| Fatty acid phase change material(PCM) had many superior properties, including the high latent heat of melting, the low degree of supercooling, non-toxic, non-flammable, excellent chemical stability and good compatibility with construction material, etc. Application of fatty acid in the building by using latent heat storage can reduce the temperature fluctuation range in a room and improve the comfort of the indoor environment as well as take effect in energy efficiency and environmental protection. Therefore the fatty acid PCM had become a focus in the field of building energy efficiency. This research contains the following several major topics:(1)Based upon schrader equation and the lowest eutectic point theory, capric-palmitic acid eutectic mixture(CA-PA) was selected as a type of PCM for building energy efficiency.The fatty acid eutectic mixture was prepared through melt-blending and combining ultrasonic oscillations. The differential scanning calorimetry(DSC) results indicated that the eutectic mixture was composed by capric acid(CA) and palmitic acid(PA) in the ratio of 0.82∶0.18(by mass). As the test results of DSC figure, the phase change temperature was 26.29℃ and the phase transition enthalpy was 140.36 J/g.( 2) A kind of microcapsule was prepared using CA-PA as core material and urea-formaldehyde resin(UF) as shell material via in-situ polymerization. Some important parameters such as emulsifier type, emulsifier amount, emulsifying time and emulsifying rate as the critical affective factors on encapsulation ratio and mean diameter of microcapsule were investigated extensively. The optimal emulsification conditions contained that,emulsifier type was AEO-7/Tween80 emulsifier with 12.86 of HLB value, emulsifier concentration was 4% of the core material quality, emulsifying time was 60 min and emulsifying rate was 1400 r/min.( 3) Some important parameters such as prepolymer concentration, mass ratio of core/shell material, aggregation speed and aggregation time as the critical affective factors on encapsulation ratio and mean diameter of microcapsule were also investigated extensively.The optimal synthesis conditions contained that prepolymer concentration, mass ratio ofcore/shell material, aggregation speed and aggregation time was 35%, 1.1∶1, 500 r/min and 3h, respectively through single factor and orthogonal experiment. The DSC, laser particle analyzer, fourier transform infrared(FT-IR) and other equipment were utilized to characterize the thermal properties, particle size, structure and so on of the microcapsule. The results showed that the phase transition enthalpy was about 106.79 J/g, the encapsulation ratio was about 76.08%, the phase change temperature was 27.32℃, and the mean particle diameter was 37.25 μm. All of the conclusions indicated that the microcapsule had good phase change heat storage function, good thermal performance and thermal cycling stability.(4)Phase change gypsum wallboard was made with the CA-PA/UF microcapsule as PCM and gypsum powder by direct addition method. The thermal performance, heat storage performance and cycle stability of phase change gypsum wallboard were also studied. The results showed that the phase change temperature of PCM, which was about 27℃, was not changed with the incorporation into gypsum powder. With 30% CA-PA/UF microcapsule in phase change gypsum wallboard, the phase change temperature and enthalpy was 27.24 ℃and 44.59 J/g, respectively. After 40 times thermal cycling, no leaking was found and the heat storage performance of phase change gypsum wallboard was essentially the same, which showed a relatively good thermal reliability. The performance of phase change gypsum wallboard generally meets the application requirements of the building energy efficiency. |
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