Synthesis And Application Of Polyurea Phase Change Microencapsulation

Phase change material can be stored or released heat during a phase change process, thus regulating and controlling the environmental temperature. Such materials become national and international research focus of energy utilization and materials science, bacause it can solve the contradiction between energy supply and demand in time and space mismatch. The phase change can generally be classified into solid-solid, solid-liquid, liquid-gas and gas-solid according to the phase change mode. Although the latter two phase transition can store large quantity of heat, but gas has huge volume which makes the system bulky, equipment complicated and extremely difficult to use in practice. Therefore, the use of phase change process often has solid-solid and solid-liquid. Since the type of solid-liquid phase change material has the disadvantages of significantly phase change, so researchers take advantage of capsule technology to wrap phase change material which have specific melting point and crystallization point in recent years.A series of polyurea resin microcapsules containing a phase change material of n-octadecane was successfully synthesized by an interfacial polymerization, and the polyurea resin is generated by the reaction of oil-soluble monomer TDI and water-soluble monomer DETA. The influences of the ratio of oil and water, stirring speed and emulsifying time on the emulsifying effect and microcapsules performance were investigated. The results illustrated that the optimum conditions were the ratio of water and oil was 1:6, the stirring speed was 6000 r/min and the emulsifying time was 5min. Under the optimized conditions, the emulsion was uniform and stable and the value of d90 was 3.25μm, namely 90% of the microcapsules particle size under 3.25μm. The microcapsules were successfully synthesized respectively in the aqueous of sodium salt of styrene-maleic anhydride copolymer, OP-10 and gum arabic, then the diameter distribution, surface morphology, phase change properties and anti-permeability performance of the microcapsules were investigated. Results showed that the microcapsules which was fabricated with OP-10 as emulsifier were equipped with smaller particle size from 1μm to 4μm, more uniformity and better property of permeation resistance than the other microcapsules which was synthesized with sodium salt of SMA and gum arabic as emulsifier. The concentration of emulsifier affected performance of the microcapsules greatly. The microcapsules achieved a best property with smallest average diameter, narrowest size distribution and the least by products when OP-10 was employed in the amount of 8% to prepare microcapsules.The optimum molar ratio of TDI and DETA was measured by dry weight analysis method. The results confirmed that the optimum molar ratio of DETA and TDI was 1.29: 1. The FTIR and SEM picture of phase change microcapsules which were prepared in different polymerization time showed that the particle size of microcapsules were uniform, and with the extension of the polymerization reaction time, the number of microcapsules and balling rate increased, the surface of microcapsules was smoother and the shape of microcapsules was more regular, and when the reaction was carried out 3h, the reactants had been completely consumed. Finally, polyurea resin phase change microcapsules was successfully compounded under optimum operating conditions, and microcapsules performance were studied by differential scanning calorimeter, fourier transform infrared spectroscopy and thermo-gravimetry analysis. The FTIR spectrum proved core materials was wrapped by wall materials successfully. The TG curve indicated the wall materials of polyurea resin to some extent prevented the core materials of n-octadecane from volatilizing, and thermal stability of n-octadecane microcapsules were enhanced. The DSC test data revealed the enthalpy value of polyurea phase change microcapsules was 95.81J/g and the package efficiency was 92.13% which indicated that the phase change microcapsules were equipped with certain heat storage and release capacity and n-octadecane was fully utilized.In this paper, in order to test the thermostat ability of polyurea resin phase change microcapsules and melamine resin phase change microcapsules which were synthesized by senior fellow apprentice, the spray-bonded polyester wadding, silk-like polyester waddings and seven-hole polyester wadding with phase change microcapsules were finished by impregnation method, and the thickness, areal density, surface morphology, warmth and heating performance of the finished waddings and unfinished waddings were investigated. The test results demonstrated microcapsules aggregated and agglomerted on the wadding, wadding became thin, areal density increased and warmth retention ratio and insulation quality conversion rate augmented in a certain degree. The value of insulation quality conversion rate of the wadding which was finished with melamine resin phase change microcapsules was higher than that wadding was finished using polyurea resin phase change microcapsules, on the contrary, the value of insulation thickness conversion rate was almost unchanged or a little declining. The curve of time and temperature showed the temperature rise rate of the unfinished wadding was fastest, followed wadding finished with polyurea resin phase change microcapsules and the wadding which was finished with melamine resin phase change microcapsules could significantly regulate thermal. In the same time, it can also proved that the finished wadding was provided with the regenerative thermal control performance.