out.It was found that the changes of PLA fiber morphology are related with sharply decreasing in molecular weight caused by transesterification with high temperature.Secondly,we prepared Fe₃O₄/PCL composite micro-nanofibers by melt electrospinning.The effects of experimental parameters（voltage,received distance,spinning temperature and Fe₃O₄ content）on the morphology of Fe₃O₄/PCL composite micro/nanofibers were studied.The increase in the content of Fe₃O₄ nanoparticles will increase the degree of polymerization of Fe₃O₄ particles,causing the particles to be exposed on the surface of the fibers,and the maximum particle size exceed 1μm.In order to study the influence of the presence of Fe₃O₄ nanoparticles and PCL,XRD,IR and DSC were tested on Fe₃O₄/PCL composite micro/nanofibers.The test results show that there is only physical compounding between Fe₃O₄ and PCL.Finally,the magnetic properties of Fe₃O₄/PCL composite micro/nanofibers were tested.The experimental data show that:the increase of magnetic nano-particle content does not significantly affect Fe₃O₄/PCL composite micro-nano fiber.Saturation magnetization increases with the increase of Fe₃O₄ nano-particle content,and the saturation magnetization can reaches 38.0 emu/g.The thermal effect of Fe₃O₄/PCL composite micro/nanofiber membrane in alternating magnetic field was studied.It was found that the magnetic field strength had the greatest influence on the heating of Fe₃O₄/PCL composite micro/nanofiber membrane,and the highest equilibrium temperature could be 43.8 ^oC.The mass of composite micro-nanofiber membrane and the Fe₃O₄ content in the composite fiber membrane also have an effect on the heating process of the composite fiber membrane.