| In order to reduce the fuel consumption per kilometer by reducing vehicle weight, so as to achieve resource conservation and environmental protection purposes, automobile Lightening has been a research focus in automobile industry. It’s necessary and critical to modify epoxy adhesives used in automobile lightening, as they need to meet high strength, good toughness, fatigue resistance, anti-aging and could bond dissimilar materials, and so on. Against the need to meet the performance requirements, we do the modified work from toughening, improving aging resistance, altering curing conditions and some other aspects.Firstly, chemigum toughened system and CTBN-modified epoxy resin system were studied. Compared with unmodified epoxy adhesive, tensile strength, bending strength and compression strength decreased slightly, while the impact strength, elongation and tensile modulus have improved when chemigun additive was10wt.%. When15wt.%CTBN-modified was mixed with epoxy resin and pure epoxy, toughening effect was obvious. The shear strength was31.26MPa, impact strength can reach21.82kJ/m". The curing reaction exothermic peak of the two systems were studied by differential scanning calorimetry. By Kissinger equation and Crane equation, we simulated and calculated:the curing reaction activation energy of the chemigum toughened system was53.35kJ/mol, reaction order was0.893; the curing reaction activation energy of CTBN-modified system was54.59kJ/mol, the reaction order was0.895.Secondly, the synthesis of polyurethane prepolymer and then modifying epoxy resin were successful. When50wt.%epoxy resin modified by polyurethane prepolymer was compounded with pure epoxy resin, the impact strength reach highly23.98kJ/m2, achieved88.2%increase over the previous unmodified. Observation of the fracture surface morphology of colloidal impact by scanning electron microscopy, there were a lot of roots branching cracks scattered, as apparent fracture toughness. When added in an amount of epoxy resin modified by polyurethane prepolymer, the shear strength achieve nearly40MPa, other properties were also slightly enhanced compared to single CTBN-modified epoxy resin.Finally, the heat resistance properties of five kinds of toughened system were investigated, the change of their glass transition temperature after the modification was insignificant, about80"C. In the anti-aging properties test,1wt.%coupling agent KH560can greatly reduce the degree of shear strength aging decline after boiled. For carbon fiber, aluminum and their mutual bonding of the five toughened systems, the materials were damaged, reflecting a good adhesive bonding properties.The five kinds of toughened epoxy adhesive systems developed in this thesis could be applied to the different needs of the automobile lightening, if they can pass the service performance test. |
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