Preparation And Characterization Of Microencapsulated Ethylene Diamine

As is well known, it is incredible that polymer matrix composites will appear micro-cracks inside the material or on the surface of it due to its long use time, leading all aspects of materials performance greatly reduced, so repair the material damage timely is essential. In present the research in microcapsules self-healing composite material is mainly focus on curing agent of moderate activity, while the active curing agent of aliphatic amine curing agent has not been much developed. If the aliphatic polyamines can be successfully coated, then this paper can ensure that the polymer matrix composites are cured at room temperature, which is of great significance for the timely repair micro-cracks inside the material. This paper use ethylene diamine as the core material of the microcapsule to solve this problem. The polymer matrix composites doped with self-healing microcapsules has a great potential development and wider application in the aerospace, aviation.In this paper, the dual self-healing system contains the epoxy resin microcapsules and ethylene diamine microcapsules. The two kinds of microcapsules are dispersed in the resin matrix, when the crack grows to the microcapsules; they are fractured and release the core material of epoxy resin and ethylene diamine. As ethylene diamine encounters the epoxy resin, the polymerization occurs at room temperature, and the polymers joint the crack surface, to achieve self-healing. Because the polymers are same with the substrate material, making the crack at the interface of bonding well matched.This dissertation is based on the synthesis of epoxy resin microcapsules. This paper prepares the microcapsules with epoxy resin as shell material and ethylene diamine as core material by interfacial polymerization. Because the wall material of microcapsule is the same with the matrix material, the bonding is strong enough between the microcapsule and the resin matrix. In term of this theory this paper first designs the synthesis mechanism of micro-capsules, and then synthesizes the epoxy resin - ethylene diamine microcapsules,and does infrared spectroscopy (IR) analysis, surface morphology (SEM) analysis, thermal stability, particle size analysis and permeability analysis. Microcapsules used in the self-healing epoxy composite materials are tested.The experiments prove that the best core-wall ratio is 1:5, stirring speed is between 200~250r/min, reaction time is 24 hours and emulsifier is Span80 and Tween80. Under the best preparation conditions, the average particle size of microcapsules is about 400μm, distribution scale is between 180 and 620μm. The microcapsules are spherical or ellipsoidal, multi-core structure, the surface dense and smooth. The shell material of microcapsules is porous structure, and has certain permeability. The yield of microcapsules comes up to above 95%. Microcapsules have nice thermal stability under 50℃. Ethylene diamine coated in microcapsules is still active. Weight of microcapsules reduce 8.14% under 50℃after 6 hours.This paper embedes epoxy resin - ethylene diamine microcapsules and urea formaldehyde resin microcapsules in epoxy resin specimens, and then does the tensile test to measure the fracture toughness, and then along the crack recovers the specimen some time, making it self-heal the crack, and then does the second tensile test, measuring the fracture toughness after their self-repair, then compare the change of mechanical properties to characterize the repair efficiency of microcapsules.