Effect of nanoparticle concentration on non-aqueous paraffin pickering emulsions in PEG400 for efficient thermal energy storage

Abstract

The development of non-aqueous phase change material emulsions (PCMEs) for thermal energy storage holds significant potential, as it enables the extension of the operating temperature range beyond the freezing and boiling points of water. Nevertheless, achieving stable and processable formulations remains a significant challenge. In this regard, this research presents the formulation and characterization of anhydrous Pickering emulsions, in which a selected paraffin (melting point 58–60 °C) serves both as the dispersed phase and as the phase change material (PCM), while polyethylene glycol (PEG 400) constitutes the continuous phase. The emulsions were stabilized with hydrophobized pyrogenic silica nanoparticles, and the influence of nanoparticles concentration on emulsion morphology, rheology, and thermal properties was evaluated. Characterization techniques included optical microscopy, steady-state flow measurements, oscillatory tests, and modulated differential scanning calorimetry (MDSC). The results demonstrate that the nanoparticles successfully stabilize the emulsions and enhance their rheological properties, which is attributed to internal structuring mechanisms. Additionally, only minimal supercooling was detected in the samples. Overall, the formulated emulsions exhibit tuneable properties and offer a promising platform for the design of PCME systems capable of stable operation at elevated temperatures, including applications in solar–thermal energy capture.