Preparation Of Microencapsulated Phase Change Materials And Its Application In Thermal Infrared Stealth

Due to the generality of infrared ray radiation of the object, the diversity of infrared ray radiation for target and background and passivity of heat investigation, thermal infrared detection plays an important role in modern military reconnaissance, many military targets had been exposed in thermal infrared investigation. In order to avoid the military targets and weapons being found and destroyed by enemy, the most simple and effective way is to use thermal infrared stealth materials.Phase change materials can storage and release energy in the form of latent heat by their temperature remained. Microcapsule phase change materials (MCPCM) were synthetized by technical of microcapsule. For making false target, the infrared characteristic of true goal was passive simulated with the drive of environment temperature, which can achieve the purpose of thermal infrared stealth.In this research, the MF/paraffin MCPCM and MF/mixed n-Butyl stearate and n-Tetradecyl alcohol MCPCM were prepared with in situ polymerization by using Melamine-Formaldehyde (MF) resin as the wall material, and paraffin with different phase change of temperatures, n-Butyl stearate and n-Tetradecyl alcohol as core material. The surface of the MCPCM, thermal properties and chemical composition were characterized by SEM, DSC, FT-IR respectively. The SEM images showed that MF/paraffin MCPCM was loose with smooth surface, the structure is irregular spherical; The MF/mixed n-Butyl stearate and n-Tetradecyl alcohol MCPCM was also loose with smooth surface but a little indentation. The DSC results showed that the phase change temperature of MF/paraffin MCPCM was about51.3-58.1℃, its latent is114J/g; the phase change temperature of MF/mixed stearic n-Butyl stearate and n-Tetradecyl alcohol MCPCM was33.4-41.5℃, the latent heat was about154J/g. The initial phase change temperature of two kinds MCPCMs were higher than the core material, the latent heat of two MCPCMs were less than that of core material. Ft-IR results show that the MCPCM has been formed by using MF resin as wall material.The infrared stealth camouflage coatings were prepared with MCPCM as temperature control materials, hollow glass beads as heat insulation materials and the homemade hydroxyl acrylic resin as bond. According to the principle of infrared stealth requirement, the one-dimensional heat dissipation modeling was set up, the radiation exitances of the coatings at different temperatures were measured by the contactless infrared thermometer measurement and radiation rate test device. The Result Indicates that the best proportion for decresing the radiation exitances of the coatings is when the ratio of core and wall of the microcapsules are1:1and1.4:1, respectively for the wax paraffin microcapsules and mixed-core microcapsule,the ratio of two microcapsules is5:5. Being good for infrared stealth, Hollow glass beads has an outstanding heat insulation effect, which can reduce the temperature of coating itself and extend the time of phase change. With MCPCM used in phase change coating and hollow glass beads used in camouflage coatings, it’s the best way to use MCPCM and hollow glass beads in thermal infrared stealth camouflage coatings. By contrasting with ordinary camouflage coatings, the infrared stealth camouflage coatings has great control function of radiation exitances, which can effectively reduce the radiation characteristics of target. The rate of decrease can reach59%, which applied ways for infrared stealth with MCPCM.