Ammonium polyphosphate (APP) exhibits high water solubility, mobility, and slow-release properties, which can greatly improve the utilization of phosphorus by alleviating soil phosphorus fixation. However, obtaining an efficient method of preparing APP that involves low energy consumption and production cost remains a challenge in current industrial production. Herein, by using urea phosphate (UP) as the main feedstock, we established a simple one-pot method for synthesizing highly water-soluble APP and explored the regulatory mechanism of the reaction temperature, the ratio of urea phosphate to monoammonium phosphate (MAP)/potassium dihydrogen phosphate (MKP), and the reaction time on APP performance. After analyzing the products obtained from different reaction conditions, we classified the polymerization process into the following stages: chain generation and chain growth. The chain generation reaction occurs simultaneously with the chain growth reaction, and the chain growth reaction tends to dominate with further reaction time. Furthermore, the optimum processing conditions for industrial production were obtained by comparing product performance, and the resulting APP products exhibit the following characteristics: the N and P contents were 20.6% and 58.8%, respectively, the polymerization rate (Pr) was 93.6%, the degree of polymerization was 4.22, and the solubility was 263.91 g/100 g H2O. Finally, to characterize the stability of the APP liquid fertilizer, we further investigated the hydrolysis behavior of APP and obtained the apparent activation energy (E a = 93.17 kJ/mol) of APP hydrolysis and the evolution of polymerization degree distribution of APP at different pH values. Overall, our results indicate that low temperature and alkaline conditions can greatly prolong the storage time of ammonium polyphosphate-based liquid fertilizers, which provides a basis to compound highly concentrated ammonium polyphosphate-based liquid fertilizers.

Inorganic hydrated salt phase change materials (PCMs) have the advantages of large latent heat, wide source range, and no poison, and they are widely used in the field of building energy conservation. In this study, sodium sulfate decahydrate (SSD) and sodium acetate trihydrate (SAT) were prepared into binary eutectic hydrated salt (EHS) by the melt blending method. The EHS was respectively impregnated into porous adsorption materials, such as attapulgite and expanded perlite, to prepare two shape-stabilized phase change materials (SSPCMs) by the vacuum impregnation method. The chemical structure, crystal phase, and combination mode of eutectic salts and SSPCMs were determined by Fourier transform infrared spectroscopy and X-ray diffraction techniques. The results show that there is no chemical reaction between porous adsorption materials and eutectic salt but a physical combination. Scanning electron microscopy results show that the eutectic is well-adsorbed in the porous structure of attapulgite or expanded perlite. Differential scanning calorimetry results show that, when the molar ratio of SSD/SAT is 0.71:0.29, the phase transition temperature of EHS is 28.5 °C and the phase transition enthalpy is 128.1 J/g. Borax (1.5 wt %) can effectively reduce the subcooling of binary EHS from 10.8 to 0.7 °C. Adding 25 wt % attapulgite can completely adsorb the PCMs; the phase change enthalpy is 92.1 J/g; and after 200 cycles, the enthalpy decreases by 24.6%. Encapsulated by polyurethane, the enthalpy value of SSPCMs only decreases by 10.4% after 200 thermal cycles, showing that the thermal stability is significantly improved.