Study On Preparation And Damping Properties Of Polyurethane Microcapsules

With the development of transportation, aerospace and industrial undertakings, it’surgent to solve the noise problem. The basic principle of damping materials is to makeuse of the inherent ability of certain materials to absorb the vibrational energy, therebyproviding passive energy dissipation. Vibration damping is valuable for structures,enhancing the reliability and performance of structures. Damping material has avariety of classification and is widely used for noise reduction, especially in the fieldof automobile, aircraft and other transportation and military, with good developmentprospect.In this paper, the application of microencapsulation technology was envisaged intodamping materials. Currently, the rapid development of microencapsulationtechnology led to the diverse application fields. With the characteristics ofmorphology diversity, microcapsules could be used as fillers mixed into material. Ourwork was to clarify the issue whether the existence of microcapsules could improvethe damping performance of materials.Microencapsulation technology was applied to package all or part of the silicone oilinto microcapsule, when the microcapsules vibrated along with the externaloscillation, the viscosity property of the silicone oil and the friction between oil andthe inner shell wall made it possible for microcapsule to convert vibration into otherforms of energy, so as to achieve the effect of noise vibration reduction. In the second chapter, the interfacial polymerization was used to preparehomogeneous microcapsule with polyurethane-polyurea shell and methyl silicone oilas the core. Microcapsule’s preparation conditions were optimized to gethomogeneous microcapsule. The diameter of the microcapsules was8μm. A seriesof analysis was conducted using thermal gravimetric analyzer (TGA), scanningelectron microscope (SEM) and fourier transform infrared spectrometer (FT-IR) tocharacterize morphology, structure, thermal stability and permeability of themicrocapsules. The analysis proved successful preparation of double-shellmicrocapsules with part of silicone oil as the core. Then we used dynamic mechanicalanalyzer (DMA) to test material’s damping capacities and foundpolyurea-polyurethane incorporation microcapsules could improve the dampingproperties of the material of epoxy resin, maximum of loss factor (tanδ) raising from0.3653to0.5213. Microcapsules’ damping properties were related to the core volumefraction and the mass percent of microcapsules mixed into epoxy resin E51. Whencore volume fraction was37%and mass percent of microcapsules mixed into epoxyresin was2%, the material showed a best damping performance.In the third chapter, in order to increase the strength of microcapsules and improvetheir damping properties, hydrophilic silica was added into aqueous phase, Theresidual hydroxyl groups of hydrophilic silica’s surface reacted with isocyanategroups (-NCO) to produce a cross-linked structure during the reaction of interfacialpolymerization. After optimizing the conditions, we got uniform-sized microcapsules,diameter ranged from10to15μm. The damping capacities of pure epoxy resin andepoxy resin mixed with microcapsules were tested by dynamic mechanical analyzer. Itwas found that the epoxy resin mixed with microcapsules can indeed improve itsdamping properties, maximum of tanδ reached0.7225at a frequency of1Hz with ahigh damping temperature region ranged from107to131℃. The new hybridmicrocapsule had higher damping effect for materials than polyurea-polyurethanemicrocapsules. The epoxy resin would exhibit a best damping performance when corevolume fraction was20%, maximum of tanδ could reach1.19.