On the thermal performance of a novel PCM nanocapsule: The effect of core/shell Hediyeh Nikpourian a , Ahmad Reza Bahramian a, * , Mahdi Abdollahi b a Polymer Engineering Department, Faculty of Chemical Engineering, Tarbiat Modares University, P.O.Box 14115-143, Tehran, Iran b Polymer Reaction Engineering Department, Faculty of Chemical Engineering, Tarbiat Modares University, P.O.Box 14115-143, Tehran, Iran article info Article history: Received 29 April 2019 Received in revised form 15 October 2019 Accepted 8 November 2019 Available online xxx Keywords: Nanoencapsulation Phase change materials Interfacial polymerization Polyurethane Thermal properties Semi solvent-non solvent method abstract To control the particle size distribution of nanocapsules, the nanoencapsulation of paraffin wax with polyurethane (PU) is performed via the interfacial polymerization. For this purpose, the spherical and solid nanoparticles of paraffin wax are first prepared using the novel semi solvent-non solvent method in the presence of sodium dodecyl sulfate (SDS). Then, the obtained nanoparticles are encapsulated with a polyurethane shell, based on novolac and toluene 2,4-diisocyanate (TDI). The chemical structure, thermal performance, microstructure and morphology of nanocapsules are investigated. The FESEM results confirm the formation of spherical paraffin wax nanoparticles with a particle size distribution of 25 e185 nm. The effect of core/shell mass ratio on the thermal properties of the obtained nanocapsules was studied. According to DSC results, the energy storage efficiency and the energy storage capacity of adequate nanocapsules are 80.2% and 97.5%, respectively. The successful nanoencapsulation of paraffin wax with a polyurethane-based shell is confirmed by TEM analysis. Moreover, the thermal cycling tests indicate the high thermal resistance of prepared core-shell system, even after 100 heating/cooling cycles, and have an excellent potential for energy storage and release performance of the system. © 2019 Elsevier Ltd. All rights reserved. 1. Introduction Phase change materials (PCMs) belong to the family of latent heat storage materials. They can absorb and release thermal en- ergy due to their phase change enthalpy during the melting and crystallization phase transition process [1 ,2]. High thermal sta- bility, high density, small volume changes during phase transition and high latent heat of fusion are the main thermodynamic properties of PCMs for being useable in practical applications [3,4]. PCMs based on paraffins are commonly used as the core material of micro and nanocapsules due to their appropriate melting/crystallization temperature, high energy storage capacity, good thermal reliability, fast crystallization process and being easy to encapsulate [5,6]. Despite having low thermal conduc- tivity of paraffins, there are several methods to enhance the thermal conductivity of this materials, such as dispersing highly conductive nano-sized particles and addition of different matrix structures into the PCM. But their challenges are the preparation process, a dramatic increase in viscosity, and a reduction in latent heat capacity of PCM [7 ,8]. A variety of techniques have been offered to enhance the heat transfer performance of the fluids [9]. A large number of researches have been investigated to increase the thermal conductivity of base fluids by suspending micro or nano-sized particles in the fluids, which they are called micro or nanofluids [10, 11]. Many different solid particles such as PCMs have been used in the fluids to form slurries. This process can be significantly increased the heat transfer rate and the effective thermal conductivity of the fluids in comparison with pure liquids [12, 13]. The encapsulation of PCMs is a promising solution to the leakage issue of organic PCMs [14]. Using this method, not only any reaction between PCMs and the environment can be prevented, but also supercooling and the leakage amount of the PCM during the phase transition can also be reduced [15]. In this technique, fabrication of capsules with the highest possible mass percentage of the PCM in the structure and the highest encapsulation efficiency are main goals [16e18]. Due to the high chemical stability and good me- chanical strength of organic shells, extensive efforts have been mounted for decades to develop the concept of PCM encapsulation with different organic shells such as melamine-formaldehyde (MF) [19], urea-formaldehyde (UF) [20], polymethylmethacrylate * Corresponding author. E-mail address: abahramian@modares.ac.ir (A.R. Bahramian). Contents lists available at ScienceDirect Renewable Energy journal homepage: www.elsevier.com/locate/renene https://doi.org/10.1016/j.renene.2019.11.027 0960-1481/© 2019 Elsevier Ltd. All rights reserved. Renewable Energy xxx (xxxx) xxx Please cite this article as: H. Nikpourian et al., On the thermal performance of a novel PCM nanocapsule: The effect of core/shell, Renewable Energy, https://doi.org/10.1016/j.renene.2019.11.027