Study Of Polysulfone Nanofibrous Membranes Toughened Epoxy Resin And Carbon Fiber Composite

Toughening methods of carbon fiber/epoxy composite are the important target of advanced composite development.In the second generation composite,thermoplastics have been used to toughen epoxy matrix by physical blending.However,composite fibrication was difficult due to the high viscosity of blending systems.In the third generation composite, thermoplastic particles or films prepared by solvent method have been used in the interlaminar toughening composite.However,among these methods some limitations still existed in practical utility,such as the low fluidity of polysulfone(PSF) and permeability of resin matrix etc.Therefore,we suggested a novel method to toughen the composites using electrospun PSF nanofibrous membranes.Unique properties of nanofibrous membranes, such as small diameter,large porosity and high specific surface area, allowed the nanofibers being easily impregnated by epoxy matrix to increase the compatibility,resulting in easy dissolution into matrix.1.Polysulfone nanofibrous membranes were prepared by electrospinning of PSF solutions in mixtures of N,N'-dimethylacetamide(DMAC) and acetone.Increasing the acetone amount and the polymer concentration was beneficial to produce electrospun nanofibrous membranes with uniform morphology.Raising the applied voltage tented to produce smaller diameters of the electrospun nanofibers,while applying a lower flow rate was favorable to avoid bead-fiber morphology.2.A novel approach for toughening carbon fiber/epoxy composite using electrospun PSF nanofibrous membranes was performed.As-received membranes were composed of nanofibers with random orientation,and were directly electrospun onto layers of carbon fiber/epoxy prepregs to toughen the composites.According to the random dispersed nanofibers on the membranes,the inhomogeneous phase separation of polysulfone,which was generated in-situ along the nanofibers direction during the curing of epoxy matrix,was proposed.PSF spheres exhibited random alignment in "sea-island" morphology and presented uniform dispersion through the composite interlayers.Mode I and II inteflaminar fracture toughness(G_â… C & G_â…¡C) of 5 wt%PSF nanofibrous membranes toughened composite increased by 181%and 177%,which were higher than those of 5 wt%PSF films toughened composite.DMTA tests revealed good compatibility between nanofibrous membranes and epoxy matrix.3.The isothermal curing kinetics of epoxy matrix,5 wt%PSF nanofibrous membranes and films toughened epoxy resins were investigated by Differential Scanning Caliorimetry(DSC) and Near Infra-red Spectroscopy(NIR).The fundamental kinetic parameters were compared,and the conversion of epoxide group and the curing rate exhibited identical variations.At the initial curing stage,the curing rate of PSF nanofibrous membranes toughened epoxy resin was faster than that of PSF films toughened epoxy resin and epoxy matrix,whereas the final conversion degree of PSF nanofibrous membranes and films toughened epoxy resins was lower than that of epoxy matrix.The curing mechanism could be explained by the variation of primary amine from NIR testing.4.Electrospun nanofibrous membranes of PSF/CNTs hybrid were prepared by using CNTs treated with the mixture of H₂SO₄ and HNO₃.The tensile,impact and thermal properties of nanofibrous membranes toughened and reinforced epoxy matrixes were investigated.When the content of nanofibrous membranes was 3 wt%,the tensile strength and impact strength of toughened and reinforced epoxy matrixes were increased by 12%and 10%,respectively,and the glass transition temperature(T_g) was enhanced by 4℃.The synergism effects of toughening and reinforcing were due to PSF spheres from the inhomogeneous phase separation and CNTs at different sites in epoxy matrix or PSF spheres.