Preparation Of Pickering Emulsion-based Microencapsulated Self-healing Materials And Their Performance Study

Polymeric materials are used in aerospace,sports,construction,automotive,agriculture,fuel cells,electrical industry,etc.because of their high strength and ease of processing.During processing and use,microscopic cracks,which are not visible to the naked eye,inevitably occur,affecting the service life and mechanical properties of polymeric materials.For this reason,self-healing materials based on the damage-selfhealing mechanism of living organisms have attracted a lot of attention.Among them,microencapsulated self-healing materials have mature preparation processes,are highly designable,and have great potential for industrial production.The repair principle of microencapsulated self-healing materials is to add microspheres coated with repair agent to polymer materials,and the repair agent flows out after the microcapsules are broken to complete the repair of microcracks.However,the addition of microcapsules reduces the mechanical properties of the polymeric material.Intrinsic self-healing materials,which rely on intermolecular forces to achieve repair functions,can effectively avoid this.However,intrinsic self-healing materials have poor mechanical properties of the matrix and need to be stimulated by external conditions to complete the repair.The particle size of conventional microcapsules is in the tens and hundreds of microns,which can seriously affect the mechanical properties of polymer composites.In this paper,two polymeric self-healing materials based on Pickering emulsions are designed to address this problem.The experiments in this paper are as follows:(1)Epoxy microcapsules and amine microcapsules were successfully prepared by Pickering emulsion template method.The epoxy microcapsules and amine microcapsules were dried to prepare the epoxy self-healing composites.In addition,the surface morphology of the microcapsules and the self-healing materials before and after repair were characterized by metallurgical microscopy and scanning electron microscopy,and the test results showed that the average particle size of the epoxy microcapsules and amine microcapsules were 3.62 μm and 4.63 μm,respectively,and the self-healing materials had successfully completed the repair.The presence of the characteristic peaks of polyurea(PU)in the microcapsules was demonstrated by Fourier infrared spectroscopy,and the bilayer shell microcapsules have been successfully prepared.The thermal stability of the microcapsules was characterized using a thermogravimetric analyzer(TGA),and the test results showed that the encapsulation rate of epoxy microcapsules was 86.0% and that of amine microcapsules was 90.3%.The mechanical properties of the epoxy self-healing materials were analyzed,and the test results proved that the addition of microcapsules in this paper had a small effect on the mechanical properties of the materials,and when the microcapsule content was 10 wt%,the two-component self-healing materials still had more than 70%of the tensile stress,and the tensile stress after repair was 148% of that before repair.It has great potential for application in daily life and other fields.It is promising in extending the service life of materials and reducing the pollution and economic loss caused by the disposal of polymer materials.(2)Microcapsules with linseed oil as the restorative agent were prepared by polymerization of monomers at the interface between the aqueous and oil phases to form a shell material.The epoxy resin self-healing material was prepared by incorporating the linseed oil microcapsules into the epoxy resin matrix.In addition,the effects of different core-to-wall ratios,water-to-oil ratios,and GO water dispersions on the linseed oil microcapsules were investigated,and infrared spectroscopy,metallurgical microscopy,scanning electron microscopy,thermogravimetric analyzer,and universal testing machine were used to characterize the linseed oil microcapsules and the epoxy resin self-healing materials containing linseed oil.The test results showed that the linseed oil microcapsules had been successfully prepared and selfrepairing materials can complete the repair of damaged areas.The average particle size of flaxseed oil microcapsules was 3.88 μm,the encapsulation rate was 90.0%,and the thermal stability was good.The bending stress,tensile stress of the self-repaired material was improved when the content of linseed oil microcapsules was 2 wt%,which proved the toughening effect of small particle size microcapsules on the self-repaired material.At 5 wt% of linseed oil microcapsules,the tensile stress of the self-repair material before repair was 92% of that at 0 wt%,and the tensile stress of the self-repair material after repair was 130% of that before repair,at which time the self-repair material had both mechanical properties and repair properties,which was the optimum content.