Preparation and stability analysis of glycine water-based phase change materials modified with potassium sorbate for cold chain logistics

Organic water-based phase change material (PCM) shows great potential for cold chain logistics below 0 °C. However, its poor stability limits its application. The purpose of this study is to develop an organic water-based PCM with high latent heat and melting temperature of −4 °C to −6 °C based on solving the problem of poor stability. Glycine and mannitol aqueous solution were selected as the base PCM, and the static stability was improved effectively with 0.1 wt% potassium sorbate modification. The prepared 6-PCM5 composed of 6 wt% glycine, 1.5 wt% mannitol, and 0.1 wt% potassium sorbate, demonstrated moderate thermal conductivity of 0.6017 W/(m·K) and a suitable melting temperature of −5.78 °C as well as an enthalpy of fusion of 292.64 J/g. After 100 thermal cycles, the melting temperature, enthalpy of fusion, and thermal conductivity were −5.91 °C, 290.66 J/g, and 0.5886 W/(m·K), which decreased only by 2.24%, 0.68%, and 2.18%, respectively. Furthermore, the cold storage performances of 6-PCM5 and ice were compared and evaluated by loading strawberries. Compared with ice storage, the pre-cooling time and average temperature of strawberries in the cold storage box with 6-PCM5 was reduced by 68.4% and 2.55 °C, and the effective cold storage time was lasted for 22.83 h at a temperature range of 0.45 °C to 3 °C, which effectively improved the cold storage quality of strawberries. Overall, the developed 6-PCM5 cold storage material possesses good static and cyclic stability, providing an effective solution for pre-cooling and short-distance cold chain transportation of perishable food.