Phase Change Materials Microcapsules Research Articles

Preparation of PMMA/SiO2 PCM microcapsules and its thermal regulation performance on denim fabric

PurposeThis study aims to evaluate the thermal performance of phase change materials (PCMs) microcapsules (MCs) attached using SiO2 microspheres and investigate the thermal regulation effect on the coated denim fabric.Design/methodology/approachThe PCM microcapsule was prepared by in situ polymerization using a mixture of solid paraffin and butyl stearate as core material (CM) and methyl methacrylate as a monomer. The SiO2 microparticles were attached to the outer layer of the membrane to enhance the thermal performance of MCs. The morphology, chemical structure, latent heat storage and thermal resistance of MCs were characterized. PCM MCs were coated on the denim fabric and thermo-gravimetric analysis was conducted; thermal insulation and thermal infrared imaging performance of the coated fabrics were also investigated.FindingsThe diameters of SiO2 particles and PCMs MCs were 300-500 nm and 1 μm, respectively. SiO2 was wrapped on single-wall PCMs MCs with the mass ratio of 1:5. With the addition of SiO2, the phase transition temperature range of MCs increased from 34°C to 39°C, and the endothermic and exothermic latent heat decreased by 5.35 J/g and 10.07 J/g, respectively. The degradation rate of MCs was significantly slowed down at high temperature. The denim fabric coated with MCs revealed thermal regulation property. After absorbing heat, the MCs slowed down the rate of heat loss and extended the heat release time.Research limitations/implicationsThe phase transition temperature of the composite CM was wide, and the latent heat storage was reduced. The addition of SiO2 particles can significantly slow down the rate of heat loss, but it further reduces the latent heat storage performance.Practical implicationsThe method developed provided a simple and practical solution to improve the thermal regulation performance of fabrics.Originality/valueThe method of adjusting the phase transition temperature range of the composite CM is novel and many applications could be found in preparation of PCMs and thermal management.

Thermo-regulating properties of textiles with incorporated microencapsulated Phase Change Materials

Phase change materials (PCMs) are getting increasing interest due to their capacity to absorb, store and release heat energy. Their effectiveness is characterized by quantities of absorbed/released heat energy, expressed as enthalpy. Specifically, the larger is the enthalpy, the more efficient thermoregulation effect is achieved. With this in mind, PCMs can be used in the manufacture of thermally regulated clothing in order to minimize heat strain and simultaneously improve thermal comfort. Moreover, such materials also modify their infrared radiation emission during phase transition, thus they can be envisioned to exploit thermal shielding applications. The aim of the present research was to investigate the infrared emissivity of textiles composed by cotton yarns with dispersed PCMs. The organic microcapsules of phase change materials, having different binding to the fibre mechanisms, were padded onto the fabric surface by pad-dry-cure method. The thermal properties and stabilities were measured using differential scanning calorimetry, while infrared emissivity was characterized using infrared thermographic technique. The obtained experimental results show a dynamic tuning of IR emissivity during heating/cooling process which can be correlated to the type and properties (enthalpy of fusion) of the corresponding PCM.

Detailed experimental and theoretical investigation of the thermomechanical properties of epoxy composites containing paraffin microcapsules for thermal management

AbstractMicroencapsulated phase change materials (PCMs) are being increasingly employed as functional fillers in polymer matrices for thermal management. Therefore, the effect of PCM microcapsules on the rheological, microstructural, thermal and mechanical properties of the host polymer matrices must be understood. This work concerned the preparation of epoxy polymers filled with PCM microcapsules (MC) in various concentrations and their subsequent characterization. The MC phase increases the viscosity of epoxy before curing, thereby reducing castability and hindering elimination of air bubbles. The latter was reflected in an increase in porosity for highly filled compositions, as elucidated by density measurements and microscopic investigation. SEM micrographs showed that the adhesion between the capsule shell and the epoxy matrix was not optimal. The interfacial weakness and the intrinsic low stiffness and strength of MC caused a reduction in mechanical properties, as evidenced by the Nicolais‐Narkis and Pukanszky models. On the other hand, at zero or low deformation levels, the interface presents no gaps and is able to transfer load and heat, as demonstrated by the data of elastic modulus, modeled with the Halpin‐Tsai and Lewis‐Nielsen models, and those of thermal conductivity, in excellent agreement with the Pal model. POLYM. ENG. SCI., 2020. © 2020 Society of Plastics Engineers

Preparation and characterization of carbon nanotube microcapsule phase change materials for improving thermal comfort level of buildings

The phase change material (PCM) microcapsule is a common high-performance storage technology of thermal energy. However, the organic wall with low thermal conductivity for PCM reduces the efficiency of heat storage and release. In this study, the novel carbon nanotube-doped phase change materials (C-PCMs) were developed. Scanning electron microscope test (SEM), Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC) and the thermogravimetric analysis/infrared spectrometry (TG-IR) were used to analyse the composite structure and thermal performances. The results indicate that C-PCMs are small and regular in spherical shape. When C-PCMs suffer from heat, the shell can maintain integrity below 165 °C. Furthermore, the carbon nanotubes in the shell play as a channel to connect the inside with the outside and improve the efficiency of heat transfer. The DCS test of the samples showed that the latent heat of C-PCMs and PCMs were 112.25 J/g and 116.18 J/g, respectively. The initial phase transition temperature of C-PCMs is 28.97 °C, which is 0.5 °C lower than that of PCMs. The results of the model room test suggested that the composite filled with C-PCMs reduces indoor temperature fluctuations and exhibits the potential for enhancing energy savings and the thermal comfort of buildings.

Preservation of traditional Chinese pork balls supplemented with essential oil microemulsion in a phase-change material package.

In this study, we evaluated the combined effect of cinnamon essential oil (CEO) microemulsions, and a temperature buffering package using phase-change material (PCM) microcapsules on the physicochemical property, lipid oxidation, and bacterial load of traditional Chinese pork balls (shi zi tou) during temperature fluctuation storage for 9 days. Transmission electron microscope characterization revealed that n-tetradecane microcapsules possessed a core-shell spherical shape with a size ranging from 300 to 600 nm. The use of n-tetradecane microcapsule packaging was found to maintain cold storage temperature efficiently. After 9 days of storage, the combination of CEO microemulsions with n-tetradecane microcapsules did not lead to changes in the color parameters of pork balls. At day 9, n-tetradecane microcapsules, used alone or in combination with CEO microemulsions, showed lower thiobarbituric acid reactive substances (TBARS) values than the control group, while their combination exhibited the lowest pH and 1,1-diphenyl-2-picrylhydrazyl (DPPH) values. Furthermore, the combination treatment retarded the growth of total plate count, lactic acid bacteria, Enterobacteriaceae, and Staphylococcus spp. after 4 and 9 days. The combinations of CEO microemulsions and PCM microcapsules could extend the shelf-life of cooked pork products, suggesting a feasible strategy for meat preservation. © 2020 Society of Chemical Industry.

Phase Change Material (PCM) Microcapsules for Thermal Energy Storage

Phase change materials (PCMs) are gaining increasing attention and becoming popular in the thermal energy storage field. Microcapsules enhance thermal and mechanical performance of PCMs used in thermal energy storage by increasing the heat transfer area and preventing the leakage of melting materials. Nowadays, a large number of studies about PCM microcapsules have been published to elaborate their benefits in energy systems. In this paper, a comprehensive review has been carried out on PCM microcapsules for thermal energy storage. Five aspects have been discussed in this review: classification of PCMs, encapsulation shell materials, microencapsulation techniques, PCM microcapsules’ characterizations, and thermal applications. This review aims to help the researchers from various fields better understand PCM microcapsules and provide critical guidance for utilizing this technology for future thermal energy storage.

Assessment of Thermal Performance of Textile Materials Modified with PCM Microcapsules Using Combination of DSC and Infrared Thermography Methods.

The aim of the study was the combination of two measurement methods, the differential scanning calorimetry (DSC) and infrared thermography to evaluate thermal performance of woven and knitted fabrics coated with acrylic pastes containing 20% (P/20) and 40% (P/40) of microcapsules of phase change materials (MPCM) with transition temperatures of 28 °C (MPCM28) and 43 °C (MPCM43). The DSC analysis showed that the phase transition processes for materials modified with pastes P/20 occur in a narrower temperature range than those modified with P/40 pastes. The initial temperatures TOnset (S-S) and TOnset (S-L) are higher for materials modified respectively with pastes P/20 and P/40. The melting and crystallization enthalpy values of both P/20 coated materials are lower by about 45% and 35% compared to P/40. Infrared thermography analysis showed that materials modified with P/20 are heating up faster than modified with P/40 for both MPCM. In the cooling process for modified fabrics the highest temperature decrease was observed in the first 30s. Materials modified with paste P/40 were cooled more slowly in comparison with paste P/20, both for MPCM28 and MPCM43.

A Novel Polymeric Adsorbent Embedded with Phase Change Materials (PCMs) Microcapsules: Synthesis and Application.

The heat released during the industrial gas adsorption (e.g., volatile organic compounds (VOCs)) on adsorbents (e.g., activated carbon) would lead to the risks of fire and explosion in the adsorption column. Herein, a novel highly-porous Vinylbenzyl chloride-Divinylbenzene (VBC-DVB) polymeric adsorbent was synthesized with embedded microcapsules (Hypercrosslinked VBC-DVB Beads (HVPM)). These microcapsules have a polydivinylbenzene-phase change materials (DVB-PCMs) core-shell structure. Paraffin wax was used as PCM filling in the spherical capsule. This microcapsules-embedded polymeric adsorbent HVPM (Φ1.5–2.0 mm) is found to possess a high specific surface area (~665 m²/g) and micropore-dominant structure. It also has heat storage capability indicated by DSC (Differential Scanning Calorimetry) analysis (11.1 J/g heat of fusion between 35.0 and 48.2 °C) for the encapsulated paraffin wax. The lab adsorption tests proved the capabilities of HVPM in adsorbing VOCs (toluene, 0.21 g/g) and controlling the temperature inside the adsorption column during the dynamic adsorption process, in which the temperature rise was lowered by 62.5%, relatively.

Performance of metal and non-metal coated phase change materials microcapsules when used in compressed air energy storage system

Using phase change material microcapsules (PCMCs) in direct contact with a compressed air in an adiabatic compressed air energy storage system (ACAES) is an effective approach to capture the heat generated during air compression and to recover it later during decompression. In this work, three different PCMCs were investigated, including those coated with metal. The PCMCs were placed inside air-storage cylinder and compressed to 200 bar. The PCMCs stability against air compression/decompression after 20x cycles was investigated using particle size distribution analyser (PSD), differential scanning calorimeter (DSC) and scanning electron microscope (SEM). The Micronal PCMCs show better thermal storing/releasing performance than other microcapsules showing no significant changes in its thermal behaviour after 20 cycles. In terms particle size distribution, Micronal 5038X and metal-coated Microtek24D MPCMCs retained their sizes after 20 cycles. From the DSC analysis, Micronal capsules show minor reduction in heat storage capacity after 20 cycle and retained good morphology based on SEM photo.

Synthesis and performance evaluation of paraffin microcapsules with calcium carbonate shell modulated by different anionic surfactants for thermal energy storage

A series of phase change materials (PCMs) microcapsules based on industrial paraffin core and calcium carbonate (CaCO3) shell were successfully synthesized for thermal energy storage. The SEM results revealed that the composites are mainly of spherical morphology. The FT-IR and XRD confirmed that the composites were mainly composed of the vaterite CaCO3, paraffin, and a small amount of calcite CaCO3. Compared with the composites prepared with sodium dodecyl sulfonate (SDS) as anionic surfactant, DSC and TG results of composites prepared with sodium dodecyl benzene sulfonate (SDBS) demonstrated that the encapsulation efficiency increased but the thermal stability decreased. Besides, with the different concentrations of CaCl2, the influence of anionic surfactants on the performance of microcapsules had been discussed. The results exhibited higher encapsulation efficiency of microcapsules with SDBS than that with SDS, even up to ten times. When the mass of CaCl2 is about 0.05 mol, encapsulation efficiency with SDBS can reach up to 20.80%. Accordingly, the super-cooling of PCM was significantly suppressed. From all results, it is worth developing the PCMs microcapsules with CaCO3 shell modulated by different anionic surfactants for thermal energy storage and SDBS is more suitable for preparing PCM@CaCO3 microcapsules.

Erratum for “Preparation of Low-Temperature Phase Change Materials Microcapsules and Its Application to Asphalt Pavement” by Feng Li, Siqi Zhou, Sai Chen, Zhenglong Yang, Jian Yang, Xingyi Zhu, Yuchuan Du, Peiting Zhou, and Zhihao Cheng

Erratum for “Preparation of Low-Temperature Phase Change Materials Microcapsules and Its Application to Asphalt Pavement” by Feng Li, Siqi Zhou, Sai Chen, Zhenglong Yang, Jian Yang, Xingyi Zhu, Yuchuan Du, Peiting Zhou, and Zhihao Cheng

Mechanical Strength Enhancement of Polylactic Acid Hybrid Composites.

In recent years, there has been an increasing need for materials that are environmentally friendly and have functional properties. Polylactic acid (PLA) is a biomass-based polymer, which has attracted research attention as an eco-friendly material. Various studies have been conducted on functionality imparting and performance improvement to extend the field of application of PLA. Particularly, research on natural fiber-reinforced composites have been conducted to simultaneously improve their environmental friendliness and mechanical strength. Research interest in hybrid composites using two or more fillers to realize multiple functions are also increasing. Phase change materials (PCMs) absorb and emit energy through phase transition and can be used as a micro encapsulated structure. In this study, we fabricated hybrid composites using microcapsulated PCM (MPCM) and the natural fibrous filler, kenaf. We aimed to fabricate a composite material with improved endothermic characteristics, mechanical performance, and environmental friendliness. We analyzed the endothermic properties of MPCM and the structural characteristics of two fillers and finally produced an eco-friendly composite material. The PCM and kenaf contents were varied to observe changes in the performance of the hybrid composites. The endothermic properties were determined through differential scanning calorimetry, whereas changes in the physical properties of the hybrid composite were determined by measuring the mechanical properties.

Thermal-regulation of nonwoven fabrics by microcapsules of n-eicosane coated with a polysiloxane elastomer

Abstract Synthesis of microcapsules composed of a paraffin core coated with polysiloxane, which were developed in one of our laboratories, was adapted for preparation of the microcapsules for thermoregulation of textiles. n-Eicosane with melting temperature 37 °C was used as a phase change material (PCM). Shells of the microcapsules were made of a polysiloxane elastomer. The microcapsules were fabricated in an aqueous emulsion, which was prepared by mechanical co-emulsification of the paraffin with a reactive polysiloxane. The process yielded microcapsules consisting of n-eicosane coated with polysiloxane, which later was cross-linked in the emulsion. Chemical structure of the microcapsules was characterized by FT-IR, 29Si MAS NMR and EDX methods. SEM and TEM techniques were used for studies of microcapsule diameters, diameter distributions and thickness of the polysiloxane shells. Core-shell structure of the microcapsules and complete coating of the paraffin with polysiloxane were confirmed. Phase change enthalpy of the microcapsules was 146 J/g. Encapsulation coefficient (Xen) and energy storage coefficient (Xes) were close, which indicated that the absorbed and released heat was due to the melting and crystallization of n–eicosane, respectively. The PCM microcapsules were incorporated into the needled fabrics using a padding method. SEM, FT-IR and EDX determined their presence and location in the fabrics. It was found that content of the PCM microcapsules in the dry mass of the nonwovens was 37 wt percent. The high value of the coefficient energy storage capability (Ces) for the microcapsules alone, for the microcapsules with binder and for the modified nonwoven were close to 99% and indicated a tight encapsulation of the paraffin by polysiloxane shells. This ensured heat absorption and release during in many cycles. Indeed, the DSC results (over 100 cycles of phase changes) confirm high thermal stability of the microcapsules also in the modified nonwoven. The heat effect corresponding to the phase change was equal 34 J per gram of the modified textile.

Development of thermo-regulating fabrics using PCM microcapsules with poly(methyl methacrylate-co-2-hydroxy ethyl methacrylate) shell and n-alkane core

PurposeThe purpose of this paper is to prepare microencapsulated phase change materials (PCMs) and apply them to cotton and wool fabrics for developing thermo-regulating fabrics.Design/methodology/approachMicroencapsulated n-hexadecane and n-octadecane with poly(methylmethacrylate-co-2-hydroxy ethyl methacrylate) shell was prepared. Microcapsules were fabricated using oil-in-water emulsion polymerization method. Their chemical structure, microstructure, thermal energy storage properties and thermal stability were analyzed by Fourier-transform infrared spectroscopy, polarized light microscope, differential scanning calorimeter and thermogravimetric analyzer, respectively. The mean particle size was tested by a particle sized instrument. The microcapsules were applied to the wool and cotton fabrics using pad-dry-cure method. The thermo-regulating property of the fabrics was evaluated using the T-History test. The distribution and durability of the microcapsules on the fabrics was investigated with scanning electron microscopy.FindingsSpherical microcapsules with p(MMA-co-HEMA) shell and n-alkane core have been produced successfully. n-hexadecane in microcapsule solidifies at 14.8−15.6°C with the latent heat of 65.6−129.8 J/g and melts at 16.7−16.9°C with the latent heat of 67.6−136.9 J/g. Microencapsulated n-octadecane solidifies at 25.8−26.3°C with the latent heat of 74.1−106.2 J/g and melts at 26.8−27.4°C with the latent heat of 80.3−113.4 J/g. The microcapsules have enough thermal stability to the temperature of 150°C that was applied during the fixation of microcapsules on the fabric. The thermo-regulating effect of the microcapsule-incorporated fabrics has been proved by the T-history test.Originality/valuePCM microcapsules with p(MMA-co-HEMA) shell and n-hexadecane and n-octadecane core have been produced and their usage to produce thermo-regulating textiles have been proved. To determine the thermo-regulating property of the fabrics treated with these new PCM microcapsules, a T-History system has been designed.

Preparation and evaluation of thermo-regulating bamboo fabric treated by microencapsulated phase change materials

Two types of microencapsulated phase change materials (ENPCMs) were synthesized by polymerization. The core material of ENPCM was n-octadecane and the shell materials were polymethyl methacrylate-butyl acrylate and polymethyl methacrylate-butyl acrylate-hydroxyethyl methacrylate. Subsequently, the synthesized ENPCMs were applied onto bamboo fabric by the dip and dry method. The properties of ENPCMs were analyzed in terms of surface morphology, size distribution and latent heat; the treated bamboo fabrics were evaluated in terms of surface morphology, hydrophilicity, washing fastness and heat storage capacity. The results showed that polymethyl methacrylate-butyl acrylate/ n-octadecane (PMBO) microcapsules had an irregular shape, while polymethyl methacrylate-butyl acrylate-hydroxyethyl methacrylate/ n-octadecane (PMBHO) microcapsules were spherical, and the mean diameters of both microcapsules were less than 1 µm. The latent heat of phase change material (PCM) microcapsules was almost the same at a thermal storage capacity of 110 J/g. There were many more and more even PMBHO microcapsules deposited on bamboo fabric than that of PMBO microcapsules deposited on bamboo fabric. Bamboo fabrics treated by both microcapsules were hydrophilic, and the hydrophilicity of fabric treated by PMBHO microcapsules was even better. The ratio of PCM microcapsules to bamboo fabric was about 1:4, and the latent heat of treated bamboo fabrics was about 20 J/g. Moreover, the treated bamboo fabrics exhibited excellent washing fastness due to the strong binding strength between the highly hydrophilic microcapsules and bamboo fibers. Approximately 72% of PCM microcapsules were retained on the fabric after 15 washing cycles.

Low-temperature organic phase change material microcapsules for asphalt pavement: preparation, characterisation and application

Low-temperature phase change material (PCM) is a material that stores additional heat at elevated temperatures and releases energy when the temperature is below the limit. A way to solve the low-temperature disaster of asphalt pavement is desired to be developed. In this article, a two-component organic low-temperature PCM was encapsulated by melamine-urea-formaldehyde resin and finally reinforced with polypropylene. The reinforced PCM microcapsules were mixed with 70# SBS (Styrene-Butadiene-Styrene) modified asphalt in SMA-10 (Stone Matrix Asphalt-10) to form aggregates. The results showed that after adding 6.0% (w/w) reinforced PCM microcapsules, there was a significant delay compared to a blank sample with a maximum temperature difference of 1.8 °C when the temperature dropped to 0 °C, which proved that this method has a good potential in resisting low-temperature disasters on asphalt pavement and deserves further improvement.

A novel approach of heat recovery system in compressed air energy storage (CAES)

Compressed air energy storage is a useful means of storage since the stored compressed air can be used at any time as a source of mechanical energy for power production. However, if the heat generated during compression is not utilized, the process efficiency will be low, and consequently, additional heat is required to avoid frost formation during the expansion process. The generated heat during compression can be stored in the form of sensible heat in the wall of the high-pressure tank at an elevated temperature. However, this method is undesirable due to (1) less air can be compressed at higher temperatures and (2) heavy insulation would be required to prevent heat loss to the environment over extended time. A solution to this problem is to use Phase Change Material (PCM) which has a melting temperature close to ambient, and hence the heat could be stored as latent heat of melting. PCMs have low thermal conductivity and hence requires to have large contact area with the compressed air so as to be able to release its latent heat rapidly during rapid expansion. This could be achieved through the use of microencapsulated PCM, which provides very large surface area. In this work, a high-pressure tank (2 L, 200 bar) was used for air storage while the commercial microcapsules; Micronal® DS 5038X was used as the latent heat storage material. Both theoretical simulation and experimental measurements made on the system show that the use of PCM microcapsules reduces the maximum increase in air temperature from approximately 45 °C to 27 °C (150 g, Micronal® DS 5038X) during charging. While during discharging, the maximum decrease in temperature was reduced from 48 °C to 28 °C, which prevented air temperature from dropping to below 0 °C.

Preparation of Low-Temperature Phase Change Materials Microcapsules and Its Application to Asphalt Pavement

AbstractAsphalt pavement cracks easily in low-temperature environments. In order to address the problem, phase-change material (PCM) microcapsules working at 0–10°C are used to replace some of the ...

Elucidating the influences of compliant microscale inclusions on the fracture behavior of cementitious composites

The fracture response of cementitious composites containing compliant microencapsulated inclusions and its influence on the fracture process zone (FPZ) are reported. The incorporation of small amounts of phase change material (PCM) microcapsules (replacing up to 10% by volume of sand) is found to slightly improve the strength, fracture toughness, critical crack tip opening displacement (CTODc), and the strain energy release rates. Digital image correlation is used to examine the FPZ at the tip of the advancing crack, to better explain the influences of compliant microscale inclusions on energy dissipation. The FPZ widths are found to slightly increase with PCM dosage but its lengths remain unchanged. The increase in FPZ width is linearly related to the CTODc, showing that inelastic deformations of the crack-tip in the direction of crack opening are indeed influenced by microscale inclusions. It is shown that cementitious systems containing microencapsulated PCMs can be designed to demonstrate mechanical performance (including fracture) equivalent to or even better than their PCM-free counterparts, in addition to the well-described thermal performance.

Ultralight graphene micro-popcorns for multifunctional composite applications

Graphene has been widely applied in polymer nanocomposites due to its charming physical and chemical properties. However, the performance of graphene/polymer composite is hampered by the strong stacking tendency of graphene sheets. Here we introduce graphene micropopcorns (GMPs) with a hollow structure and a low stacking degree as an efficient additive for multifunctional composites. GMPs are massively fabricated via a facile thermal treatment of spray-dried graphene oxide (GO) powder. GMPs feature a low tap density (6–8 mg cm−3), a high specific surface area (947 m2 g−1) and a good solvent absorption capability (62 g g−1). This micro form of graphene can act as electrical conductive fillers with a low percolation threshold of 0.18 vol% and microcapsules of phase change materials with a 358% enhancement in thermal conductivity. Besides, the microwave absorption (MA) performance of GMPs/paraffin composites outperforms most graphene-based materials ever reported but with a record-low filler content (2.5 wt%). The large-scale producible GMPs enable an efficient method to utilize graphene to grant conventional materials with better performances and new functions.