Thermal characterization of obtained microencapsulated paraffin under optimal conditions for thermal energy storage Samaneh Sami 1 • Nasrin Etesami 1 Received: 6 March 2017 / Accepted: 29 May 2017 Ó Akade ´miai Kiado ´, Budapest, Hungary 2017 Abstract The effective and facile microencapsulation of paraffin with poly(styrene) was conducted using emulsion polymerization. The optimal independent variables using response surface methodology were paraffin wax/styrene mass ratio of 0.39, SDS/styrene mass ratio of 0.032 and the stirring rate of 1500 rpm which are different from those of in the previous works. The thermal characterization of the optimal sample was carried out using TG and DSC analysis. Microcapsules produced using this method show less mass loss during the heating process. The microencapsulation ratio (ER) reached to 87.8 ± 0.2% under the optimal con- ditions. The morphology of the optimal microcapsules was considered by SEM analysis. The results showed that the obtained microparticles were smaller, smoother and have greater microencapsulation ratios than was the case for those produced in previous studies. Thus, the optimal encapsulated paraffin with the maximum ratio and good stability can be considered to have good potential for energy storage. Keywords Phase change materials (PCMs)  Microencapsulation  Latent heat thermal energy storage  Response surface methodology (RSM)  Experimental optimization Introduction There is always a time or space contradiction between energy supply and energy demand. Thermal energy storage (TES) can solve this contradiction by reducing energy consumption [1]. In recent decades, phase change materials (PCMs) have become important functional materials because they can store thermal energy and adjust their temperature by storing and releasing energy during the phase change process. Paraffin waxes and fatty acids have been applied as PCMs for thermal energy storage in solar heating and cooling applications due to their high storage density and small temperature variations from storage to retrieval. The use of paraffin is very common, and the maximum use frequency is up to 87.5% [1]. An effective method for enhancing thermal conductivity of PCMs and preventing possible interactions with the surrounding materials as well as leakage during the melting process is microencapsulating of phase change materials [2–4]. Microencapsulated phase change materials (MPCM) have drawn an increasing interest to provide enhanced thermal functionalities in a wide variety of applications such as medicine, biotechnology, food, agriculture, build- ings, pipelines, car interiors and thermal storage containers. An efficient energy management program must invariably involve energy storage in order to cater to fluctuations in demands and also obtain higher performance from the primary power plant [1–3]. PCMs with a melting point ranging from -10 to 80 °C can be used for microencapsulation [5]. The microencap- sulation technique depends upon the physical and chemical properties of the materials which are used. There are sev- eral physical and chemical methods that can be used for the production of microcapsules. The most important chemical technique used for the microencapsulation of PCMs is the in situ polymerization [6, 7], which includes interfacial [8], emulsion [9] and suspension polymerization methods [10, 11], although there are some other methods that can also be used [2, 12–17]. The in situ processes have the ability to yield & Nasrin Etesami netesami@cc.iut.ac.ir 1 Department of Chemical Engineering, Isfahan University of Technology, P.O. Box: 84156-83111, Isfahan, Iran 123 J Therm Anal Calorim DOI 10.1007/s10973-017-6516-9