Higher Enthalpy Values Research Articles

Preparation and Properties of Thermoregulated Seaweed Fibers Based on Magnetic Paraffin wax@calcium Carbonate Microcapsules

In order to enhance the application of thermoregulated materials, magnetic phase change microcapsules were prepared using a self-assembly method. Paraffin wax was chosen for its fine thermoregulation properties as the core material, while Fe3O4 nanoparticles doped in calcium carbonate served as the hybrid shell material. The microcapsules were then blended with sodium alginate and processed into seaweed fibers through wet spinning. The microstructure, thermal, and magnetic properties of the microcapsules were analyzed using scanning electron microscopy, energy dispersive X-ray spectroscopy, a laser particle size analyzer, an X-ray diffractometer, a differential scanning calorimeter, a thermogravimetric analyzer, and a vibrating sample magnetometer. The thermoregulation of the fibers was evaluated using a thermal infrared imager. The results indicated that the microcapsules had a uniform size distribution and good thermal properties. When the mass fraction of Fe3O4 nanoparticles was 8%, the microcapsules exhibited a saturation magnetization of 2.44 emu/g and an enthalpy value of 94.25 J/g, indicating effective phase change and magnetic properties. Furthermore, the thermoregulated seaweed fibers showed a high enthalpy value of 19.8 J/g with fine shape, offering potential for developing multifunctional fiber products.

Phase change hydrogels with tunable adhesion for wearable thermal management and intelligent healthcare

Intelligent wearable devices integrating real-time health monitoring and on-demand treatment are obtaining widespread attention. However, precise monitoring and prolonged photothermal therapy of human bodies still face significant challenges. Herein, a phase change gel (PCG) with simultaneous strain sensing and photothermal therapy functions was fabricated using sodium sulfate decahydrate (SSD, Na2SO4·10H2O), polyacrylamide (PAM), and polydopamine-modified MXene (PDA@MXene). The PCGs possessed a suitable phase transition temperature and high enthalpy value (128.8 J/g), which provided sufficient thermal comfort. The PAM hydrogel effectively overcame the liquid leakage of SSD and achieved flexibility. PDA@MXene not only imparted the PCGs with excellent photothermal conversion efficiency (93.83 %), but also ensured strong adhesive properties to precisely monitor human motions. Interestingly, the PCGs exhibited temperature-sensitive adhesion ability by triggering the phase transition of SSD, thus obtaining high adhesion to the skin and painless detachment simultaneously. The temperature-induced adhesive PCGs exhibit great application prospects in portable medicine devices.

Multi-modal heat rechargeable phase change composites based on MXene coated core-sheath fiber strategy

In order to maintain the human body temperature within a comfortable range in harsh environments, flexible and wearable thermal management fabrics that can combine energy storage and multi-modal heat recharging ability are urgently needed. Here, a strategy of coaxial electrospinning and spray coating was proposed to prepare the MXene-coated core-sheath phase change fibers to satisfy the above requirement. The hierarchical structure endows the composite film with phase change energy storage and photo/electro-thermal multi-modal heat charging performance. Specifically, the encapsulated paraffin wax (PW) in flexible polyurethane (PU) fibers has a high enthalpy value of 91.7 J/g, meanwhile, the flexible film exhibits excellent photo-thermal performance conversion capability (up to 40 °C under the irradiation intensity of 30 mW/cm2) and electro-thermal conversion capability (up to 40 °C at the voltage of 1.5 V) at extremely low MXene loading (0.23 mg cm−2), which endows the MXene/PU@PW (MPP) ability of “heat recharging” by low light power density or low voltage. The multifunctional fabrics with phase change function and multi-modal heat recharging capacity exhibit great potential application in the design of wearable personal thermal management.

Analysis of Adaptability and Application Potential of Supercritical Multi-Source Multi-Component Thermal Fluid Technology for Offshore Heavy Oil in China

Supercritical multi-source, multi-component thermal fluid is a heavy oil thermal recovery method independently developed by China National Offshore Oil Co., Ltd (Beijing, China). It uses waste liquid at the production end of the production well as the water source, the injection medium temperature exceeds 374 °C, 22.1 MPa, and all the produced flue gas is re-injected. Compared with steam huff and puff technology, supercritical technology has the advantages of high enthalpy value, high heat utilization rate, good oil displacement effect, and being green and pollution-free. In addition, its oil–water treatment cost is low, it can realize the reuse of organic matter, it has a good cost advantage of water treatment under the background of low carbon, and it is a thermal recovery method with great application potential for offshore heavy oil. Therefore, it is necessary to carry out research on the adaptability and application potential of supercritical multi-source, multi-heat flow thermal recovery technology in the sea. Based on the laboratory one-dimensional displacement experiment, this paper reveals the mechanism of heavy oil supercritical multi-source multi-component thermal fluid displacement and the contribution of supercritical components to the displacement effect, and establishes the supercritical multi-source, multi-component thermal fluid numerical simulation characterization method. Combined with the characteristics of offshore heavy oil reserves, the main control factors affecting supercritical multi-source, multi-component thermal fluid development were established by numerical simulation and orthogonal test methods, and the adaptive screening method of offshore supercritical technology was established. The application potential of 670 million tons of offshore heavy oil reserves was evaluated and sorted, and KL 10-2 oilfield was selected as the pilot test oilfield. The results show that supercritical technology has great advantages in oil displacement and water treatment cost reduction, and the results play an important guiding significance for the development of offshore heavy oil technology system and the iteration of new technology.

Adjustment of phase change temperature using KCl to develop composite phase change materials based on super absorbent polymer as carrier for use in building energy conservation

In the present work, a Na2HPO4·12H2O–KCl/SAP composite phase change material (CPCM) adapted to the comfortable indoor temperature of the human body has been successfully prepared. The CPCM was developed by physical mixing of Na2HPO4·12H2O (DSP) as the main PCM, KCl as temperature regulator and super absorbent polymer as carrier. In addition, the CPCM was characterized by various techniques, and its thermal properties were analyzed. The results showed that the phase change temperature (Tm) of DSP could be adjusted from 35.8 °C to 32.7 °C by KCl and the DSP-KCl mixture containing 4 % KCl had a high enthalpy value (241.5 kJ kg−1). The cooling curve test found that adding 0.75 % nano-α-Al2O3 as nucleating agent could greatly reduce the supercooling degree of DSP-KCl mixture to 3.39 °C. Adding 14 % SAP into the mixture can solve the leakage and reduce the supercooling degree and thermal conductivity. The resulting CPCM with 14 % SAP added had appropriate Tm (26.9 °C), high enthalpy value (153.5 kJ kg−1), low supercooling degree (1.34 °C) as well as thermal conductivity (0.3079 W K−1 m−1) and excellent thermal reliability. These results indicated that the CPCM was suitable for the field of building energy conservation.

Green, tough, and heat-resistant: A GDL-induced strategy for starch-alginate hydrogels

Hydrogels fabricated by non-covalent interaction garnered significant attention for their eco-friendly and robust mechanical attributes, and are often used in food, medicine and other fields. Although starch-alginate hydrogels exhibit high adhesion and are environmentally sustainable, their applications are limited due to their low elasticity and hardness. Addressing this challenge, we introduce a solvent-induced strategy using glucolactone (GDL) to fabricate hydrogels with enhanced strength and thermal resilience. Utilizing corn starch with varying amylose contents, sodium alginate and calcium carbonate to prepare a double network structure. This GDL-induced hydrogel outperforms most previous starch-based hydrogels in mechanical robustness and thermal stability. Typical starch-alginate hydrogel had a homogeneous network structure and exhibited a high tensile stress of 407.57 KPa, and a high enthalpy value of 1857.67 J/g. This investigation furnishes a facile yet effective method for the synthesis of hydrogels with superior mechanical and thermal properties, thereby broadening the design landscape for starch-based hydrogels.

Multifunctional MXene/PEDOT:PSS-Based Phase Change Organohydrogels for Electromagnetic Interference Shielding and Medium-Low Temperature Infrared Stealth.

Electromagnetic interference (EMI) shielding and infrared stealth technologies are essential for military and civilian applications. However, it remains a significant challenge to integrate various functions efficiently into a material efficiently. Herein, a minimalist strategy to fabricate multifunctional phase change organohydrogels (PCOHs) was proposed, which were fabricated from polyacrylamide (PAM) organohydrogels, MXene/PEDOT:PSS hybrid fillers, and sodium sulfate decahydrate (Na2SO4·10H2O, SSD) via one-step photoinitiation strategies. PCOHs with a high enthalpy value (130.7 J/g) and encapsulation rate (98%) could adjust the temperature by triggering a phase change of SSD, which can hide infrared radiation to achieve medium-low temperature infrared stealth. In addition, the PCOH-based sensor has good strain sensing ability due to the incorporation of MXene/PEDOT:PSS and can precisely monitor human movement. Remarkably, benefiting from the electron conduction of the three-dimensional conductive network and the ion conduction of the hydrogel, the EMI shielding efficiency (k) of PCOHs can reach 99.99% even the filler content as low as 1.8 wt %. Additionally, EMI shielding, infrared stealth, and sensing-integrated PCOHs can be adhered to arbitrary targets due to their excellent flexibility and adaptability. This work offers a promising pathway for fabricating multifunctional phase change materials, which show great application prospects in military and civilian fields.

Photo-curable bio-based comb/bottle brush epoxy resin/beeswax/copper foam phase change materials with high enthalpy value, high conductivity, and multifunctional properties

At present, the demand for green energy has reached a new height in history, and thermal energy storage technology has been widely used to reduce energy consumption. It is still a challenge to develop bio-based polymeric form-stable phase change materials (FSPCMs) with high enthalpy value and thermal conductivity (TC), short curing time, and multifunctional properties. This work not only exploited a series of adjustable and photo-curable comb/bottle brush bio-based epoxy resin/beeswax (bw) FSPCMs with the above superiorities, but also revealed the effects of cross-linking density on the energy storage capacity and encapsulation rate of the FSPCMs. As a result, the optimal system can encapsulate the maximum amount of bw (60 wt%) and obtain the highest enthalpy value (142.1 J/g) with only 0.5% enthalpy loss. Through further introducing the optimal curing system into the copper (Cu) foam, the electromagnetic interference shielding property, TC, tensile strength, and photo-thermal conversion efficiency of the final composite (modified by Cu of 95% porosity) can reach 110 dB, 2.387 W m−1K−1, 2.81 MPa, and 80%, respectively, and the enthalpy value (84.2 J/g) is still satisfactory. This study can provide theoretical guidance for the structural design of reliable fast photo-curable bio-based polymeric FSPCMs with excellent phase change performances and multifunctional properties.

Stabilization Effect of Potato Starch on Characteristic Flavor Compounds in Onion Sauce

AbstractThe food industry is experiencing a substantial demand for transitioning to natural flavors. Nonetheless, the challenge lies in the inherent instability of most flavor molecules when removed from their original sources. Three representative flavor compounds, including dipropyl disulfide (DD), allyl mercaptan (AM), and dimethyl trisulfide (DT), are selected to form composites with potato starch (PS) to protect them from decomposition or transformation. Then, their physicochemical properties and microstructures are investigated using combined methods. PS can combine with these sulfides mainly through its amylose, and thioethers are more likely to interact with PS than mercaptan. All the composites have lower phase transition temperature and higher enthalpy values than PS, and PS‐AM exhibits the largest stability followed by PS‐DD and PS‐DT. The sulfides interact with PS by entering into the helical cavity of its amylose mainly through hydrophobic interaction and increase the long‐range ordered degree and short‐range ordered degree of the composites. DD, AM, and DT can form V‐type inclusion composites with PS, which reserves more DD and AM to delay flavor degradation and enhances the flavor stability of onion sauce. This study can provide valuable reference for the preservation of characteristic flavors of allium food products during thermal processing and storage.

Composite phase change materials with thermal-flexible and efficient photothermal conversion properties for solar thermal management

Composite phase change material (CPCM) with the advantages of high enthalpy and constant temperature phase change, has been widely used in many fields, such as photovoltaic thermal system, building envelope structure and so on. However, conventional CPCM is often rigid, poor light absorption and low thermal conductivity, which limits the application of solar energy utilization. In this paper, a novel Paraffin wax/Thermoplastic elastomer/Carbon nanotube(PA/SEBS/CNT) with shape stability, thermos-flexibility and high photothermal conversion efficiency was prepared, PA as the phase change material, SEBS as the flexible material and CNT as the light-absorbing material. The results show that the addition of CNT increases the absorbance of PA/SEBS from 0.3 to 1.0, and the photothermal conversion efficiency of PA/SEBS/CNT-10 % is as high as 96.17 %. In addition, the CPCM also has a high enthalpy value of 180 J/g, and a high thermal conductivity of >0.3403 W/(m·K), and also exhibits shape-driven memory. At the same time, outdoor photothermal experiments show that PA/SEBS/CNT has excellent photothermal conversion performance under real sunlight, and the highest temperature can reach 99.51 °C. The new CPCM developed has a broad application prospect in solar thermal systems.

Influence of crystallographic anisotropy on the electrical conductivity of apatite at high temperatures and high pressures

Abstract The electrical conductivity of apatite single crystals along three main crystalline directions was measured in situ using a YJ-3000t multi-anvil apparatus and a combined system consisting of the impedance/gain-phase analyzer (Solartron 1260) and dielectric interface (Solartron 1296) at 973–1373 K and 1.0–3.0 GPa. The obtained results indicate that the relationship between the electrical conductivity and temperature conforms to the Arrhenius relation. At 2.0 GPa, the electrical conductivity of apatite with relatively high activation enthalpies of 1.92–2.24 eV shows a significant anisotropy with an extremely high anisotropic degree (τ = ~8–16) value. For a given [001] crystallographic orientation, the electrical conductivity of apatite slightly decreases with increasing pressure, and its corresponding activation energy and activation volume of charge carriers are 2.05 ± 0.06 eV and 9.31 ± 0.98 cm3/mol, respectively. All of these observed anomalously high activation enthalpy and positive activation volume values suggest that the main conduction mechanism is related to the monovalent fluorine anion at high temperature and high pressure. Furthermore, three representative petrological average schemes, including the parallel, Hashin-Shtrikman upper bound, and average models were selected to establish the functional relation for the electrical conductivity of the phlogopite-apatite-peridotite rock system along with the volume percentages of apatite ranging from 1 to 10% at 973–1373 K and 2.0 GPa. For a typical Hashin-Shtrikman upper bound model, the electrical conductivity-depth profile for peridotite containing the 10% volume percentage of apatite was successfully constructed in conjunction with our acquired anisotropic electrical conductivity results and available temperature gradient data (11.6 and 27.6 K/km) at depths of 20–90 km. Although the presence of apatite in peridotite cannot explain the high-conductivity anomalies in western Junggar of Xinjiang autonomous region, it may provide a reasonable constraint on those of representative apatite-rich areas.

Graphene Functionalization of Polyrotaxane‐Encapsulated PEG‐Based PCMs: Fabrication and Applications

AbstractPhase change materials (PCMs) have received much attention regarding the thermal regulation of electronic devices. However, the main limitations of using organic PCMs are the low thermal conductivity and leakage during the phase change process. This work aims to improve these limitations to increase the thermal conductivity of the leakage‐proof PCM formed by a polyrotaxane that serves as a support material to encapsulate PEG. For this purpose, different contents of graphene nanoplatelets (GNP) are blended. To facilitate its postindustrial production and to meet ecological standards, the synthesis of this PCM is simple and only using water as a solvent. The PCMs can be thermally processed conveniently by a hot press. Furthermore, the PCMs achieve high enthalpy values (132.9–142.9 J g−1) due to the action of GNPs as thermally conductive fillers. The PCMs exhibited an increase of 60–257% in thermal conductivity values with higher GNP content, and show great shape stability and no leakage during phase change. These improvements solve the main problems of organic PCMs, thus making PLR‐PEG‐GNP‐based materials a good candidate for use as thermal energy storage materials in industrial applications as thermoregulators of solid‐state disks or realizing the “shaving peaks and filling valleys” effect for thermoelectric generators.

Experimental study on the characteristics of V‐type arc plasma torch with four electrodes

AbstractThe arc plasma is widely used in various fields due to its excellent advantages, such as elevated temperature, high enthalpy, and increased energy density. Under this direction, a four‐electrode V‐shaped arc plasma torch was developed to increase both the arc power and plasma volume. The arc dynamic characteristics, the volt‐ampere characteristics, and the thermal efficiency of the arc plasma torch were systematically studied. From the acquired results, a large‐scale, and low‐frequency re‐strike process between the arc channels was demonstrated. Compared with the common twin‐electrode structure, the stability of the four‐electrode structure during the discharging process was improved, exhibiting a wider frequency distribution of the re‐strike events. The electrode layout may also affect the dynamic evolution process of the arc. However, from a statistical point of view, no significant differences in electrical characteristics were recorded. The four‐electrode V‐shaped arc plasma torch presented a typical descending volt‐ampere characteristic, and the re‐strike frequency increased with an increase in the current. A high thermal efficiency (above 83%) was obtained in the range of arc current of 80–200 A. At a current value of 200 A, the jet enthalpy and the average gas temperature can reach 17.41 MJ/kg and 6590 K, and the corresponding jet length was close to 80 cm because of both the high thermal efficiency and enthalpy. The stable discharge process, high thermal efficiency, high jet enthalpy value, and large volume rendered the proposed four‐electrode V‐shaped arc plasma torch to be suitable for various applications including nanomaterial preparation, metal powder spheroidization, etc.

A novel in-situ growth ZIF-67 on biological porous carbon encapsulated phase change composites with electromagnetic interference shielding and multifunctional energy conversion

With the current intricate application environment, extended versatility is critical to the future development of phase change materials (PCMs). Herein, we prepared a series of phase change composites (PCCs) with excellent electromagnetic interference shielding effectiveness (EMI SE) and versatile thermal management. Specifically, the hybridized multi-stage porous biological carbon base with magnetic and electrical conductivity was prepared as the substrate material for encapsulating paraffin wax (PW) by carbonizing in situ growth ZIF-67 on waste agricultural. The synergy between the functions of the porous biological carbon and PW makes the PCCs have high-performance EMI SE (44.81 dB) and high enthalpy value (175.88–229.52 J/g) at the identical time. In which CC-ZIF-3 @PW has outstanding effect in storing and releasing thermal energy for photo-thermal, magnetic-thermal and electric-thermal conversion. Unsurprisingly, the PCCs breaks innovative ground for energy storage and conversion materials with potential value in various fields such as electronic protection, deicing and thermal energy utilization.

Structural characteristics and thermal performances of lauric-myristic-palmitic acid introduced into modified water hyacinth porous biochar for thermal energy storage

Water hyacinth (WH) was used to prepare biochar for phase change energy storage field to realize encapsulation and enhance thermal conductivity of phase change materials (PCMs) in this work. The maximum specific surface area of modified water hyacinth biochar (MWB) obtained by lyophilization and carbonization at 900 °C was 479.966 m2/g. Lauric-myristic-palmitic acid (LMPA) was used as phase change energy storage material, LWB900 and VWB900 were used as porous carriers respectively. Modified water hyacinth biochar matrix composite phase change energy storage materials (MWB@CPCMs) were prepared by vacuum adsorption method, with loading rates of 80 % and 70 % respectively. The enthalpy of LMPA/LWB900 was 105.16 J/g, which was 25.79 % higher than that of LMPA/VWB900, and the energy storage efficiency was 99.1 %. Moreover, the introduction of LWB900 increased the thermal conductivity (k) of LMPA from 0.2528 W/(m·K) to 0.3574 W/(m·K). MWB@CPCMs have good temperature control capability, and the heating time of LMPA/LWB900 was 15.03 % higher than that of LMPA/VWB900. In addition, after 500 thermal cycles, the maximum change rate of enthalpy of LMPA/LWB900 was 6.56 %, and it maintains a phase change peak, showing better durability than LMPA/VWB900. This study shows that the preparation process of LWB900 is the best, and the adsorption of LMPA has high enthalpy value and stable thermal performance, realizing the sustainable development of biochar.

Bead-free and beaded electrospun phase change fibers: A comparative study

Hydrocarbon (n-eicosane)-loaded poly(ethylene oxide)/poly(methyl methacrylate) (PEO/PMMA) blended fibers exhibiting bead-free and beaded morphologies were fabricated by means of the electrospinning technique using chloroform as the processing solvent and systematically compared in respect to their phase change behavior. Their morphological characteristics were determined by Scanning Electron Microscopy (SEM), which revealed their highly porous structures, while their chemical composition and structural properties were examined by Fourier Transform Infrared Spectroscopy (FTIR) and X-Ray Diffraction (XRD) spectroscopy, respectively. Thermogravimetric analysis (TGA) and Differential Scanning Calorimetry (DSC) were implemented for obtaining information on the materials’ thermal properties. The heating–cooling cycles up to 48 °C revealed that in both sample series (i.e. bead-free and beaded fibers), the melting temperature increases by increasing the n-eicosane content. The temperature of the first crystallization peak (higher temperature) showed a minimal variation, while the temperature of the second peak (lower temperature) increased upon increasing the n-eicosane content. All investigated materials exhibited excellent repeatability in consecutive heating–cooling cycles, with significantly low supercooling and high enthalpy values. Interestingly, regardless of their morphology (bead-free or beaded), both series were found to be suitable as phase change materials for a wide range of n-eicosane content values. Additionally, the supercooling values recorded in the two series with the same n-eicosane content (10–20%) were nearly indistinguishable.

Molecular Regulation of Flexible Composite Solid-Solid Phase Change Materials with Controllable Isotropic Thermal Conductivity for Thermal Energy Storage.

In recent years, graphene has been introduced into phase change materials (PCMs) to improve thermal conductivity to enhance the heat transfer efficiency in thermal energy storage. However, graphenes tend to aggregate in PCMs, leading to the low thermal conductivity efficient enhancement (TCEE), anisotropic thermal conductivity, and deterioration of mechanical performance of PCMs. In this work, we fabricated biomimetic thermally conductive solid-solid PCMs (SSPCMs) by facile blending of the graphene into well-designed polyurethane SSPCMs, in which the graphene established a controllable and highly efficient isotropic thermally conductive pathway based on the π-π stacking between the graphene and the polymer aromatic ring segment. The as-fabricated SSPCMs showed high TCEE (156.78%), excellent flexibility (328% elongation at break), high enthalpy value (>101 J/g), and solid-solid phase transition properties, under 2% loading of graphene. The proportion of in-plane to through-plane thermal conductivity can be adjusted by an elaborate design of the aromatic ring segment in polyurethane SSPCMs. We further demonstrated mechanical flexibility and photothermal property of the composites to reveal their potential in practical applications.

Physicochemical and Technofunctional Comparison of Starch from Varieties of Native Potato (Solanum Phureja) with Commercial Starches

Due to the high genetic variability of the potato, the starch can exhibit different properties of interest to the industry. With the present investigation, it is intended to know these differentiating characteristics in comparison with commercial sources that can be useful in different sectors. Therefore, the objective of this research was to establish a comparison between potato starches extracted from native varieties (Solanum phureja) with commercial potato and corn starches. A physicochemical analysis was carried out, for which characteristics such as amylose content, phosphorus, resistant starch (RS), slow digestibility starch (SDS), rapid digestibility starch (RDS), granule shape, granule size and crystallinity were evaluated. The technofunctional analysis included variables such as amylographic, thermogravimetric and differential scanning calorimetry analysis. The starches of the native varieties exhibited differential characteristics with respect to the commercial starches. Andina variety obtained the highest peak viscosity (8714 cP), followed by Ratona Blanca starch (6148 cP). In addition, these two varieties had the highest content of resistant starch (33.14±0.8) % and (28.9±0.7) % respectively), higher content of amylose (33.9 % and 35.5 % respectively), phosphorus (>0,08 % for both varieties), high crystallinity and higher enthalpy values (> 19 J/g for both varieties), which make them materials of potential use in different industries. The correlations presented between variables such as resistant starch (RS), enthalpy and crystallinity, showed possible differences at the structural level, which highlighted the differential characteristics of each starch.

Lipophilic Modified Hierarchical Multiporous rGO Aerogel-Based Organic Phase Change Materials for Effective Thermal Energy Storage.

In the field of thermal energy storage, organic phase change materials (PCMs) are widely used as functional materials to boost thermal applications. However, there is often a tradeoff between constructing shape-stable composite PCMs with high enthalpy value and those with low leakage rates. Here, we proposed a promising scheme to address this issue. A novel hydrogel consisting of reduced graphene oxide (rGO) and covalent organic framework (COF) was prepared via hydrothermal methods, and the rGO-COF ultralight aerogel with a hierarchical porous structure was formed after freeze-drying. The rGO-COF aerogel shows excellent absorption ability and affinity for organic solvents. It can sufficiently adsorb the molten organic PCMs, such as polyethylene glycol (PEG), and synthesize shape-stable composite PCMs with excellent leak resistance. The COF grown on the surface of rGO has a superior affinity for PEG, so rGO-COF aerogel shows an outstanding PEG loading rate of up to 96.1 wt %, which is 1.7 wt % higher than that of rGO aerogel. In addition, the COF effectively reduces the subcooling of PEG/rGO-COF with 20.3%, compared to PEG/rGO. Meanwhile, the prepared PEG/rGO-COF exhibits extremely high enthalpy and relative enthalpy efficiency (164.6 J/g, 97.4%). This demonstrates that a promising direction was highlighte for the preparation of high-enthalpy shape-stable composite organic PCMs in this work.

Relationship between cross-linking network structure and phase change performances toward multifunctional epoxy/bio-based wax form-stable phase change materials

High encapsulation rate resulting from the good compatibility between cross-linking network and encapsulated solid–liquid phase change materials (SLPCMs) cannot necessarily result in high enthalpy value for the polymeric PCMs. However, the inner mechanism considering the above fact is not clear due to the lack of suitable model compound systems. In this work, a type of epoxy resin with crystalline alkyl side chains (named D18) and four types of amine curing agents (with similar structure but different polarity and molecular size) were primarily used as the model compound to achieve the encapsulation of beeswax (Bw, a kind of bio-based wax), and then the influence of the cross-linking network structure (using different curing agents) on the phase change performances of the D18/Bw polymeric form-stable PCMs (FSPCMs) was systematically studied. The results suggest that polarity effect and steric hindrance effect are the two factors that affect the phase change performances of the polymeric FSPCMs. Though the encapsulation rate of Bw is the highest (near 70 wt%) in the EPH-Y systems (using 1,3-Cyclohexanebismethylamine as the curing agent), it is the EPM-60 sample (using M−Xylylenediamine as the curing agent and containing 60 wt% Bw) that exhibited the highest enthalpy value of 146.2 J/g. Subsequently, different amount of multi-walled carbon nanotubes (CNT) was introduced to improve the thermal conductivity (TC) and achieve multifunctionalization of the EPM-60 sample. The TC, electromagnetic interference (EMI) shielding performance, and contact angle of the 30 wt% CNT modified EPM-60 sample can reach 1.37 W/mK, 37.4 dB, and 137°, while the enthalpy value can remain 101.1 J/g. This work is very helpful in clarifying the relationship between cross-linking network structure and phase change performances of polymeric FSPCMs, so as to providing theoretical guidance for the cross-linking network structure optimization in preparing other reliable polymeric FSPCMs with high enthalpy value, high reliability, and multifunctionalization.