| In this paper, infrared-laser stealth coating was prepared with freshly prepared polycarbonate-based waterborne polyurethane adhesive, freshly prepared composite particles of aluminum coated by chromium oxide (Al/Cr2O3) and additives such as dispersing agent, thickening agent, leveling agent, etc.A polycarbonate-based low-infrared emissivity of waterborne polyurethane adhesive was synthesized by the way of self-emulsification method using polycarbonate diols (PCDL) as soft segment, isophorone diisocyanate (IPDI) as hard segment, dimethylol propinic acid (DMPA) as hydro-chain-extemder, triethylamine as neutralizer and ethylene diamine as small molecule chain extender. The effects of PCDL/IPDI ratio, the hydrophilic chain extender, neutralizing agents, and secondary chain extender agents on the stability and viscosity of the emulsion, infrared emission rate and water absorbency of the films were studied. Structure and infrared emissivity of polyurethane characterized by Fourier transform infrared spectroscopy (FT-IR) and infrared emissivity tester. The results showed that Synthetic latex adhesive which could be applied to the stealth coating was infrared transparent in the8-14μm band, infrared emission rate could be as low as0.825and the adhesive film had better comprehensive pro per ties when PCDL/IPDI ratio was2.5:1, the mass percent of DMPA and TMP were6%and1.5%of the total monomer, the degrees of neutralization were100%and ethylenediamine was controlled that the ratio of-NH3and-NCO was1.5:1.Composite particles of aluminum coated by chromium oxide were prepared by the way of hydroxide precipitation and calcination method using chromium trichloride, aluminum, and ammonia as the main raw material. The effects of mass ratio of Al and Cr2O3, dispersed manner, type and amount of dispersant, reaction temperature, reaction time and reaction pH on optical properties of coated particles were studied. Optical properties and structure of coated particles were measured by FT-IR, infrared emissivity measurement instrument, XRD, tunable CO2laser instrument and SEM. The results showed that the reaction system was stable, aluminum coated by chromium oxide completely and had low infrared emissivity and laser reflection performance which could be applied to the stealth coating as filler when mass ratio of aluminum powder and chromium oxide in coated particles was1:1.2, a dispersing agent was sodium hexametaphosphate and amount of it added was8%of the amount of aluminum powder, ultrasonic dispersing was chosen, reaction temperature was60℃, reaction time was4hours, pH of reaction system controlled to7.The infrared-laser stealthy coating was prepared by the way of coating on the glass, natural drying and using chromium oxide coated aluminum composite particles (Al/Cr2O3) as filler, polycarbonate-based waterborne polyurethane as adhesive. Effects of adhesive, filler and the amount added them into the coating on infrared emissivity and laser reflection properties of the coating were studied. Infrared emissivity at spectral range of8-14μm, laser at spectral range of10.6μm reflection performance and structure of the coating were measured by infrared emissivity measurement instrument, tunable CO2laser instrument and SEM. The results showed that infrared emissivity of adhesive used in this coating was low compared with ordinary waterborne polyurethane. Infrared emissivity and reflected laser energy of the coating decreased with the increase content of composite particles, when the binder added was a certain amount. Infrared emissivity could be reduced to0.688, energy reflected back accounted for only1%of the initial incident laser energy, when the composite particles added was30%. The coating had better comprehensive properties and reached the requirements of the IR-Laser composite stealth. |
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