Preparation And Properties Of Porous Poly(Lactic Acid) Nanofibers

Based on the electrostatic spinning preparation of porous polylactic acid nanofiber membrane,and respectively by acetone immersion and gas foaming expansion of fiber membrane for two kinds of different forms of post-processing,by scanning electron microscope(SEM),Fourier transforms infrared spectroscopy(FT-IR),aperture tester and automatic analysis of characterization,such as specific surface area analyzer and the processing of the samples before and after oil absorption performance tests,specific as follows:(1)PLLA nanofiber membrane was prepared by electrospinning method,and the effects of PLLA solution concentration,a volume ratio of benign solvent DCM and non-benign solvent DMF,electric field intensity,voltage,and receiving distance on fiber morphology and diameter distribution were explored.The experimental results show that 17% of the spinning solution is the best concentration.Under this concentration,the porous fibers with larger surface holes,more dense distribution,and more uniform diameter can be prepared by electrospinning.When the ratio of two solvents to DCM/DMF is 8:2,the pores on the prepared porous fibers are denser and deeper than those of other solvents,which is an ideal fiber morphology.When the electric field intensity(spinning voltage: receiving distance)is1.0,the porous fibers with large pore size and dense pore size distribution can be prepared.When the spinning voltage is 16 k V and the receiving distance is 16 cm,the fibers are uniformly distributed with dense pores,which are the optimal parameters of voltage and receiving distance.(2)PLLA nanofiber membrane was prepared by electrospinning,and then the prepared fiber membrane was immersed in acetone solution for different time post-treatment.The surface morphology,infrared spectrum,mechanical properties,pore diameter and BET,wettability,and oil absorption properties of the membrane before and after acetone treatment were tested and analyzed,and the effects of acetone treatment and its treatment duration on the properties of the membrane were discussed.The following conclusions are drawn: the pore structure of the fiber surface can be increased by acetone treatment;Acetone treatment did not affect the functional groups of PLLA.With the increase of acetone treatment time,the mechanical properties of the fiber membrane become worse and worse.After acetone treatment,the average pore size of the membrane becomes smaller and the pore size distribution becomes more and more concentrated.After acetone treatment,the specific surface area of the fiber membrane increased significantly,and the pore area of the single fiber increased significantly.After treated with acetone,the water contact Angle of the fiber membrane ranges from 130 ° to 150 °.Poly(lactic acid)porous nanofiber membrane itself has a good oil absorption performance.The oil absorption ratio of the fiber membrane can be increased by at least one time if the acetone is treated for a suitable time.The performance of the fiber membrane can reach the best state after treatment for 5 min.(3)PLLA nanofiber membrane with surfactant F-127 was prepared by electrospinning,and then the prepared fiber membrane was expanded with different concentrations of ammonium bicarbonate aqueous solution.The surface morphology,infrared spectrum,mechanical properties,pore size,and oil absorption properties of the expanded nanofiber sponge were tested and analyzed.The effects of different concentrations of F-127 and the concentration of ammonium bicarbonate on the properties of the sponge were discussed.The results show that the polylactic acid nanofiber membrane can be successfully expanded into a 3D nanofiber sponge by gas foaming technology.After expansion treatment,the inner fibers of the membrane form a multi-layer structure and the outer fibers of the membrane change from a two-dimensional membrane to a 3D spongy shape.When the concentration of F-127 is0.6% and the concentration of ammonium bicarbonate solution used for expansion is 10%,the nanofiber sponge obtained after the expansion is the thickest,and the thicker film has better oil absorption performance.It was found that the addition or dissolution of the active agent F-127 did not affect the functional groups of PLLA.When the content of F-127 in the fiber membrane is 0.2% and the concentration of ammonium bicarbonate for expansion is10%,the mechanical properties of the expanded sample are the best.Although the pore sizes of the expanded nanofiber sponges are slightly different under different conditions,they are generally more concentrated.When the concentration of expansion of ammonium bicarbonate was 10%,the content of the F-127 in fiber membrane was 0.6% after inflation of the sample oil absorption effect is best,silicone oil,soybean oil,and engine oil absorption ratio reached 101.73 g/g respectively,83.58 g/g and 45.21 g/g,expansion treatment after nanofibers sponge with three different densities of oil effect is good,have reached more than 80%.