Fabrication of Thermal Intelligent Core/Shell Nanoﬁbers by the Solution Coaxial Electrospinning Process BABAK REZAEI, MOZHDEH GHANI, MOHSEN ASKARI, AHMAD MOUSAVI SHOUSHTARI, REZA MOHAMMAD ALI MALEK Department of Textile Engineering, AmirKabir University of Technology, Tehran 15875-4413, Iran Correspondence to: Ahmad Mousavi Shoushtari; e-mail: amousavi@aut.ac.ir. Received: December 1, 2014 Accepted: March 2, 2015 ABSTRACT: In this study, the authors present a promising structure of shape-stabilized phase change materials (PCMs) with remarkable thermal energy storage capacity as core/shell phase change nanoﬁbers. In this regard, solutions of polyethylene glycol (PEG) (as an important category of PCMs) and cellulose acetate (CA) were used as core and shell solutions, respectively. Electrospinning with a coaxial spinneret was performed, and nanoﬁbers with the mean diameter of 545 nm under the controlled condition were produced. The formation of the core/shell structure was veriﬁed by scanning electron microscopy, attenuated total reﬂection Fourier transform infrared spectroscopy, and transmission electron microscopy analyses. Moreover, thermogravimetric analysis results not only revealed the thermal stability improvement of PCM but also conﬁrmed the presence of the core/shell structure too. Differential scanning calorimetry analysis was also performed to measure the thermal energy storage capacity of the core/shell phase change nanoﬁbers before and after a thermal cyclic test. A major ﬁnding in the present study is that the thermal energy storage capacity of core/shell nanoﬁbers after the thermal cyclic test is signiﬁcantly higher (41.23 J/g) than initial one (14.77 J/g). Ultimately, it can be summarized that the special core/shell conﬁguration provides desirable thermal stability and durability concurrently along with high thermal energy storage capacity. C  2015 Wiley Periodicals, Inc. Adv Polym Technol 2015, 00, 21534; View this article online at wileyonlinelibrary.com. DOI 10.1002/adv.21534 KEY WORDS: Thermal properties, Nanostructured ﬁbers, Differential scanning calorimetry (DSC), Thermogravimetric analysis (TGA) Introduction W orld attention to the global warming in the recent decades is a solid proof for the importance of this issue. One of the most important factors in creating this phenomenon is greenhouse gases, which mostly are due to burning of the fos- sil fuels. 1,2 There are diverse solutions to prevent the growth of global warming, which are based on limiting the consumption of fossil fuels and may be classiﬁed in two broad categories: (1) the use of regenerable energy resources and (2) storage and reuse of the existing energy. 3 Thermal energy is one of the important existing types of energy that can be saved in the forms of sensi- ble, latent, and chemical reaction heat. 4 Phase change materials (PCMs) are able to store and retrieve a certain amount of ther- mal energy during a phase transition. 5 Because of high-energy storage density and small temperature variation from storage to retrieval, PCMs are worthy candidates to use in thermal energy storage systems and can play a determinative role in the future developments of these systems. 6 However, in spite of the above-mentioned desirable proper- ties, the direct use of these materials has been restricted due to some inherent disadvantages such as supercooling, low thermal conductivity, leaking in the liquid state, and being corrupted after several heating–cooling cycles. 7–9 Therefore, some mod- iﬁcation methods have been proposed, such as impregnation in porous materials, 9 micro- and nanoencapsulation, 8 and in- tegration in ﬁbrous structures 10,11 (the so-called “phase change ﬁbers”). In the latter case, PCMs will be imported into the ﬁbrous structures and will act as a thermal energy storage agent. 12 Ac- cording to the literature, it appears that the lower ﬁber diameters can rectify the low thermal conductivity of PCMs and improve the thermal permeability. 13 Thus, there are several reports that used the electrospinning process to produce phase change ul- traﬁne ﬁbers. 14–17 Electrospinning is a simple and efﬁcient tech- nique capable of generating ﬁbers with diameters in the range of micro to several nanometers from various polymers. 18,19 Based on the production process, an electrospinning tech- nique can be classiﬁed as ordinary and coaxial methods. 20 Com- posite phase change nanoﬁbers (CPCNs) would be formed by ordinary electrospinning of a PCM/polymer blend solution. 21 These CPCNs showed some attractive advantages, such as an improvement in the thermal permeability, ﬂexibility, thermal energy storage density, and increasing the surface to volume ratio. 22,23 Despite of the above-mentioned advantages, partially leaking and thermal decomposition for PCMs in the structure Advances in Polymer Technology, Vol. 00, No. 0, 2015, DOI 10.1002/adv.21534 C  2015 Wiley Periodicals, Inc. 21534 (1 of 8)