Study On Self-Healing Material With Epoxy-Containing Microcapsules Under The Variable Temperature Field

Cryogenic propulsion system have high specific impulse, low repeated start times, for long-term storage space requirement well meet the space task, so the cryogenic propulsion system has become the research focus of future spacecraft power system. However, cryogenic propulsion composite pressure vessels (COPVS) used by the system reliability and reusability problems worthy of attention, especially in the low temperature process. The micro crack damage as the material properties of the fuse, micro cracks will affect the mechanical properties of materials, including making the strength, hardness and other properties greatly reduce. In addition, micro cracks will lead to the gas permeability and leakage, which limits the application of COPVS can be repeatedly used in the future on the means of transport. In this paper, through the design of a self-healing materials with microcapsule, realizing the self-healing in variable temperature field, the self-healing materials has wide application prospect in future aerospace field.The work of this thesis based on the microcapsule synthesis and surface modification. Preparation of self-healing microcapsules with urea formaldehyde resin as wall material, epoxy resin E-51as core material by in-situ polymerization. On the basis of the microcapsule surface modification, analyze the KH550processing principles of micro capsule surface and the specific experimental methods, and Infrared Radiation (IR) spectra of the micro capsule after KH550treatment, X ray photoelectron spectroscopy (XPS), show that KH550encapsulated in microcapsules surface. The carbon nanotubes for acidification, proved by XPS characterization method that we have introduced-COOH on the surface of carbon nanotubes. The carbon nanotubes are grafted on the surface of microcapsule, by the XPS and SEM, we confirm the carbon nanotube are added to the surface of microcapsule.In order to make the material achieve self-healing function in variable temperature field, We need to choose a suitable latent curing agent. In order to make the material has a longer shelf life under low temperature, through analyzing the curing mechanism of latent curing agent, we ultimately determine using2MZ-Azine as the latent curing agent. The self-healing contains the repair agent of microcapsules and latent curing agent2MZ-Azine. The healing efficiency of the self-healing system is tested in a pure epoxy resin matrix. The results of static mechanical properties under low temperature shows that microcapsules grafted on the surface of carbon nanotubes have small mechanical properties, untreated microcapsules influence mechanical performance of matrix material more. Contrasting the three different sample preparation of microcapsules by self repair efficiency test, the results show that the repair efficiency of surface grafted carbon nanotube microcapsule and the use of KH550treatment of the prepared microcapsules specimens under cyclic temperature field difference, in micro capsule content is12%, when2MZ-Azine content is2%, self repair efficiency can be achieved-80%, self repair efficiency is poor and the surface without microencapsulation processing can provide, in the best content, self repair efficiency is about65%. The micro capsule surface grafted carbon nanotubes, effectively improve the repair efficiency of alternating temperature field in doped microcapsule self repair materials.