Supercooling elimination of paraffin phase change material microencapsulated by poly(methyl methacrylate) and its thermal characterisation

Abstract Paraffin-type phase change materials (PCMs) were entrapped using poly(methyl methacrylate) (PMMA) by suspension polymerisation for heat storing purposes at room temperature. To reduce the supercooling of the entrapped RT25HC paraffin, organic PCMs with different melting points were used as nucleating agents, i.e. RT35HC (melting point: 35 °C), MOL62-66 (melting point: 62–66 °C) paraffin and hydrogenated beef tallow (HBT) (melting point: 55–61 °C). Morphology, particle size distribution and degree of supercooling were investigated, and special attention has been paid to thorough thermal analysis. The prepared particles were compared with commercially available Micronal DS5038X microcapsules. The different rotational phases and solid–solid transitions have been analysed. The heat content of the characteristic transitions of different paraffins occurred at temperatures well below their melting points, and hence, it does not affect their applicability. However, knowledge of the rotational phase transition of mixtures and microencapsulated products near the main peak of the DSC curves is important from a practical point of view, since the formation of mixtures and subsequent microencapsulation together resulted in a substantial loss of heat capacity. HBT as, a novel, renewable and inexpensive nucleating agent was explored and found to be an effective compound to minimise the supercooling of microencapsulated paraffin. Avoiding supercooling is necessary to exploit the latent heat capacity of the capsules under real operating conditions.