| As a continuous phase of composite materials, the matrix resin plays a decisive role in the comprehensive performance of the composite material. Although the epoxy resin has good adhesive properties, electrical insulating properties and chemical stability, but its brittleness and high water absorption rate make it hard to meet the requirement of the matrix resin making for high performance composite materials, and therefore modification is needed. Polyimide is excellent in mechanical and electrical properties. If polyimide is used to modify epoxy resin, both advantages can be integrated, and a matrix resin with high temperature and high toughness can be made. On the contrary, polyimide is refractory with insolublle which makes it hard to mix with epoxy resin uniformly, phase separation occurs easily. Reactive groups capped polyimide oligomers not only have excellent properties of the polyimide, but also have good dissolution properties, what is more, its chemical and physical structure can be easily designed, which make it modify epoxy resin effectively, and by structural design, a variety of different performance matrix resins can be prepared.This research topic is divided into four main parts:1. Synthesis and Characterization of2,2-bis[4-(3-carboxylphthalimidephenoxy)phenyl]propane (CIBAPP).2. Preparation and properties of E-51epoxy resin modified by CIBAPP.3. Preparation and properties of TGDDM epoxy resin modified by CIBAPP.4. Preparation and properties of high-performance composite materialsTo start with,2,2-bis [4-(4-aminophenoxy) phenyl] propane (BAPP) and trimellitic anhydride(TMA) have been used as the raw materials to synthesis CABAPP together with toluene and N,N-dimethyl acetamide as the solvent. FT-IR has been used to characterize the structure.Secondly, the mechanical properties, water absorption, viscosity, apparent activation energy, surface energy, and other properties were tested on E-51epoxy resin modified by different amounts of the freshly prepared CIBAPP solution. The studies showed that an increase in the amount of CIBAPP amount reduced the activation energy and enhanced the rate of the curing reaction, reduced the viscosity of the matrix resin, reduced the surface energy and water absorption rate in a certain range. When the CIBAPP amount was16phr, the matrix resin tensile strength was up to36.4MPa, the applicable period was750h and apparent activation energy was43.3kJ/mol, tensile strength retention rate was86%after1000h thermal aging, which indicates a kind of high performance matrix resin.The mechanical properties, water absorption, apparent activation energy, surface energy, and other properties were also tested on polyfunctional epoxy resin (TGDDM) modified by different amounts of the freshly prepared CIBAPP solution.The studies showed that when the CIBAPP amount was25phr, the matrix resin’s tensile strength was38.2MPa, the applicable period was more than400h and apparent activation energy was47.4kJ/mol, tensile strength retention rate was86%after1000h thermal aging, this combination of performance is excellent.From the results above the resins which had excellent mechanical properties, that is,16phr CIBAPP modified E-51epoxy resin and25phr CIBAPP modified TGDDM epoxy resin, were used to prepare two composite materials, and their mechanical, electrical, surface energy and other performance was tested. The study showed that the two composites had excellent mechanical properties:the flexural strength were609MPa and732MPa; good electrical properties:the breakdown voltage strength were33.7kV/mm and42.5kV/mm, respectively; the volume resistivities were1.1*1015Ω·cm and3.1*1015Ω·cm, respectively; the dielectric constant were4.9and4.1, respectively; good hydrophobicity:the surface energies were50.7mJ/m2and47.0mJ/m2, respectively, which is far less than the surface energy of water. Thus it can be seen that use modified epoxy resin as matrix resin and glass cloth as a reinforcing material, composite materials with excellent comprehensive properties can be obtained. |
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