Nanoencapsulated Lauric Acid with a Poly(methyl methacrylate) Shell for Thermal Energy Storage with Optimum Capacity and Reliability
Xiaosong Liu, Amy S. Fleischer, Gang Feng
Abstract
Organic phase change materials (PCMs) show much potential for thermal energy storage, but the liquid leakage tendency limits their practicality. This can be mitigated by encapsulation using a polymer shell. Fatty acids are promising for encapsulation due to the potentially strong bonding with the polymer shell materials to potentially enhance the overall thermal efficiency. Previous studies on encapsulating fatty acids are on the micro- or mesoscales, but in this study, the focus is on nanoscale encapsulation, which has the advantage of enhanced thermal conductivity. A nanoencapsulated poly(methyl methacrylate)-shelled lauric acid core system is created. The system has strong performance characteristics: high latent heat (up to 130 J/g) and particularly excellent thermal reliability (over 2000 cycles). Moreover, by changing the surfactants, the PCM capsule size can be tuned between 400 and 1000 nm with a shell thickness range of 20–100 nm. Controlling of molecular diffusion and flow is potentially the dominant mechanism for greatly enhancing the reliability of nanoencapsulated energy storage materials. Furthermore, infrared spectroscopy (IR) is proved to be a fast search tool to test the PCM encapsulation conditions. Conventionally, differential scanning calorimetry (DSC) is used to evaluate the PCM encapsulation. Compared to DSC, the IR-based technique is much faster (<1.0 min), requiring a minimal sample amount (<0.1 mg), and is consumable-free. Thus, the IR-based technique could help greatly speed up the finding of optimal conditions for fabricating high-performance encapsulated PCMs.