Preparation Of Novel Cyclic Phenylene Sulfide Sizing Agent And Its Effect On The Interfacial Performance Of CF/PPS Composites

Carbon fiber reinforced resin matrix composite is widely used in military and civilian fields because of its high specific strength,high specific modulus and strong designability.Compared with conventional carbon fiber reinforced resin matrix composites,carbon fiber reinforced polyphenylene sulfide(CF/PPS)composites have the advantages of high heat resistance,good corrosion resistance,high strength,high toughness and recyclability.CF/PPS composites have broad application prospects in the fields of aerospace,national defense,military industry,rail transit and other cutting-edge science and technology.However,the surface of CF is smooth and chemically inert and the PPS resin also has poor chemical activity.There are almost no effective chemical and physical interactions between CF and PPS matrix.Therefore,the weak interfacial adhesion of CF/PPS composite remarkably affects its comprehensive mechanical properties and limits its application.In order to solve the problem of poor interfacial adhesion,CF is usually treated by sizing agents.But the commercial sizing agent usually designed for thermosetting resin,which is not compatible with thermoplastic PPS.In this study,based on the principle of similar phase solubility,a novel sizing agent was prepared by ring opening polymerization of CPS oligomer at high temperature.The novel CPS sizing agent was applied to CF/PPS composite,which effectively improved the interfacial properties of the CF/PPS composite.The CPS oligomers were obtained from the industrial waste of polyphenylene sulfide(PPS)by extraction.Its molecular structure and composition were characterized by FT-IR and TOF-MS.The ring opening polymerization of CPS can take place at high temperature,and the products is macromolecular PPS(MC-PPS).Differential scanning calorimetry(DSC)was used to study the thermal ring opening polymerization behavior of CPS.Compared with untreated oligomers,the glass transition peak of the polymers after high temperature treatment appeared at 90 ?,Abstract Preparation of Novel Cyclic Phenylene Sulfide Sizing Agent and Its Effect on the Interfacial performance which confirmed that MC-PPS was formed by polymerization.The chemical composition of the products was compared by FT-IR,and the thermal stability was analyzed by TGA.The mechanism of ring opening polymerization was studied by electron paramagnetic resonance spectroscopy(EPR).The sulfur free radical was detected in the process of ring opening polymerization,which confirmed the free radical mechanism of in-situ ring opening polymerization of CPS.The extracted CPS oligomer was dissolved in anhydrous tetrahydrofuran(THF)to prepare a solvent-based CPS sizing agent with different concentration gradients,and then the CF(Toray T700,deasphalting with acetone for 48h)was sized with CPS sizing agent.After drying at 320?,the modified CF with a layer of MC-PPS film on its surface could be obtained.The physicochemical state of the surface of the modified CFs was characterized by scanning electron microscopy(SEM),FT-IR and dynamic contact angle test.The tensile strength and thermal stability of the modified CF were characterized by a single fiber testing machine and a thermogravimetric analyzer.The results showed that the novel CPS sizing agent possessed better thermal stability and increased the surface energy,wettability and tensile strength of CF.The interfacial shear strength(IFSS),interlaminar shear strength(ILSS)and thermomechanical properties(DMA)of CF/PPS composites were tested.The fracture morphology of the composite was observed by SEM,and the effect of CPS sizing agent on the interface properties of the composite was studied.The results showed that the maximum interfacial shear strength of the CPS sizing agent modified composite was 29.57 MPa,which was 28.7% higher than that of the unmodified composite;the maximum interlaminar shear strength was 31.17 Mpa,which was 71%higher than that of the unmodified composite.The enhancement mechanism of interface strength was demonstrated as follows.The MC-PPS film formed by the CPS sizing agent on the surface of the CF,which effectively improved the compatibility between the CF and the PPS resin matrix.Moreover,during the molding process of the CF/PPS composite,the MC-PPS coating on the CF surface and the PPS resin matrix undergone a hot oxygen cross-linking reaction,forming a solid interface layer,further improving the interface adhesion strength of CF/PPS composite.