Phase-Change Composites Composed of Silicone Rubber and Pa@SiO2@PDA Double-Shelled Microcapsules with Low Leakage Rate and Improved Mechanical Strength.

A kind of silicone rubber (SR)/paraffin (Pa)@silicon dioxide (SiO2)@polydopamine (PDA) phase-change composite was prepared in this work. The double-shelled Pa@SiO2@PDA phase-change microcapsules were constructed by oxidative self-polymerization of dopamine (DA) in Tris-HCl buffer solution. The effect of the DA content on the properties of Pa@SiO2@PDA microcapsules and SR/Pa@SiO2@PDA composites was researched. Due to the protective effect of SiO2, PDA layer, and SR matrix, the SR/Pa@SiO2@PDA composites have good leak-proofing performance, and the leakage rate of SR/Pa@SiO2@PDA-2 is as low as 0.45%. Phase-change enthalpies of the Pa@SiO2@PDA microcapsules and SR/Pa@SiO2@PDA composites are reduced slightly with increasing DA content. Meanwhile, the composites displayed improved mechanical strength. The tensile strength of SR/Pa@SiO2@PDA-2 can be up to 0.560 MPa, which is 1.85 times higher than the tensile strength of pure SR/Pa@SiO2 because the interface compatibility between Pa@SiO2 microcapsules and SR is improved through hydrogen bonding between the abundant groups on the PDA surface and the matrix. Moreover, the rough surface of the PDA-modified microcapsules also enhances the interface interaction through physical "interlocking". The new kind of SR/Pa@SiO2@PDA composite can be used for thermal management.