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Abstract A kind of silicone rubber (SR)/paraffin (Pa)@silicon dioxide (SiO 2) composite form-stable phase change material (PCM) was developed in this paper. Pa@SiO 2 was obtained by choosing Pa as PCM core microencapsulated in SiO 2 shell based on tetraethoxysilane (TEOS) and γ-aminopropyl triethoxysilane (APTES) as precursors, then Pa@SiO 2 microencapsules were embedded in SR matrix to fabricate SR/Pa@SiO 2 composites. The SiO 2 shell can provide a barrier for the melted Pa and meanwhile have reinforcing effect on SR as inorganic filler. The in-situ modification of SiO 2 shell using APTES owing to the amino groups can not only prevent agglomeration, but also increase interfacial bonding between Pa@SiO 2 with SR. The thermal and mechanical properties of the form-stable PCMs were characterized by differential scanning calorimetry (DSC) and mechanical tests. The results showed that the thermal and mechanical properties of SR/Pa@SiO 2 composites were better than those of SR/Pa and SR/Pa/SiO 2. Leakage test was conducted by heating the prepared composites over the melting temperature of Pa. The SR/Pa@SiO 2 composites were found as form-stable PCM with low leakage rate. The phase change latent heat of the SR/Pa@SiO 2 composites was up to 92.39 J g−1 and the composites can be used for thermal energy storage. Highlights • Developed a novel and efficient process for amino terminated paraffin (Pa)@SiO 2 microencapsules. • The Pa@SiO 2 microencapsules were embedded in silicone rubber (SR) matrix to fabricate SR/Pa@SiO 2 composites. • The SiO 2 shell can provide a barrier for the melted Pa and meanwhile have reinforcing effect on SR as inorganic filler. • The phase change latent heat of the SR/Pa@SiO 2 composites was up to 92.39 J g−1. [ABSTRACT FROM AUTHOR]

Abstract A series of paraffin/expanded graphite (EG) composites with various mass fraction were prepared. The microscopic geometry configuration, thermal conductivity and saturation sorption capacity of EG were obtained. In this paper, a method based on the experiments of EG pores was proposed for constructing geometric models. The geometric model constructed by this method has obvious anisotropy and has been employed in the calculation. Furthermore, the numerical results of thermal conductivity indicate anisotropy of a single-pore. Moreover, it had been observed by experiment that the anisotropy is weakened and transformed to isotropy in the process of combining geometric models with a large number of single pores. The final numerical results agree well with the experiments, which validates the precision and reliability of the proposed model. The increasement of thermal conductivity is also calculated and discussed during the phase change process of paraffin/EG. Highlights • A method of EG pores was proposed for constructing geometric models which has obvious anisotropy. • The SEM micrograph and saturation sorption capacity are employed to build the geometric models of EG pores. • Effective thermal conductivity during non-phase change process and the phase change process was calculated. • The numerical results agree well with the experiments. [ABSTRACT FROM AUTHOR]

Novel microencapsulated phase change materials (MEPCMs) with high encapsulation capacity and enhanced leakage-prevention performance were prepared by in situ polymerization. For these MEPCMs, paraffin and melamine-formaldehyde resin (MF) are respectively used as core and shell, and graphene oxide (GO) nanosheets, which can be seen as extra protective screen, are situated at the interface between the core and the shell. Effects of GO on morphology, microstructure and properties of MEPCMs were characterized by scanning electronic microscopy (SEM), laser diffraction particle analyzer, atomic force microscopy (AFM), Fourier transformation infrared spectroscopy (FTIR), X-ray diffractometry (XRD), transmission electron microscopy (TEM), differential scanning calorimetry (DSC), thermogravimetric analysis (TG) and paraffin leakage rate test. The results show that the fabricated MEPCMs with GO nanosheets have gradual increasing average diameters from 6.32 to 15.89 μm with an increase content of GO, while the size of MEPCMs without GO is 5.63 μm. When the time of leakage rate test is 50 h, the MEPCMs prepared with 0.5 mg/mL GO aqueous dispersion have considerably high encapsulation ratio of 93.9 wt.%, and the leakage rate is reduced by 93.1% compared with those without GO. The high encapsulation capacity and enhanced leakage-prevention performance might be highly attractive for the application of MEPCMs. [ABSTRACT FROM AUTHOR]

Thermally conductive form-stable phase change materials (FSPCMs) were prepared by using ethylene-vinyl acetate (EVA), paraffin, expanded graphite (EG) and carbon fiber (CF) as row materials. Two-dimensional EG and one-dimensional CF were used as thermally conductive fillers. Paraffin and EVA were phase change material (PCM) and supporting material, respectively. Differential scanning calorimetry (DSC) and leakage rate testing results indicated that FSPCMs owned the melting temperature of 45.63 °C and the latent heat of 167.4 J/g. The prepared material had a small leakage rate which was less than 2%. Scanning electron microscope (SEM) results shown that EG and CF possessed excellent compatibility in FSPCMs. In-situ X-ray diffraction (XRD) tests demonstrated that the crystal behaviors of paraffin and EVA were changed with the phase transformation. Thermal conductivity results shown that thermal conductivity of FSPCMs in horizontal orientation was higher than that in longitudinal orientation. EG and CF have synergistic enhancement to thermal conductivity of FSPCMs. [ABSTRACT FROM AUTHOR]