| Since the carbon fiber is brittle, carbon fiber production and processing tends to undergo repeated friction and fracture process, reducing the strength of the fiber body, and producing a large number of bristles. All these are not conducive to the subsequent application. By sizing process, the carbon fiber surface is coated with a layer of polymer sizing agent to protect carbon fiber body performance, while reducing fuzz volume and improving the fiber bundle. The carbon fiber processing performance and production environment have been significantly improved. In addition, the carbon fiber surface coating sizing resin also increases the wettability of carbon fiber with matrix resin to reduce interface defects, thereby improving the bonding strength between the fibers and the resin matrix. This shows that the sizing agent plays a very important role in the carbon fiber production process.In this thesis, an epoxy resin E-44, E-51 and a bisphenol F type epoxy resin body BPF as sizing, plus a variety of emulsifiers, were used to prepare for a class of extra-emulsifying epoxy sizing agent (EX-SA). Secondly, diethanolamine (DEA) and p-amino benzoic acid (PABA), respectively, was used to modify epoxy resin E-44. DEA modified E-44 and PABA modified E-44 were synthesized, and the self-emulsifying method was used successfully to prepare cationic sizing agent (CA-SA) and anionic sizing agent (AN-SA). Finally, epoxy resin E-51 was modified by polyethylene glycol (PEG). PEG-modified epoxy resin E-51 was synthesized and the self-emulsifying sizing agent (a nonionic (NO-SA)) was prepared. The optimum preparation process of the above four categories epoxy resin emulsion was discussed. The commercially available Japanese sizing agent (JP-SA) and homemade four types of epoxy emulsion sizing agent were used for carbon fiber sizing treatment. The carbon fiber sizing rate, gross amount of wire, surface morphology and properties of sizing carbon fibers, and the mechanical properties of sizing carbon fiber monofilament were evaluated. In addition, the mechanical properties of polyamide composites reinforced by sizing carbon fiber were studied.The main results are as follows:1. The optimal conditions for EX-SA are the ionic emulsifier sodium dodecyl sulfate (SDS) with 2%, nonionic emulsifiers of polyoxyethylene sorbitan monooleate (T-80) with 2%, nonionic emulsifiers alkylphenol ether (OP-10) with 4%, emulsifying temperature at 80℃, emulsifying time for 30min, add water rate of 3 mL/min. The optimal conditions for CA-SA are E-44 and DEA molar ratio of 1:1.1, reaction temperature at 70 ℃, reaction time for 60min, ice acetic acid salt-forming temperature of ℃, water temperature of 80℃, water rate of 5 mL/min. The optimal conditions for AN-SA are PABA and E-44 molar ratio of 1:1, reaction temperature at 80℃, reaction time for 2 h, triethanolamine (TEA) and PABA molar ratio of 1:0.8, salt-forming temperature at 65℃, water temperature at 60℃. The optimal conditions for NO-SA are E-51 and PEG 1000 molar ratio of 1:1, catalyst triphenylphosphine (TPP) with 0.5%, reaction temperature at 180℃, reaction time for 3h, water temperature at 80℃.2. EX-SA and JP-SA treated carbon fibers show slightly higher sizing rate than the self-emulsifying sizing agent (CA-SA, AN-SA, NO-SA). After sizing treatment of carbon fiber, the amount of fiber bristles shows substantial reduction. Carbon fiber surface shows obvious uneven trenches and after sizing shallow trench fiber surface is obtained. After sizing treatment of carbon fiber surface, O element content is substantialy increased. In addition, CA-SA and AN-SA treated carbon fibers also contain small amount of N element. The weight of carbon fiber sizing agent decreases within the range of 300-450℃ after sizing. The tensile strength of carbon fiber monofilament before and after sizing does not change much.3. The density of the carbon fiber composite material increases with the amount of carbon fiber. The flow index of carbon fiber composite material decreases with increasing carbon fiber content. The tensile strength and flexural strength of carbon fiber composite material increases with increasing carbon fiber content. Compared with the untreated carbon fiber, the tensile strength and flexural strength of the sizing carbon fiber are increased. The Izod notched impact strength of the untreated carbon fiber composites decreases with increasing carbon fiber content, while the Izod notched impact strength increases first and then decreases for the composites with increasing carbon fiber, which after sizing. The carbon fiber and matrix resin joint surface is smooth in the cross section of unsized carbon fiber prepared composite, while the resin matrix and carbon fibers are linked closely in the cross-section of sizing carbon fibers reinforced composites. The surface between the matrix resin and sizing carbon fibers is rough. With the increase of carbon content, the storage modulus of composites increases, while the loss tangent is reduced and shifted to higher temperature. |
