Preparation And Microencapsulation Of Bis-Ester Type Phase Change Energy Storage Materials

Phase change materials（PCMs）are materials that can absorb,store and emit large amounts of thermal energy at specific phase change temperature points using the transformation process of the phase.The development of heat storage phase change materials with different operating temperature ranges,non-toxic,high latent heat and thermal stability has been the focus of research.Since fatty acid esters have a high latent heat and good thermal stability,and because diesters have higher thermal stability and lower phase transition temperatures than related monoesters with the same carbon chain length,a series of 1,4-butanediol ester PCMs with high latent heat and thermal stability were synthesised in this study based on the esterification of 1,4-butanediol and fatty acids,The obtained PCMs have a phase transition temperature range of 30～80℃,a latent heat of 240 J/g and a volatilisation temperature of over 250℃.It shows that the diester PCMs can be used in a wider temperature range with good thermal stability.The synthesised ones are therefore suitable for use in thermal management systems.To solve the problems of leakage and low thermal conductivity of PCMs,the synthesised 1,4-butanediol ester PCMs were microencapsulated for thermal management applications.As well as considering the appropriate phase change temperature for device overheating protection,Octadecanoic acid 1,4-butanediyl ester was selected and silicon dioxide was chosen to coat it to prepare phase change microcapsules（MPCMs）and apply them in electronic device overheating protection.The MPCMs achieved a high encapsulation rate of 88.4%and a latent heat capacity of211 J/g.After 50 consecutive heating and cooling cycles,the thermal storage capacity was maintained at more than 98%,demonstrating excellent thermal cycling stability.the MPCMs have a thermal conductivity of 0.39 W m^-1 K^-1,a large increase relative to the PCMs due to the good thermal conductivity of the silica shell.In overheat protection applications,a significant thermoregulation effect was observed on MPCMs treated semiconductor cooling chips,effectively reducing the effects of overheating in electronic devices.The results show that MPCMs can provide effective temperature regulation and thermal management performance as a passive thermal management system.Also based on the needs of alpine scenarios,photo-thermally responsive phase change microcapsules were investigated.In this study,photothermal conversion phase change energy storage microcapsules were prepared using dodecanol tetradecyl ester as the phase change material as the core material,melamine formaldehyde resin（MF）as the shell and nano-Cu S as the Pickering stabiliser and photothermal material.Spherical Cu S particles with a diameter of approximately 10 nm were first synthesised by a facile hydrothermal reaction,and stabilised Pickering phase change material emulsions were produced under certain emulsification conditions using them as stabilisers.The results show that the MPCMs have a well-defined core-shell structure with an average size of about 7μm,as well as a latent heat of up to 180.3 J/g and an encapsulation efficiency of 81.36%,and after 50 consecutive heating and cooling cycles,the thermal storage capacity is maintained at more than 98.3%,showing excellent thermal cycling The thermal cycle stability is excellent.Meanwhile,the thermal conductivity of the microcapsules increased by 115～254%compared to the nuclear material due to the hybrid shell filled with Cu S nanoparticles.The photothermal conversion capacity of the synthesised microcapsules was measured and calculated to be up to 85.6%,thus enabling photovoltaic phase change energy storage at low temperatures by inducing passive thermal cycling through photothermal effects.This study provides a theoretical basis for the application of photovoltaic energy storage microcapsules in fabric warming,solar hot water systems and solar thermoelectric systems.