| Microencapsulated phase change materials (MicroPCMs) and nanoencapsulated phase change materials (NanoPCMs) are tiny vessels with phase change materials (PCMs). MicroPCMs are widely applied in aviation, space flight, mechanical manufacture, architectural materials, heat-storage and thermo-regulated textiles, and electronic devices. There are still knowledge gaps between fabrication and properties of nano- and microencapsulated phase change materials. The present research has investigated improving their thermal stability and preventing them from super-cooling in order to fabricate MicroPCMs and NanoPCMs with higher performances.MicroPCMs and NanoPCMs were synthesized by encapsulating n-octadecane and the other components within the melamine-formaldehyde (abbr. MF) resin shell through in situ polymerization. Their properties have been investigated by using Scanning Electronic Microscopy (SEM), Differential Scanning Calorimetry (DSC), X-ray Diffraction (XRD), Thermogravimetry-Differential Thermal Analysis (TG-DTA), Infrared Spectroscopic Analysis (IR), and Gas Chromatography (GC), etc. The effects of the mulser's stirring rate and the emulsifier concentration on the properties of encapsulated PCMs have been systematically studied, and NanoPCMs have been obtained by increasing the stirring rate or the emulsifier concentration. The influences of different nucleating agents on MicroPCM performances have also been investigated in detail to search for a suitable nucleating agent to prevent MicroPCMs from super-cooling. In addition, the impact of cyclohexane on MicroPCMs and NanoPCMs has been studied at length. Fortunately, their thermal stable temperature has been improved by feeding cyclohexane with an appropriate content to n-octadecane. The conclusions are showed as follows.1. Nanocapsules with 0.9 m in the weight-average diameter and 0.8 m in the number-average diameter have been obtained when the stirring rate of the mulser is 9000rpm and the TA concentration is 1.2%. As the stirring rate increasing, the average diameter of capsules decreases exponentially and its distribution turns narrow, but its polydispersity index increases.2. The mulser's stirring rate has no effect on the core content of capsules. The shell thick is linear with the average diameter of capsules while the weight proportion of the shell to the core is constant. The shell thick decreases with the increase of the stirring rate.3. For encapsulated PCMs with less than 10 m in their average diameter, their temperature and heat of phase transition seldom change as their average diameter decreasing; however, their crystallization peaks vary dramatically and the super-cooling becomes worse.4. When the TA concentration is 2.3% and the mulser's stirring rate is 8000rpm, nanocapsules with 1.0 m in the weight-average diameter and 0.9 m in the number-average diameter have been fabricated. As the TA concentration increases, the average diameter of capsules decreases exponentially. Simultaneously, its distribution gets narrow, and its polydispersity index decreases.5. The core content reduces as the TA concentration increasing; however, the shell thick changes slightly.6. Although the TA concentration hardly affects the phase change temperature, the heat of phase transition reduces as the TA concentration increasing. It scarcely influences the thermal stability of capsules.7. Sodium chloride has slight effect on the heat of MicroPCM phase transition, but it easily leads microcapsules to stick together. For the microcapsules feeding more than 6% sodium chloride in the emulsion, their super-cooling can be prevented availably; however, their mechanical intensity and their thermal stabilities turn worse and they cohere each other.8. 1-Octadecanol also affects slightly the heat of MicroPCM phase transition, but it easily induces microcapsules with MF resin as the shell to occur conglomeration. For the microcapsules with about 9% 1-octadecanol in the core, their super-cooling can al...
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