Preparation And Characterization Of Capsule-type Self-healing Material With Fluorescent Damage Detection Function

In the process of using polymer materials,it is inevitable that they will be affected by external stress,light,temperature and other factors,so that the mechanical properties of materials decline or even scrap,so how to extend the service life of materials has been a huge problem facing people.Therefore,it is of important scientific and practical significance to maintain the mechanical properties of materials and extend the service life of materials.In order to solve this problem,the researchers designed self-healing cells inspired by biological.In the past 20 years,self-healing materials have been paid much attention by researchers,among which,microcapsulation self-healing materials have developed rapidly.In this study,epoxy resin mivrocapsules coated with urea-formaldehyde were synthesized by original polymerization method,and self-healing materials with epoxy resin capsules were prepared based on epoxy resin.Self-healing materials with fluorescence indicating function were prepared by selecting different fluorescent indicators.The main contents include as follow:Microcapsules with urea-formaldehyde resin as shell,epoxy resin and ethyl acetate as core were prepared by original polymerization.The chemical structure of epoxy resin microcapsule was characterized by Fourier transform infrared spectrophotometer(FT-IR).The surface morphology was observed by scanning electron microscope(SEM).The particle size distribution of microcapsules was observed by optical microscope(OM).The effects of different rotational speeds on the particle size of the microcapsule,the effects of different pH values on the formation of the microcapsule,and the effects of different core-wall ratios on the morphology of the microcapsule were discussed respectively,and the optimal synthesis process for the preparation of the epoxy resin microcapsule was determined.The results showed that the urea-formaldehyde resin was successfully coated on the epoxy resin,and the synthesized microcapsules presented regular spherical shape,rough surface and normal particle size distribution.The microcapsules obtained at pH=3 are more suitable for mixing in resin;When the ratio of capsule to wall was 1.5:1,the yield of microcapsule was the highest.The microcapsule has no mass loss and good thermal stability under 230?.By designing and synthesizing a new type of latent curing agent,the underwater selfhealing polymer composites with damage detecting were successfully prepared.This fluorescent latent hardener(FLCA),after being exposed to water,releases the amine group from which the amine group reacts with the epoxy resin to make the self-heal.Fluorescent dyes released underwater can visually indicate scratches and healing areas.The optimal ratio of microcapsule and FLCA was determined by testing the healing performance of selfhealing materials with universal testing machine.When the microcapsules with a mass fraction of 15% and FLCA with a mass fraction of 6% were embedded in the self-healing materials,the healing efficiency was 85.6%,and the fluorescence detection efficiency was the most obvious.The epoxy resin microcapsule containing tetraphenylene was prepared by mixing tetraphenylene with epoxy resin,and then the self-healing film with fluorescence indication function was prepared.According to the fluorescence spectrometer test,tetrabyethylene has no fluorescence before epoxy resin curing.Tetrabyethylene will emit fluorescence after the epoxy resin curing.Therefore,when the material is damaged,the leaked epoxy resin in the microcapsule reacts with the residual curing agent in the matrix to curing crack and making the damaged area emit blue fluorescence,thus indicating the damage location.The scratches of the self-repairing film were observed by SEM,and the optimal additive content of the microcapsule was determined to be 20%.