Epoxy resin is one of the most widely used thermosetting resins. However, the cured material has high brittleness and poor heat resistance, and it is difficult to meet the requirements of the ever-growing engineering technology, which limits the further application of the epoxy resin. Therefore, it is of great significance to improve the heat resistance of epoxy resin and its composite materials.
Epoxy resin was selected as the matrix and modified by physical and chemical methods. The physical and chemical characteristics of the composite resin matrix were characterized by modern analytical techniques. The epoxy resin was modified by bismaleimide to form a high temperature resistant composite resin matrix. The object of study was to study the composition and structure of the resin matrix, its curing properties, and its mechanical properties.
(1) Based on the bismaleimide (BMI)/epoxy resin ER (E-51)/diaminodiphenylmethane (DDM) composite system, the best ratio was determined by the mechanical properties test. 51: DDM=2:1 (mass ratio), BMI mass fraction was 30%. The curing reaction of BMI/ER/DDM system was investigated using FTIR, DSC and DMA respectively. The Kissinger method was used for the BMI/ER/DDM system. The curing reaction kinetics was studied and the theoretical curing temperature was simulated. The thermodynamic properties and dynamic mechanical properties of the cured product were studied by means of DSC, TG, DMA and SEM.
(2) Based on the bismaleimide (BMI)/phenolic epoxy resin EPN (F-51)/diaminodiphenylmethane (DDM) composite system, the optimum ratio was determined by mechanical properties testing. F-51: DDM=2:1 (mass ratio), BMI mass fraction was 35%. The curing reaction of the BMI/EPN/DDM system was investigated using FTIR, DSC, and DMA respectively. The Kissinger method was used for BMI/EPN/DDM. The curing reaction kinetics of the system was studied and the theoretical curing temperature was simulated. The thermodynamic properties and dynamic mechanical properties of the cured product of the system were studied by means of DSC, TG, DMA and SEM, and the BMI/EPN/DDM system and BMI were also studied. The /ER/DDM system was compared.
(3) The BMI/DDM/F-51 structural adhesive was modified with nano-silica particles as filler. And the addition of a silane coupling agent KH-560 surface modification of the filler. FTIR spectra confirmed that KH-560 was effectively grafted onto the surface of nano-silica, and the effect of the amount of filler and the amount of coupling agent on the mechanical properties of the matrix was examined and the optimum values ​​were obtained.
The study found that the addition of inorganic nano-silica has a great influence on the heat resistance and mechanical properties of the adhesive. The dynamic mechanical energy spectrum (DMA) and thermogravimetric analysis (TGA) characterize the heat resistance of the modified adhesives. The nano-silica increases the glass transition temperature and the thermal decomposition temperature from 209°C and 307°C to 214°C and 330°C, respectively. Nano-silica improves the mechanical properties.
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