Thermal Energy Storage Properties Research Articles

Electrospun capric acid/polyethylene terephthalate composite nanofibres for storage and retrieval of thermal energy

Composite nanofibres based on capric acid (CA) and polyethylene terephthalate (PET) with different mass ratios of CA/PET ranging from 0·5∶1, 1∶1, 1·5∶1, 2∶1 to 2·5∶1 were fabricated by electrospinning as innovative form-stable phase change materials for storage and retrieval of thermal energy. The morphological structures, thermal energy storage properties and thermal stability of electrospun CA/PET composite nanofibres were characterised by field emission scanning electron microscopy (FE-SEM), transmission electronic microscopy (TEM), differential scanning calorimetry (DSC) and thermogravimetric analyses (TGA) respectively. The FE-SEM images revealed that the electrospun CA/PET composite nanofibres had a cylindrical morphology with average fibre diameters in the range of about 145–192 nm. Additionally, the FE-SEM and TEM images indicated that the CA distributed on the surface and within the core of the composite nanofibres. The results acquired from DSC analyses indicated that the mass ratio of CA versus PET played an important role on the enthalpy values of melting and crystallisation of the composite nanofibres, while it had no appreciable effect on the temperatures of phase transitions. Moreover, the results of DSC thermal cycling suggested that the thermal energy storage properties of the CA in the composite nanofibres had hardly been influenced during thermal cycling, indicating that the electrospun CA/PET composite nanofibres had good thermal reliability. The TGA results showed that both the onset thermal degradation temperature and the charred residue at 700°C of the composite nanofibres were lower than those of pure PET nanofibres as a result of the thermal instability of the CA molecular chains.

Complexing blends of polyacrylic acid-polyethylene glycol and poly(ethylene-co-acrylic acid)-polyethylene glycol as shape stabilized phase change materials

Blends of poly(ethylene glycol) (PEG) at 1000, 6000, and 10,000g/mole average molecular weights and poly(acrylic acid) (PAA) or poly(ethylene-co-acrylic acid) (EcoA) have been prepared by solution blending and accounted for thermal energy storage properties as shape stabilized polymer blends. The blends have been analyzed using Fourier transform infrared (FT-IR) spectroscopy and differential scanning calorimetry (DSC) techniques. Total thermal energy values of the complexes have been determined by the method of Mehling et al.As a result of the investigation it is found that polymers with acid groups form interpolymer complexes (IPCs) and miscible and immiscible IPC–PEG blends when blended with PEGs. PEGs formed IPCs with PAA and EcoA polymers in solutions and reach to saturation and turns to be blends of IPC and PEG polymer. PEGs in this work bleed out of the blends when its compositions reach to a degree of immiscibility. In the first range where blends are IPCs and in the third range where bleeding of PEG occurs, blends are not feasible for thermal energy storage applications. However, in the second range, the blends are potential materials for passive thermal energy storage applications.

Preparation, morphology and thermal properties of electrospun fatty acid eutectics/polyethylene terephthalate form-stable phase change ultrafine composite fibers for thermal energy storage

The ultrafine composite fibers based on the composites of binary fatty acid eutectics and polyethylene terephthalate (PET) with varied fatty acid eutectics/PET mass ratios (50/100, 70/100, 100/100 and 120/100) were fabricated using the technique of electrospinning as form-stable phase change materials (PCMs). The five binary fatty acid eutectics including LA–MA, LA–PA, MA–PA, MA–SA and PA–SA were prepared according to Schrader equation, and then were selected as an innovative type of solid–liquid PCMs. The results characterized by differential scanning calorimeter (DSC) indicated that the prepared binary fatty acid eutectics with low phase transition temperatures and high heat enthalpies for climatic requirements were more suitable for applications in building energy storage. The structural morphologies, thermal energy storage and thermal stability properties of the ultrafine composite fibers were investigated by scanning electron microscope (SEM), DSC and thermogravimetric analysis (TGA), respectively. SEM images revealed that the electrospun binary fatty acid eutectics/PET ultrafine composite fibers possessed the wrinkled surfaces morphologies compared with the neat PET fibers with cylindrical shape and smooth surfaces; the grooves or ridges on the corrugated surface of the ultrafine composite fibers became more and more prominent with increasing fatty acid eutectics amount in the composite fibers. The fibers with the low mass ratio maintained good structural morphologies while the quality became worse when the mass ratio is too high (more than 100/100). DSC measurements suggested that the heat enthalpies of melting and crystallization of the ultrafine composite fibers increased gradually with increasing fatty acid eutectics amounts, but their phase transition temperatures had almost no obvious variation as relative to the corresponding fatty acid eutectics. Meanwhile, the characteristic temperatures and heat enthalpies of the ultrafine composite fibers varied with the different types of binary fatty acid eutectics. TGA results indicated that the degradation of electrospun binary fatty acid eutectics/PET ultrafine composite fibers with representative mass ratio of 100/100 had two steps and corresponded respectively to the degradations of binary fatty acid eutectics and PET polymer chains; and the charred residue at 700°C of the composite fibers was lower than that of the neat PET fibers. It could be envisioned that the electrospun binary fatty acid eutectics/PET composite fibers would be extensively used for latent heat storage in the field of building energy conservation.

Thermal energy storage properties of mannitol–fatty acid esters as novel organic solid–liquid phase change materials

In this study, four kinds of mannitol–fatty acid esters were synthesized as novel organic phase change materials (PCMs) for thermal energy storage applications. The structural characterization of synthesized mannitol hexastearate (MHS), mannitol hexapalmitate (MHP), mannitol hexamyristate (MHM) and mannitol hexalaurate (MHL) were carried out using Fourier Transform Infrared (FT-IR), Proton Nuclear Magnetic Resonance (1H NMR), and 13C NMR spectroscopy methods. Thermal energy storage properties and thermal reliability of the synthesized PCMs were determined using differential scanning calorimetry (DSC) method at a heating rate of 1°C/min. DSC results showed that the melting temperatures of the PCMs were in the temperature range of 42–65°C and their latent heat values spanned between 145 and 202J/g. The latent heats of these PCMs are low compared to mannitol but they fall into the same range as fatty acids. The synthesized PCMs have much lower phase change temperatures and supercooling degree (about 1–8°C) and compared to the mannitol. They have also better odor, noncorrosivity and thermal durability properties as compared to the fatty acids. Thermal cycling test consisted of repeated 1000 melting/solidification cycles also revealed that the synthesized PCMs have good thermal reliability. In addition, thermal conductivity of the PCMs was increased significantly by addition of expanded graphite (EG) at 10wt%. Based on all results it can be concluded that the synthesized PCMs, MHS, MHP, MHM and MHL esters can be considered as promising solid–liquid PCMs for solar heating applications.

Preparation of halogen-free flame retardant hybrid paraffin composites as thermal energy storage materials by in-situ sol–gel process

Novel halogen-free flame retardant hybrid phase change composites were prepared by an in-situ sol–gel process, using paraffin as the thermal energy storage material and tri-(triethoxysilylpropyl) phosphamide as the sol–gel precursor. The structure of paraffin composites was characterized by Fourier transform infrared spectrum (FT-IR) and X-ray diffraction (XRD). The behaviors of thermal stability and thermal energy storage properties were investigated through thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The char residue of composites was characterized by FT-IR, XRD and scanning electron microscope (SEM). The flame retardancy property of paraffin composites was investigated by pyrolysis combustion flow calorimetry (PCFC). Results showed that the paraffin composites had good thermal energy storage property as well as enhanced thermal stability and flame retardancy properties.

Structural morphology and thermal performance of composite phase change materials consisting of capric acid series fatty acid eutectics and electrospun polyamide6 nanofibers for thermal energy storage

In this study, the capric acid (CA) was chosen and CA series fatty acid eutectics (e.g., capric acid–lauric acid, capric acid–palmitic acid, and capric acid–stearic acid) was prepared; thereafter, the composite phase change materials (PCMs) consisting of CA series fatty acid eutectics and electrospun polyamide 6 (PA6) nanofibers were prepared by physical absorption. The structural morphologies and thermal energy storage properties of the composite PCMs were characterized by SEM and DSC, respectively. The SEM results indicated that the CA series fatty acid eutectics confined into porous PA6 nanofiber membranes. The DSC results indicated that the phase transition temperatures of CA series fatty acid eutectics were lower than those of CA; the enthalpies of melting and crystallization of the composite PCMs were slightly decreased.

Thermal energy storage properties of paraffin and fatty acid binary systems

In this paper, 20 kinds of paraffin mixtures and fatty acid mixtures were prepared. Phase change temperatures of these mixtures are between 20°C and 30°C, and the phase change latent heats are big. The phase change temperatures and latent heats of these materials were tested by differential scanning calorimeter after multiple heat cycles. The testing results were compared in order to discuss the thermal stabilities of paraffin mixtures and fatty acid mixtures. The results showed that the thermal stabilities of phase change materials (PCMs) are good after 500 cycles, and the phase change temperatures and latent heats have small fluctuations. The thermal stability of fatty acids mixtures is better than that of paraffin materials. Paraffin mixtures and fatty acid mixtures are ideal PCMs used for the wall because of their good stabilities. The results can provide reference and basis for the application of paraffin and fatty acid in the energy-saving.

Synthesis and thermal properties of poly(styrene-co-ally alcohol)-graft-stearic acid copolymers as novel solid–solid PCMs for thermal energy storage

A series of poly(styrene-co-allyalcohol)-graft-stearic acid copolymers were synthesized as novel polymeric solid–solid phase change materials (SSPCMs). The graft copolymerization reactions between poly(styrene-co-allyalcohol) and stearoyl chloride were verified by Fourier transform infrared (FT-IR) and Proton Nuclear Magnetic Resonance (1H NMR) spectroscopy techniques. The crystal morphology of the SSPCMs was investigated using polarized optical microscopy (POM) technique. Thermal energy storage properties of the synthesized SSPCMs were measured using differential scanning calorimetry (DSC) analysis. The POM results showed that the crystalline phase of the copolymers transformed to amorphous phase above their phase transition temperatures. Thermal energy storage properties of the synthesized SSPCMs were investigated by differential scanning calorimetry (DSC) and found that they had typical solid–solid phase transition temperatures in the range of 27–30°C and high latent heat enthalpy between 34 and 74J/g. Especially, the copolymer with the mole ratio of 1/1 (poly(styrene-co-allyalcohol)/stearoyl chloride) is the most attractive one due to the highest latent heat storage capacity among them. The results of DSC and FT-IR analysis indicated that the synthesized SSPCMs had good thermal reliability and chemical stability after 5000 thermal cycles. Thermogravimetric (TG) analysis results suggested that the synthesized SSPCMs had high thermal resistance. In addition, thermal conductivity measurements signified that the synthesized PCMs had higher thermal conductivity compared to that of poly(styrene-co-allyalcohol). The synthesized copolymers as novel SSPCMs have considerable potential for thermal energy storage applications such as solar space heating and cooling in buildings and greenhouses.

Treatment of natural stones with Phase Change Materials: Experiments and computational approaches

The treatment of natural stones with Phase Change Materials (PCMs) is experimentally and computationally investigated with respect to developing innovative products with thermal energy storage properties. The objective is to improve the thermal properties of natural stone by exploiting associated latent heat storage phenomena. As a consequence, natural stone treated with PCMs could be used as a construction material with the ability to store thermal energy leading to reduction of the overall buildings' energy consumption. In order to demonstrate the effectiveness of this concept, a series of experiments has been performed. At first, measurements were focused on the PCM influence at the natural stone thermal properties at sample scale. At product scale, a number of “model” concrete pilot houses have been constructed. The pilot houses were covered with trans-ventilated façade design using the Spanish “Bateig azul” natural stone. Two cases have been examined, with and without PCM integrated in the natural stone façade. Variations of indoor temperatures have been monitored for several day–night cycles showing that a smoother indoor temperature profile is obtained when PCMs are implemented. An improvement in human comfort and a reduction of energy consumption can thus be anticipated. Furthermore, a composite computational model based on the linking of TRNSYS platform to a MATLAB subroutine is introduced. The performance of the tool is evaluated with respect to the aforementioned measurements. It is shown that a good agreement between computational results and experimental data can be achieved. Parametric studies focused on the PCM influence, highlighting the advantages of the combined experimental and computational approaches.

Electrospun ultrafine composite fibers consisting of lauric acid and polyamide 6 as form-stable phase change materials for storage and retrieval of solar thermal energy

The ultrafine composite fibers consisting of lauric acid (LA) and polyamide 6 (PA6) with varied LA/PA6 mass ratios of 80/100, 100/100, 120/100, and 150/100 were prepared via the technique of electrospinning as form-stable phase change materials (PCMs); morphological structures of the fibers were characterized, and their thermal stability and thermal energy storage properties were investigated. SEM results indicated that electrospun LA/PA6 composite fibers possessed the ribbon-shaped morphology with fiber diameters slightly larger than those of the neat PA6 fibers. The study revealed that the LA primarily existed as phase separated domains and the domains were randomly dispersed in as-electrospun ultrafine composite fibers. To reveal the evolution of morphological structures and the resulting properties for storage and retrieval of thermal energy, the heat treatment at 60°C for the electrospun composite fibers with LA/PA6 mass ratio of 100/100 was carried out; upon the heat treatment, the complete encapsulation of LA domains inside PA6 matrices would occur, and the heat-treated fibers might even possess the partial core/sheath structure with LA being the core and PA6 being the sheath. TGA results indicated that the degradation of electrospun LA/PA6 ultrafine composite fibers had two steps, and the charred residue at 700°C of the composite fibers was lower than that of the neat PA6 fibers. DSC measurements suggested that the amount of LA in the fibers played an important role on the values of heat enthalpies for the composite fibers; while it had no appreciable effect on the temperatures of phase transitions. After the heat treatment, the values of heat enthalpies for the composite fibers decreased slightly and this was due to the complete encapsulation of LA and/or the confinement effect of PA6 matrix, both of which constrained the movement of LA molecules. It is envisioned that the electrospun ultrafine composite fibers with PCMs (e.g., fatty acids) encapsulated in the supporting polymeric matrices (e.g., PA6) would be innovative form-stable PCMs for storage and retrieval of solar thermal energy.

Synthesis and thermal energy storage properties of the polyurethane solid–solid phase change materials with a novel tetrahydroxy compound

Based on the phase change theory, a novel tetrahydroxy compound (THCD) was designed and prepared. Depending on the spatial structure of the tetrahydroxy compound, a form-stable thermoplastic polyurethane solid–solid phase change material (TPUPCM) was synthesized via employing PEG as soft segments, while multi-benzene ring structure made by 4,4′-diphenylmethane diisocyanate and tetrahydroxy compound as hard segments. The composition and structure of THCD and TPUPCM, the TPUPCM’s the weight average molecular weight and number average molecular weight, dissolving and melting abilities, phase change behaviors, thermal performances and crystalline morphology were investigated by Fourier transform infrared spectrometer, 1H nuclear magnetic resonance spectrometer, multiangle laser light scattering apparatus, differential scanning calorimentry, dynamic mechanical thermal analysis, thermogravimetry analysis system, wide-angle X-ray diffraction, polarizing optical microscopy. The results show that the solid–solid phase change material owns excellent phase change properties and a broad processing temperature range. The heating cycle phase change enthalpy is 137.4J/g, and the cooling cycle phase change enthalpy is 127.6J/g. The started decomposition temperature and the maximum decomposition temperature are at 323.5 and 396.2°C, respectively. Furthermore, the solid–solid phase change material is dissolvable, meltable and can be processed directly, and has great potential applications in thermal energy storage.

Preparation and thermal energy storage properties of building material-based composites as novel form-stable PCMs

In this study, ten kinds of composite phase change materials (PCMs) were prepared by impregnation of xylitol penta palmitate (XPP) and xylitol penta stearate (XPS) esters into gypsum, cement, diatomite, perlite and vermiculite via vacuum adsorption method. The form-stable composite PCMs were characterized by using SEM and FT-IR, DSC and TG analysis techniques. The maximum impregnation ratio of both XPP and XPS into gypsum, cement, perlite, diatomite, and vermiculite were found to be 22, 17, 67, 48 and 42wt%, respectively. The DSC results showed that the melting temperatures and latent heat capacities of the composite PCMs varied from 20°C to 35°C and from 38J/g to 126J/g. TG investigations revealed that the composite PCMs had excellent thermal durability above their working temperature ranges. The thermal cycling test also exhibited that the composite PCMs had good thermal reliability and chemical stability. In addition, thermal conductivities of the composite PCMs were increased by addition of EG in mass fraction of 10%. All of the conclusions indicated that among the prepared composite PCMs, especially perlite and diatomite based-PCMs are potential candidates for energy storage applications such as solar heating and cooling in buildings since they had relatively higher latent heat capacity.

Polyurethanes as solid–solid phase change materials for thermal energy storage

Polyurethane polymers (PUs) have been synthesized as solid–solid phase change materials for thermal energy storage using three different kinds of diisocyanate molecules and polyethylene glycols (PEGs) at three different molecular weights. PEGs and their derivatives are usually used as phase change units in polymeric solid–solid phase change materials due to the hydroxyl functional groups. 1000, 6000, and 10,000g/mol number average molecular weight PEGs are used as working element as hexamethylene, isophorone, and toluene diisocyanates are used as hard segment at the backbone. The effects of molecular weight of PEG and type of diisocyanate on the thermal energy storage properties have been discussed. Only two of the produced polymers show solid–liquid phase change as the rest show solid–solid phase transitions. The produced PUs with a solid–solid phase transitions have potential to be used in thermal energy storage systems.

Poly(2‐alkyloyloxyethylacrylate) and poly(2‐alkyloyloxyethylacrylate‐co‐methylacrylate) comblike polymers as novel phase‐change materials for thermal energy storage

AbstractA series of poly(2‐alkyloyloxyethylacrylate) and poly(2‐alkyloyloxyethylacrylate‐co‐methylacrylate) polymers as novel polymeric phase‐change materials (PCMs) were synthesized starting from 2‐hydroxyethylacrylate and fatty acids. The chemical structure and crystalline morphology of the synthesized copolymers were characterized with Fourier transform infrared and 1H‐NMR spectroscopy and polarized optical microscopy, respectively, and their thermal energy storage properties and thermal stability were investigated with differential scanning calorimetry and thermogravimetric analysis, respectively. The thermal conductivities of the PCMs were also measured with a thermal property analyzer. Moreover, thermal cycling testing showed that the copolymers had good thermal reliability and chemical stability after they were subjected to 1000 heating/cooling cycles. The synthesized poly(2‐alkyloyloxyethylacrylate) polymers and poly(2‐alkyloyloxyethylacrylate‐co‐methylacrylate) copolymers as novel PCMs have considerable potential for thermal energy storage and temperature‐control applications. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Synthesis and thermal energy storage properties of xylitol pentastearate and xylitol pentapalmitate as novel solid–liquid PCMs

In this study, xylitol pentastearate and xylitol pentapalmitate were synthesized as novel solid–liquid PCMs by an esterification reaction in order to eliminate the unfavorable thermal properties of xylitol (such as high melting point) and stearic and palmitic acids (such as high melting point, low corrosivity, bad odor, and sublimating property). The synthesized ester compounds were characterized chemically by using Fourier transform infrared (FT-IR) and proton nuclear magnetic resonance (1H NMR) spectroscopy methods. By using the differential scanning calorimetry (DSC) method, the melting temperatures of xylitol pentastearate and xylitol pentapalmitate were measured as 32.35°C and 18.75°C, respectively, while their latent heats of melting were determined as 205.65Jg−1 and 170.05Jg−1 respectively. These results indicate that the synthesized PCMs have high latent heat values and suitable phase change temperatures for thermal energy storage applications. The thermal cycling test shows that the synthesized PCMs have good thermal reliability after 1000 thermal cycles. Thermogravimetric (TG) analysis results also reveal that the PCMs have good thermal stability over their working temperatures.

Thermal energy storage properties and thermal reliability of some fatty acid esters/building material composites as novel form-stable PCMs

In this study, thermal energy storage properties and thermal reliability some fatty acid esters/building material composites as novel form-stable phase change materials (PCMs) were investigated. The form-stable composite PCMs were prepared by absorbing galactitol hexa myristate (GHM) and galactitol hexa laurate (GHL) esters into porous networks of diatomite, perlite and vermiculite. In composite PCMs, fatty acid esters were used as energy storage materials while diatomite, perlite and vermiculite were used as building materials. The prepared composite PCMs were characterized using scanning electron microscope (SEM) and Fourier transformation infrared (FT-IR) analysis techniques. The SEM results proved that the esters were well confined into the building materials. The maximum mass percentages of GHM adsorbed by perlite, diatomite and vermiculite were determined as 67, 55 and 52wt%, respectively as they were found for GHL to be 70, 51 and 39wt%, respectively. Thermal properties and thermal stabilities of the form-stable composite PCMs were determined using differential scanning calorimetry (DSC) analysis. The DSC results showed that the melting temperatures and latent heat values of the PCMs are in range of about 39–46°C and 61–121J/g. The thermal cycling test revealed that the composite PCMs have good thermal reliability and chemical stability. TG analysis revealed that the composite PCMs had high thermal durability property above their working temperature ranges. Moreover, the thermal conductivities of the PCMs were increased by adding the expanded graphite (EG) in mass fraction of 5%. Based on all results, it was also concluded that the prepared six composite PCMs had important potential for thermal energy storage applications such as solar space heating and cooling applications in buildings.

Thermal energy storage by poly(styrene‐co‐p‐stearoylstyrene) copolymers produced by the modification of polystyrene

AbstractA series of poly(styrene‐co‐p‐stearoyl styrene) copolymers as novel polymeric solid–solid phase‐change materials (SSPCMs) were synthesized by the modification of polystyrene with stearoyl chloride. The chemical structure and crystalline morphology of the synthesized copolymers were determined with Fourier transform infrared spectroscopy and polarized optical microscopy, respectively. The thermal energy storage properties and thermal stability of the SSPCMs were investigated with differential scanning calorimetry and thermogravimetric analysis, respectively. In addition, the thermal conductivity of the SSPCMs was measured with a thermal property analyzer. Moreover, thermal cycling tests showed that the copolymers had good thermal reliability and chemical stability after being subjected to 5000 heating/cooling cycles. The synthesized poly(styrene‐co‐stearoyl styrene) copolymers as novel SSPCMs have considerable potential for thermal energy storage and temperature‐control applications. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Electrospun ultrafine composite fibers of binary fatty acid eutectics and polyethylene terephthalate as innovative form-stable phase change materials for storage and retrieval of thermal energy

SUMMARY In this study, four fatty acids of lauric acid (LA), myristic acid (MA), palmitic acid (PA), and stearic acid (SA) were selected to prepare six binary fatty acid eutectics of LA-MA, LA-PA, LA-SA, MA-PA, MA-SA, and PA-SA; thereafter, electrospun ultrafine composite fibers with the binary fatty acid eutectics encapsulated in the supporting matrices of polyethylene terephthalate (PET) were prepared as innovative form-stable phase change materials for storage and retrieval of thermal energy. The morphological structures and thermal energy storage properties of the ultrafine composite fibers were characterized by scanning electron microscope (SEM) and differential scanning calorimeter (DSC), respectively. The SEM results indicated that the fibers had the cylindrical morphology with diameters of 1–2 µm; some had smooth surfaces, while others had wrinkled surfaces with grooves. The DSC results indicated that the phase transition temperatures of binary fatty acid eutectics were lower than those of individual fatty acids; the enthalpy values associated with melting and crystallization for the eutectics encapsulated in the composite fibers were considerably reduced, whereas there were no appreciable changes on the phase transition temperatures. Copyright © 2012 John Wiley & Sons, Ltd.

Influences of gamma irradiation on structure, thermal stability and thermal energy storage properties of form stable phase change materials

AbstractForm stable phase change materials (PCMs) were prepared from high density polyethylene (HDPE), poly(ethylene-co-vinyl acetate) (EVA), organophilic montmorillonite (OMT) and paraffin. The influences of gamma irradiation on the structure, thermal stability and thermal energy storage properties of form stable PCMs were studied by X-ray diffraction (XRD), scanning electronic microscopy (SEM), thermogravimetry analysis (TGA) and differential scanning calorimeter (DSC). The XRD results indicated that the morphological structure of intercalation for form stable PCMs would not be appreciably varied by gamma irradiation. The SEM images showed that the intermolecular cross-linking induced by gamma irradiation made the three-dimensional network structure more compact and the interface more illegible. The results of TGA analyses indicated that the thermal stability of form stable PCMs after gamma irradiation was higher than that of the corresponding PCMs before gamma irradiation, and the enhancement slightly ...

Synthesis and thermal properties of polystyrene-graft-PEG copolymers as new kinds of solid–solid phase change materials for thermal energy storage

A series of polystyrene-graft-PEG6000 copolymers were synthesized as new kinds of polymeric solid–solid phase change materials (SSPCMs). The synthesized SSPCMs storage latent heat as the soft segments PEG6000 of the copolymers transform from crystalline phase to amorphous phase and therefore they can keep its solid state during the phase transition processing. The graft copolymerization reaction between polystyrene and PEG was verified by Fourier transform infrared (FT-IR) and 1H NMR spectroscopy techniques. The morphology of the synthesized SSPCMs was characterized by polarization optical microscopy (POM). Thermal energy storage properties, thermal reliability and thermal stability of the synthesized SSPCMs were investigated by differential scanning calorimetry (DSC) and thermogravimetric (TG) analysis methods. The DSC results showed that the synthesized SSPCMs had typical solid–solid phase transition temperatures in the range of 55–58°C and high latent heat enthalpy in the range of 116–174Jg−1. The TG analysis findings showed that the synthesized SSPCMs had high thermal durability above their working temperatures. Also, thermal conductivity measurements indicated that the synthesized PCMs had higher thermal conductivity compared to that of polystyrene. The synthesized polystyrene-graft-PEG6000 copolymers as new kinds of SSPCMs could be used for thermal energy storage.