Relationship between cross-linking network structure and phase change performances toward multifunctional epoxy/bio-based wax form-stable phase change materials

• Effect of cross-linking network on enthalpy value of polymeric FSPCMs was revealed. • Polarity effect and steric hindrance effect greatly affect phase change properties. • Optimized CNT modified epoxy/beeswax PCM exhibits multifunctionalization. High encapsulation rate resulting from the good compatibility between cross-linking network and encapsulated solid–liquid phase change materials (SLPCMs) cannot necessarily result in high enthalpy value for the polymeric PCMs. However, the inner mechanism considering the above fact is not clear due to the lack of suitable model compound systems. In this work, a type of epoxy resin with crystalline alkyl side chains (named D18) and four types of amine curing agents (with similar structure but different polarity and molecular size) were primarily used as the model compound to achieve the encapsulation of beeswax (Bw, a kind of bio-based wax), and then the influence of the cross-linking network structure (using different curing agents) on the phase change performances of the D18/Bw polymeric form-stable PCMs (FSPCMs) was systematically studied. The results suggest that polarity effect and steric hindrance effect are the two factors that affect the phase change performances of the polymeric FSPCMs. Though the encapsulation rate of Bw is the highest (near 70 wt%) in the EP H-Y systems (using 1,3-Cyclohexanebismethylamine as the curing agent), it is the EP M-60 sample (using M−Xylylenediamine as the curing agent and containing 60 wt% Bw) that exhibited the highest enthalpy value of 146.2 J/g. Subsequently, different amount of multi-walled carbon nanotubes (CNT) was introduced to improve the thermal conductivity (TC) and achieve multifunctionalization of the EP M-60 sample. The TC, electromagnetic interference (EMI) shielding performance, and contact angle of the 30 wt% CNT modified EP M-60 sample can reach 1.37 W/mK, 37.4 dB, and 137°, while the enthalpy value can remain 101.1 J/g. This work is very helpful in clarifying the relationship between cross-linking network structure and phase change performances of polymeric FSPCMs, so as to providing theoretical guidance for the cross-linking network structure optimization in preparing other reliable polymeric FSPCMs with high enthalpy value, high reliability, and multifunctionalization.