| Traditional foam plastic has low density, with bad mechanical properties, and also, it's difficult to control the processing parameter. In order to cover its shortage, the thesis uses two kinds of polymeric microspheres to fill the epoxy resin to synthesize syntactic foam respectively. The syntactic foam has the density of 0.535g/cm3 and good mechanical properties. It could be used in the occasions where low density and good mechanical properties are required together.The mechanical properties of syntactic foam were studied as a function of the volume fraction (V_f) and particle size of the phenolic microspheres. Also, the effects of curing agent (2-ethyl-4-methylimidazole, EMI-2,4 and B) and reactive diluent (n-butyl glycidyl ether, BGE) on the mechanical properties of the syntactic foam were studied. The experimental results indicated that with the increasing of V_f, the tensile strength, tensile modulus, flexural strength, flexural modulus, flexural break percentage elongation and impact strength were all decreased. As the particle size of the microspheres increased, the density and the mechanical properties of the syntactic foam decreased. The addition of BGE could improve the flowing property of the system effectively, and has little influence on the mechanical properties when the content of BGE was less than 20% (mass fraction).It was found that the density and the void content of the syntactic foam were the function of V_F. With the increasing of V_f, the density of the syntactic foam decreased linearly, while the void content increased non-linearly. The experimental density had a little deviation from the theoretical density. The preparation technology impacted on both density and void content of the syntactic foam.Morphology and failure features of the syntactic foam were analyzed by SEM, and the failure mechanism was investigated. From SEM photographs, the syntactic foam had a three-phase structure including resin, microspheres and void. Through the SEM photographs of the fracture surfaces, it was found that when V_f <30%, fracture of the syntactic foam was caused by the break of the interface between the resin and the microspheres. When V_F >30%, several factions contributed to the fracture, among whichthe reduction of the adhesion between the resin and the microspheres brought by the accumulation of the microspheres was the main reason.VDC-AN-St copolymer microspheres with multi-bubble structure was synthesized and filled into the epoxy resin to manufacture syntactic foam. It was found that there was something different from that of phenolic microspheres: When M_f<5%, little effect of M_f on the flexural and impact strength was observed;while when M_F>5%, as M_F increased, the flexural and impact strength decreased greatly.B/EMI-2,4 curing system was identified as the curing agent, and the optimized curing condition was also decided. The apparent activation energy and the order of reaction were calculated by Kissinger equation and Flynn-Wall-Ozawa equation respectively. From the results of DSC, the exothermal temperature of the curing reaction advanced greatly as well as the exothermal time when B was added into the system. The initial temperature T_i, peak temperature T_p and termination T_F rose, and the exothermal enthalpy increased as heating rate acceletated.The microstructures and the mechanical properties of CTBN toughened epoxy resin and CTBN/bisphenol A modified epoxy resin were examined in order to overcome the brittleness of the the epoxy resin. It was found that the toughness of CTBN toughened epoxy resin increased while other mechanical properties declined. In the case of 120℃ pre-reacted for 2 hours, better CTBN toughening result could be achieved. When modified with CTBN/bisphenol A, the impact strength and the elongation to break increased dramatically, as well as other mechanical properties, which overcame the shortness of CTBN toughened singly. |
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