Preparation And Characterization Of Microcapsules Containing Phase Change Temperature Adjustable Binary Cores

Phase change materials (PCMs) have a good application value as thermalenergy storage materials. Microencapsulated phase change materials(micro-PCMs) make PCMs more widely available. Using differentpolymerization methods, a series of micro-PCMs are prepared which containingparaffin and butyl stearate as their binary cores. The phase change temperatureof these micro-PCMs could be adjusted by regulating the composition of thebinary cores, and the melting peak temperature of the micro-PCMs could beregulated from28oC to35oC.First, the phase change properties and chemical structures of the binarysystems are studied. The binary systems composed of paraffin and butyl stearatedisplay excellent phase change performances. The binary systems respectivelyshow one melting and freezing peak during solid-liquid phase transition process.Besides, FT-IR results indicat that paraffin and butyl stearate do not react with eachother, and the binary core materials exist as physical mixtures.Second, the binary cores are microencapsulated using polyurethane oracrylate-based co-polymer shells, the preparation process and phase changeproperties of these micro-PCMs are studied. Using interfacial polymerizationmethods, polyurea/polyurethane double shell micro-PCMs containing paraffinand butyl stearate are synthesized. Using butyl stearate that functionalizes as:co-solvent for improving compatibility of the paraffin and PU shell; componentof binary core for regulating phase change temperature in the range from28to35oC. The microencapsulation ratios of these as-prepared micro-PCMs are morethan60wt%. Moreover, in order to improve the thermal stabilities and thermalreliabilities of these microcapsules, four kinds of acrylate-based cross-linkingagents are respectively introduced into the microencapsulation process. After500times thermal cycling test, these as-prepared micro-PCMs keep goodstabilities that the microencapsulation ratio loss of the best-performedmicrocapsules are only about1wt%.In addition, octadecyl methacrylate and dodecyl2-methylacrylate are respectively introduced to form binary or ternary systems with paraffin and butyl stearate. Thermalproperties of these mixtures are investigated. Moreover, these binary or ternary systemsare microencapsulated with P(MMA-co-DVB) shells. Since different compositions ofthe core and shell materials, a series of microspheres are synthesized with the diameterranging from10μm to80μm, and the melting enthalpy is in the range of30J/g to65J/g.All the results reveal that the paraffin/butyl strearate micro-PCMs with different shellmaterials have good application value as thermal energy storage materials. The phasechange temperature of these as-prepared micro-PCMs not only could be adjusted byregulating the composition of their binary core, but the micro-PCMs show good thermalreliability after500times thermal cycling test.