Preparation Of ZIF-8@SCFs Reinforcement And Study On Epoxy Resin Composites

Carbon fiber/epoxy resin composites(CFRP)have been applied in aerospace and other front-end fields for reducing costs and lightening the structure weight,owing to their high specific strength,large specific modulus,light weight,designability and corrosion resistance.However,some issues still exist in the practical engineering application for the CFRP,such as weak interface bonding between fibers and martix,the brittle fracture,and so on.Therefore,in order to improve the mechanical properties of CFRP under a variety of loadings and the adaptability in various working environments,it is necessary that the simple,economical and effective methods should be used in modification of the carbon fibers surfaces and toughening of the resin matrix.Firstly,the nano metal-organic framework particles(ZIF-8)were grafted onto the surface of short carbon fibers(SCFs)by a facile in-situ growth method to prepare a multi-scale reinforcement ZIF-8@SCFs.The morphology,crystal structure and chemical element composition of ZIF-8@SCFs were investigated,and the results showed that the introuding of nano ZIF-8 significantly increased surface roughness and number of functional groups of SCFs,thereby enhancd the mechanical anchoring and chemical bonding between the SCFs and resin matrix.Then,composites were prepared with ZIF-8@SCFs as the reinforcement and epoxy resin(E-51)as the resin matrix.The curing kinetics of the composite system,the mechanical and thermomechanical properties of the composite were studied.The results showed that the nano-ZIF-8 grafted onto the surface of SCFs can promote the curing reaction of epoxy system.When the content of ZIF-8@SCFs was 1 wt%,the tensile strength,flexural strength,elastic modulus,toughness and impact strength of the composites were respectively increased by 25%,31%,51%,28%,and 42%compared with unmodified SCFs composites.The storage modulus of composites was increased to 3000 MPa,and the glass transition temperature was increased to 147.6 ~oC,which had a better high temperature adaptability.Aromatic polyether-type hyperbranched epoxy resin(HPE)was prepared by proton transfer polymerization,and it was used as a toughening agent for the E-51 matrix.Then,the three component composites were prepared with the addition of HPE,ZIF-8@SCFs and E-51.The thermal stability,mechanical properties and thermomechanical properties of the composites were studied,and the experimental results were analyzed in combination with their respective toughening mechanisms.The results showed that HPE can toughen the composites without affecting its mechanical strength and thermal stability.In addition,HPE can not only promote the curing reaction of E-51,but also further improved the interface bonding strength between ZIF-8@SCFs and E-51,therefore it can significantly improve the mechanical and thermomechanical properties of the composite.When the contents of HPE and ZIF-8@SCFs were 8 wt%and 2 wt%,respectively,the tensile strength,flexural strength and the impact strength of the composite were 83.85 MPa,185.61 MPa and 9.98 k J/m~2,respectively.The glass transition temperature have been increased to 171 ~oC.At the same time,the excellent thermal stability of the matrix was maintained.