Synthesis and characterization of polyethylene glycol/modified attapulgite form-stable composite phase change material for thermal energy storage

Attapulgite with a nanoporous structure is an excellent supporting material to solve leakage of polyethylene glycol (PEG). However, when raw attapulgite is used as a supporting material, the latent heat storage capacity of PEG/ raw attapulgite form stable composite phase change material (FSCPCM) cannot be fully utilized. In this work, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane (KH792) was initially modified attapulgite with amino groups firstly. A new form stable composite phase change material (FSCPCM) was prepared by adsorbing PEG into this modified attapulgite (N-ATP). The pore structure, leakage and thermal energy storage performance of this FSCPCM were investigated. Those results indicated that, compared to raw attapulgite, using N-ATP as a supporting material improved the crystallinity of PEG in the FSCPCM. Due to this improvement, the latent heat of the FSCPCM was significantly enhanced accordingly. Differential Scanning Calorimetry (DSC) measurements showed the latent heat of the PEG/N-ATP FSCPCM increased by 86.7% from the PEG/raw attapulgite FSCPCM and was close to the theoretical latent heat. Thermal conductivity analyses indicated the thermal conductivity of the PEG/N-ATP FSCPCM improved relative to of PEG. The thermogravimetric analysis (TGA), leakage testing and thermal cycling tests indicated that the PEG/N-ATP FSCPCM also had good thermal reliability, good thermal stability and leakage-proof performance. Moreover, relative to PEG/raw attapulgite FSCPCM, cement incorporated PEG/N-ATP FSCPCM has better heat storage capacity and strength.