Shape-stabilized poly(ethylene glycol) (PEG)-cellulose acetate blend preparation with superior PEG loading via microwave-assisted blending Swati Sundararajan, Asit B. Samui ⇑ , Prashant S. Kulkarni ⇑ Energy and Environment Laboratory, Department of Applied Chemistry, Defence Institute of Advanced Technology, Deemed University, Girinagar, Pune 411 025, India article info Article history: Received 18 May 2016 Received in revised form 16 November 2016 Accepted 28 December 2016 Keywords: Solid-solid phase change material Form-stable Microwave Poly(ethylene glycol) Cellulose acetate abstract Poly(ethylene glycol) (PEG) is known to be very effective phase change material (PCM), which has been processed by various techniques. Efforts for development of better processing technique are always on, to make the process product and performance superior. Microwave technology based process development for the preparation of form stable phase change composites was attempted, with the motivation of estab- lishing a green technique, which will be energy and time efficient and require minimum amount of sol- vent. The process could easily be scaled for large scale production of PCM blends. The microwave-assisted blending of PEG and cellulose acetate (CA) was carried out in various ratios resulting in the formation of biodegradable form-stable PCM. PEG acted as the latent heat storage material and cellulose acetate as the supporting material. As a result of microwave treatment, a high loading capacity of 96.5 wt% PEG was achieved without any leakage during the transition process. The blending was confirmed by Fourier- transform infrared spectroscopy (FTIR) analysis which showed no chemical bonds between PEG and CA. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) indicated that maxi- mum enthalpy of 155 J/g was attained and the material was found to have good thermal stability. The surface properties of these materials were studied by using contact angle for various weight percentages of PEG. The X-ray diffraction (XRD) investigation revealed that the crystallinity of the PEG-CA blend increased with increasing concentration of PEG. The morphology was studied with field-emission scan- ning electron microscopy (FESEM) and atomic force microscopy (AFM) suggesting a homogeneous net- work formation of the blend. Ó 2016 Elsevier Ltd. All rights reserved. 1. Introduction The depletion of non-renewable sources of energy coupled with escalating world demand for energy has gathered focus on the research for alternative sources of energy. Thermal energy storage systems can be used to address this global issue partially. Latent heat storage systems, also known as Phase Change Materials (PCMs) are gaining popularity due to their high energy storage density and ease of temperature control (Kenisarin, 2014; Samui et al., 2015). Solid-solid PCMs can be prepared by using both phys- ical methods (adsorption, blending, soaking) and chemical meth- ods (grafting, crosslinking, copolymerization) (Kumar et al., 2014). Various form-stable blends have been developed using inor- ganic hard segments but it leads to supercooling and phase separa- tion over repeated cycling (Qian et al., 2013). Therefore, organic form-stable blends offer better performance with good thermal efficiency. PEG is a versatile PCM with attractive properties such as high storage capacity per unit volume, ease of chemical modifi- cation, adjustable temperature range, non-toxicity, good chemical and thermal reliability (Alkan et al., 2012a; Qi et al., 2014; Samui et al., 2015; Sundararajan et al., 2016). Many shape-stabilized PCMs have been prepared using natural, biodegradable polymers such as cellulose (Liang et al., 1995; S ßentürk et al., 2011), cellulose acetate (Chen et al., 2007; Ding et al., 2001; Guo et al., 2003; Jiang et al., 2002), chitosan (S ßentürk et al., 2011), agarose (S ßentürk et al., 2011), sugars (Alkan et al., 2012b) and starch (Pielichowska and Pielichowski, 2010) as hard segments and PEG as the working material. Cellulose obtained from wood pulp was used to prepare PEG-cellulose blend using coagulation method with a maximum encapsulation of 40 wt% PEG (Liang et al., 1995). The crystalline to amorphous solid-solid phase transition was studied and melting enthalpy of 143 J/g was obtained. Guo et al. prepared PEG and CA physical blends by solu- tion casting up to maximum loading of 85% PEG and the phase http://dx.doi.org/10.1016/j.solener.2016.12.056 0038-092X/Ó 2016 Elsevier Ltd. All rights reserved. ⇑ Corresponding authors. E-mail addresses: absamui@gmail.com (A.B. Samui), ps_kulkarni@rediffmail.com (P.S. Kulkarni). Solar Energy 144 (2017) 32–39 Contents lists available at ScienceDirect Solar Energy journal homepage: www.elsevier.com/locate/solener