Low Temperature Storage Research Articles

Effect of different storage conditions on dimensional accuracy of 3D-printed dental models.

The objective was to determine the accuracy of 3D-printed dental models subjected to different storage conditions using six different material and printer combinations. Three completely dentate models were designed using dental CAD software (3Shape Dental System). A horseshoe-shaped solid base with a posterior horizontal bar was used. The models were printed in a horizontal direction against the building platform without support. The models were printed using six printers with the corresponding recommended resin material: Carbon M2 (DPR10), HeyGears A2D4K (Model HP UV2.0), Stratasys J5 (MED610), Stratasys Origin One (DM200), Envision One (E-Model LightDLP), and Asiga Pro4K (VeriModel) with a standard layer thickness of 50 μm. All printed models underwent scanning using a laboratory scanner (Sirona inEOS X5) after printing. Subsequently, the models were randomly assigned into three groups of storage conditions, LT: cold environment (4±1°C), HT: hot and dry environment (50±2°C), and RT: room temperature (25±2°C) serving as the control. Each group was kept under the designated condition and was scanned at 1, 2, 3, 4, and 8 weeks. The total number of models (N) was 72, with 6 printers producing 12 models per printer for 3 storage conditions, resulting in 4 models for each storage condition and each printer. The generated STL files were imported into a 3D inspection software for comparison with the original STL files. In-tolerance percentage, the deviation RMS, trueness, and precision were obtained and analyzed with least square mean linear regression using JMP Pro 15 to identify the significant effects (α = 0.05). The in-tolerance percentage as-printed was significantly different among different printers. Significant dimension deviations were observed after the first week of storage at HT and with subsequent weeks of storage. RT and LT did not show significant dimensional changes. Models printed with Carbon M2 showed the highest in-tolerance percentages compared to the other printers. The model deviations were affected by storage conditions and the printer used, with high-temperature storage showed least stability compared to low and room temperatures. No significant difference was observed between low and room temperature storage conditions. The Carbon M2 printer showed the highest accuracy among all printers tested. The region had a significant effect on the deviation measured, with the abutment body showing the least deviation. Among the 3D printers evaluated, A2D4K by HeyGears and Carbon M2 printers demonstrated the highest accuracy in terms of both precision and trueness.

Hexanal Treatment for Improving the Shelf-life and Quality of Fruits: A Review

Fruits are rich sources of bioactive compounds such as lycopene, tannins, β-carotene, resveratrol, and lignan. These bioactive compounds’ antioxidative, antimicrobial, and antidiabetic properties are important in the human diet. Since fruits are one of the major sources of health-promoting nutrients for human consumption, they have high economic value. Ripening is a developmental process which involves changes in the colour, texture, taste, and metabolite composition of fruits, thus affecting their quality. In the market, the good quality of fruits depends on the ripening stage. Rapid ripening could shorten the shelf-life and quality of fruits. Shortened shelf-life causes fruit spoilage during post-harvest, transport, storage, and distribution. In turn, it will cause economic losses in the fruit market. Low-temperature storage is one of the techniques to prolong the shelf-life of fruits. However, this technique requires an expensive facility to achieve and maintain the low temperature. On the other hand, it has been reported that hexanal treatment could prolong the shelf-life and quality of fruits. It is also cheaper and easier to apply. However, the ripening inhibition mechanism of hexanal is not yet fully understood. The effectiveness of hexanal treatment on different fruits is also unclear. Numerous publications on hexanal treatment reported different formulations, techniques, and effectiveness rates on different fruits. Optimised formulation and technique are important to develop an efficient hexanal treatment strategy. Therefore, the mechanism, effectiveness, formulation, technique, and development of hexanal-based products to prolong the shelf-life of fruits are discussed in this review.

Low-Temperature and Fast-Charge Sodium Metal Batteries.

Low-temperature operation of sodium metal batteries (SMBs) at the high rate faces challenges of unstable solid electrolyte interphase (SEI), Na dendrite growth, and sluggish Na+ transfer kinetics, causing a largely capacity curtailment. Herein, low-temperature and fast-charge SMBs are successfully constructed by synergetic design of the electrolyte and electrode. The optimized weak-solvation dual-salt electrolyte enables high Na plating/stripping reversibility and the formation of NaF-rich SEI layer to stabilize sodium metal. Moreover, an integrated copper sulfide electrode is in situ fabricated by directly chemical sulfuration of copper current collector with micro-sized sulfur particles, which significantly improves the electronic conductivity and Na+ diffusion, knocking down the kinetic barriers. Consequently, this SMB achieves the reversible capacity of 202.8mAhg-1 at -20°C and 1C (1C = 558mAg-1). Even at -40°C, a high capacity of 230.0mAhg-1 can still be delivered at 0.2C. This study is encouraging for further exploration of cryogenic alkali metal batteries, and enriches the electrode material for low-temperature energy storage.

Multi-objective optimization for green logistics planning and operations management: From economic to environmental perspective

In the energy crisis and climate change context, the trade-off between economic and environmental objectives of green supply chain management and operations in industrial parks has become increasingly prominent. This paper couples the management of the energy generation, the refrigeratory inventory, and the cold-chain transportation systems of a green industrial park (GIP) for fresh goods that require low-temperature storage. We introduce the renewable energy microgrid (REM) to the energy chain and electric vehicles to the transportation system in the GIP to reduce carbon emissions. A two-phase multi-objective optimization model considering total expenditures and carbon emissions simultaneously is established to compare different renewable and conventional energy schemes. We exploit the real data to optimize scheduling strategies for energy, inventory, and fleet systems under a typical period based on different environmental conditions and time-sharing electricity prices. The empirical study shows that the adoption of REM and electrical vehicles can reduce carbon emissions in the supply chain by 13.6%, and GIP managers with different performance targets should choose different energy mixed schemes.

Influence of Packaging Materials and Size on Shelf Life and Quality of White Button Mushroom during Storage

Background: Because of porous fruit body, high moisture content and extremely high respiration rate, the postharvest shelf life of button mushroom is a bottleneck in the mushroom industry as very high losses are recorded during transportation and marketing if the produce is not handled properly. Methods: NBS-5 strain of white button mushroom was treated with 0.05% potassium meta-bisulphite (KMS) followed by packing in 200, 400, 600, 800 and 1000 g capacity polyethylene (PE) and polypropylene (PP) bags of 150 gauge along with 0.01% vents. Dipping in water and packing in 200 g capacity bags was used as control. The packed mushrooms were stored at ambient (24-25°C and 58-62% RH) and low (4-6°C and 80-82% RH) temperature. Result: A significant increase in PLW (%) was recorded in all the treatments both at ambient and low temperature during storage but the increase was faster at room than refrigerated conditions. The white button mushroom in PE had a shelf-life of 7 and 16 days whereas it was 3 and 7 days, respectively, at ambient and low temperature storage conditions in control. A significant reduction in protein, sugars and phenols was recorded whereas polyphenol oxidase (PPO) increased notably during storage. Pack sizes of 200 and 400 g had an edge over 600, 800 and 1000 g with higher shelf-life at both storage conditions. PE packing was found comparatively better for extension of shelf-life compared to PP. The overall acceptability of button mushroom was also found better in 200 g and 400 g packing. The study revealed that the postharvest shelf-life of white button mushroom var. NBS-5 can be extended up to 16 days by packing in 200 and 400 g packs of PE stored at low temperature after pre-treatment of KMS.

Research of Maillard reaction and stability of liquid infant formulas during storage

SummaryThis study investigated the Maillard reaction (MR) and the stability of liquid infant formulas (LIFs) stored at 5 °C, 25 °C and 40 °C for 6 months. With the increase in storage temperature, the concentrations of 2‐furoylmethyl‐ε‐lysine (furosine) increased from 60.72 to 109.60 mg/100 g protein and Nɛ‐ Carboxy methyl lysine (CML) increased 106.82 to 197.04 mg/100 g protein. Colour became darker, yellower and redder, and pH values decreased. Negative charges increased during the first 3 months and decreased during the last 3 months. Fat globule sizes increased and particle size distribution (PSD) regressed, and the accumulation of fat was clearly observed by confocal laser scanning microscopy (CLSM). Shear thickened with the increase in shear rate, and the turbiscan stability index (TSI) values increased. In summary, these results indicated that lower storage temperature (5 °C) inhibits the MR and reduces unstable changes of LIF during storage period; thus, the nutritional value of LIF can be largely preserved.

Study on the Physical and Rheological Characterisation of Low-Density Polyethylene (LDPE)/Recycled Crumb Rubber (RCR) on Asphalt Binders

Recycled crumb rubber (RCR) is considered a reliable asphalt modifier and a solution to the problem of scrap tyre recycling. RCR-modified asphalt (RCRMA) typically has good low-temperature performance and storage stability. However, the pre-treatment of crumb rubber (CR) impairs its physical properties, resulting in poor high-temperature performance, which limits the industrial application of RCRMA. In this study, low-density polyethylene (LDPE) composite RCR was used to modify asphalt, and LDPE/RCR-composite-modified asphalt (L-RCRMA) was produced to compensate for the deficiencies in the high-temperature performance of RCRMA. The comprehensive physical properties of L-RCRMA were elucidated using tests such as the conventional properties, rotational viscosity, and rheological tests. The results showed that the incorporation of LDPE improved the high-temperature stability and rutting resistance of the asphalt, but an excessive amount of LDPE impaired the low-temperature performance and storage stability of L-RCRMA. Therefore, it is necessary to control the amount of LDPE to balance the performance of the asphalt. On this basis, we recommend a dosage of 20% for RCR and 1.5% for LDPE.

Impacts of Selenium–Chitosan Treatment on Color of “Red Globe” Grapes during Low-Temperature Storage

Maintaining the vibrant color of fruit is a longstanding challenge in fruit and vegetable preservation. Chitosan and selenium, known for their protective and antioxidant properties, have been applied to preserve these produce. This study aimed to investigate the influence of selenium–chitosan treatment (comprising 25 mg L−1 selenium and 1.0% chitosan) on the color of “Red Globe” grapes and to analyze the relative expression of genes associated with anthocyanin synthesis enzymes (VvCHS, VvCHI, VvF3H, VvF3′H, VvF3′5′H, VvDFR, VvLDOX, VvUFGT, VvOMT, Vv5GT, and VvGST) using RT-qPCR. Our goal was to uncover the regulatory mechanisms governing grape color. Comparing various treatments, we observed that selenium–chitosan treatment had a significant effect in reducing decay, maintaining the soluble solids content of grape flesh, and preserving the vivid color of grape. This research indicated that selenium–chitosan treatment slowed down browning and prevented the reduction in total phenolic, flavonoids, and anthocyanin in the grape. Moreover, gene expression analysis revealed that selenium–chitosan treatment increased the expression of VvCHS, VvF3H, VvF’3′H, VvLDOX, and Vv5GT, while also stabilized the expression of VvCHI, VvF3′H, and VvDFR in grape skins. These findings shed light on the potential mechanism by which selenium–chitosan impacts grape color. This study established a theoretical foundation for investigating the molecular mechanisms behind selenium–chitosan’s ability to slow down grape browning and provides a novel approach to enhancing fruit and vegetable preservation techniques.

Low concentration 1-MCP limit ripening process of mango cv. ‘gedong gincu’ during low temperature storage

Mango fruit still ripens and senesces after harvest. The presence of ethylene will shorten the shelf life of mangoes during long transportation processes. The purpose of this research is to find out how long the ‘gedong gincu’ mango (Mangifera indica L.) can be kept at 15°C after being treated with 1-methylcyclopropene (1-MCP). This study conducted experiments in the lab using a completely randomized approach with a single factor that included treatment with and without 500 ppb 1-MCP. Both was kept at 15°C for both sessions. Weight, color, hardness, total dissolved solids, total titrated acid, and chilling injury score were measured in this study. Analysis of data will be conducted using a t-test at α = 5% using Microsoft Analysis Toolpak. The study found that adding 1-MCP to mango cv ‘gedong gincu’ had a significant effect (p<0.05) on its color change, hardness, total titrated acidity, and chilling injury score during storage at low temperatures. This suggests that 1-MCP may be able to delay the ripening process by ethylene and extend the shelf life of ‘gedong gincu’ mangoes when stored at 15°C, thereby contributing largely to food loss prevention.

Solid–Liquid Phase Equilibrium: Alkane Systems for Low-Temperature Energy Storage

The thermal characterization of two binary systems of n-alkanes that can be used as Phase Change Materials (PCMs) for thermal energy storage at low temperatures is reported in this work. The construction of the solid–liquid binary phase diagrams was achieved using differential scanning calorimetry (DSC) and Raman spectroscopy. The solidus and liquidus equilibrium temperatures were determined using DSC for thirty-nine different samples, three for the pure n-alkanes and the remaining for binary mixtures at selected molar compositions and used to acquire the corresponding solid–liquid phase diagrams. The two binary systems of n-octane/n-decane (C8/C10) and n-decane/n-dodecane (C10/C12) are characterized by a eutectic behavior at low temperatures. The eutectic temperature for the system C8/C10 was found at 211.95 K and the eutectic composition appeared at the molar fraction xoctane = 0.87. For the system C10/C12, the eutectic temperature was found at 237.85 K, and the eutectic composition appeared for the molar fraction xdecane = 0.78. This work aims to fulfill the lack of available data in the existing literature, considering the potential application of these systems for low-temperature thermal energy storage. Raman spectroscopy was used to complement the DSC data for the construction of the solid–liquid phase equilibrium diagrams, enabling the identification of the solid and liquid phases of the system. Additionally, the liquidus curve of the phase diagram was successfully described using a modified freezing point depression curve as fitting equation, the absolute root mean square deviation for the data correlation of the C8/C10 and C10/C12 systems being 2.56 K and 1.22 K, respectively. Ultimately, the fitting procedure also enabled a good prediction of the eutectic point for both studied systems.

Rapid testing in the food industry: the potential of Fourier transform near-infrared (FT-NIR) spectroscopy and spatially offset Raman spectroscopy (SORS) to detect raw material defects in hazelnuts (Corylus avellana L.)

The detection of raw material defects, e.g., due to incorrect or excessively long storage, is an important issue in incoming goods inspections in the food industry. Fast and easy-to-use analytical methods for evaluating the usability of raw materials are particularly important. In this study, the applicability of Fourier transform near-infrared (FT-NIR) spectroscopy and spatially offset Raman spectroscopy (SORS) for the detection of raw material defects was evaluated. For this purpose, six hazelnut batches stored at different temperatures, humidity levels, and storage times were used as examples in this pilot study. Classification models of samples before and after the different physical treatments show that the resulting changes can be detected by FT-NIR spectroscopy and SORS at elevated temperature and humidity. When one of the storage parameters is increased, FT-NIR spectroscopy is also useful for detecting differences between sample groups. In contrast, SORS cannot distinguish between pre- and post-stored samples when only one of the storage parameters is increased, making SORS unsuitable for incoming inspection of nuts. FT-NIR spectroscopy analysis is also a fast application, because freeze-drying of the sample material prior to analysis is not required as the results before and after freeze-drying are comparable. Combining the FT-NIR spectroscopy and SORS data in a low-level data fusion improved the classification models for samples stored at low storage temperatures, suggesting that the two methods provide complementary information. In summary, analyzing nuts with FT-NIR spectroscopy and SORS, as shown for hazelnuts, has the potential to identify abnormal samples during incoming goods inspections.

Modified bacterial nanofibril for application in superhydrophobic coating of food packaging

Superhydrophobic coatings applied to food packaging can significantly reduce unnecessary food waste. Inspired by nature, we proposed a simple method to prepare coatings with ecologically correct materials, such as beeswax and bacterial cellulose nanofibrils functionalized with nanoparticles of food silicon dioxide (BW/BCn- SiO2). The morphology of bacterial cellulose nanofibrils shows a strong reaction with SiO2 aggregated on the surface of the cellulosic material. The FTIR results confirm the efficiency of the functionalization. In addition, the functionalized material presents less thermal degradation. BW/BCn- SiO2, with a contact angle of 153° and a slip angle of 3°, features Cassie-Baxter-compatible micro/nanoscale roughness, self-cleaning properties, low-temperature storage stability, excellent adhesion and mechanical durability even after several treatments, considered nontoxic and with remarkable performance in repelling liquid foods with high viscosity, such as honey, yogurt and chocolate sauce. This work highlights the importance of innovations in food packaging that impact food waste, through superhydrophobic, ecological and safe coatings.

Xanthan gum coatings augmented with lemongrass oil preserve postharvest quality and antioxidant defence system of Kinnow fruit under low-temperature storage

Kinnow mandarin is an important citrus fruit that undergoes various postharvest qualitative losses. Therefore, the present study aimed to investigate the effect of polysaccharide-based xanthan gum (XG) coatings and lemongrass essential oil (LG) on the nutritive quality of Kinnow mandarins stored at 5–7 °C, 90–95 % RH for 75 days. The results revealed that in comparison to control the coatings maintained the fruit titratable acidity (TA), soluble solid content (SSC), ascorbic acid (AsA) content, total flavonoid content (TFC), and juice content, along with reduced weight loss and spoilage incidence. The coated fruits also exhibited higher sensory quality, total antioxidant activity (TAA), and activities of enzymes; catalase (CAT), peroxidase (POD), and phenylalanine ammonia-lyase (PAL). At the end of storage, the fruits coated with XG 1.0 % + LG 1.0 % exhibited maximum TA (0.69 %), AsA content (203.5 mg L−1), and TFC (0.21 mg g−1) with minimum weight loss (7.57 %) and spoilage (3.01 %) and SSC (11.87 %). The scanning electron microscopic (SEM) images of the coated fruits also exhibited smooth surfaces with closed stomata pores. Overall, XG 1.0 % + LG 1.0 % proved as a potential postharvest treatment for maintaining the nutritive quality of Kinnow under low-temperature storage.

Microstructural changes in thermochemical heat storage material over cycles: Insights from micro-X-ray computed tomography

This paper studies the effect of successive (de)hydration cycles on the structure of potassium carbonate K2CO3·1.5H2O grains for low-temperature heat storage applications. Such structural changes are caused by exposure of the salt to water vapor or removal of water from it, accompanied by successive swelling and shrinkage. Understanding the material's internal structure is key to predicting its behaviour and optimizing its design. However, due to the simultaneous and persistent occurrence of structural changes and transport mechanisms throughout the process, gaining a complete understanding of the phenomenon can be challenging.Unlike conventional experimental approaches and two-dimensional imaging techniques used for porosity assessment, our study showcases the qualitative and quantitative alterations in the porosity and microstructure of potassium carbonate. This analysis is achieved by using Micro-X-ray computed tomography (Micro-CT). The study focuses on the impact of cycling on grain microstructure, investigating pore volume distribution, radial variation of pore sizes, and density of individual grains. It was noted that the porosity increased from 6.4 % to 19.7 % after seven cycles. Initially, we observed a greater number of pores in the core of the uncycled salt grain. However, after cycling, we noticed a more even distribution, with a higher number of pores in the outer region of the grain, which caused a radial change in porosity. Lastly, this research provides the intrinsic and apparent densities of both non-cycled and cycled potassium carbonate specimens.Micro-CT is a good tool for a better understanding of changes in thermochemical material at a structural level. Calculation of porosity provided a pathway to calculate apparent and intrinsic density. The demonstrated method can be used for a wide range of salt hydrates, enhancing the scope and applicability of this study in the field of low-temperature heat storage applications. Additionally, it gives the measuring parameter needed to calculate energy density and change in volume during the reaction.

Fabrication of poly(vinyl alcohol) foam/gel composite used for cold storage by combing molding foaming and freeze-thawing technologies

Ice, the widely used low-temperature storage material, plays an important role in the short-time cold chain transportation. To avoid water leakage caused by ice melting, special encapsulation is needed, but inevitably leads to the single shape and the poor contact between ice and the cooled object. It is urgent to develop a new type of leakage-proof cold storage material. Accordingly, in this paper, by combing the technologies of molding foaming and freeze-thawing, a novel cold storage material containing poly(vinyl alcohol) (PVA) carrier foam and PVA gel was fabricated. PVA carrier foam mainly provided the strength foundation, while PVA gel locked the absorbed water. With the addition of 7.0 wt% PVA gel into PVA carrier foam, denser and uniform cells were formed, endowing the foam/gel composite with good shape retention. Even after 500 times’ cyclic compression, the compression curve of the composite still coincided with the original one. The further introduction of 2.0 wt% NaCl into PVA gel enhanced the cold storage effect of the composite, i.e., the temperature in an incubation box could reach −2.5 °C and be maintained for 16 h. This novel PVA foam/gel composite was expected to be used as cold storage material for cold chain transport, and thus broadening the practical application of PVA.

Investigation of water adsorption characteristics of MgCl2 salt hydrates for thermal energy storage: Roles of hydrogen bond networks and hydration degrees

Thermochemical energy storage holds great promise in solar energy applications, and MgCl2 hydrate salt is considered a promising material for medium and low-temperature thermochemical energy storage. Understanding the adsorption behavior of water molecules in MgCl2 hydrate salts and uncovering the underlying mechanisms are crucial for designing efficient thermochemical energy storage systems. This paper investigated the water adsorption characteristics of MgCl2 hydrate salt utilizing the Grand Canonical Monte Carlo (GCMC) method and captured the adsorption isotherm and concentration distributions of water molecules in MgCl2 hydrate salts pores at various temperatures. The results demonstrate that at low temperatures, particularly when the pore size is small (D < 0.8 nm), the interconnected hydrogen bond network plays a crucial role in enhancing the water adsorption capacity of pure MgCl2. As the temperature increases, the influence of hydrogen bond networks diminishes, and their impact on the water adsorption capacity becomes negligible. Moreover, the hydration degrees of MgCl2 salt significantly influence their water adsorption capacity. MgCl2·6H2O exhibits the best water-uptake performance, followed by MgCl2·4H2O, while MgCl2·2H2O displays the worst water-uptake performance. These findings shed light on the adsorption behavior of water molecules in MgCl2 hydrate salt and offer valuable insights into the design and optimization of efficient thermochemical energy storage systems. Such knowledge is essential for advancing the utilization of thermochemical energy storage in solar energy applications.

Development of evaporative cooling mobile vending cart for vegetables

Post-harvest losses of fruits and vegetables are impacted by lack of adequate low-temperature storage and transportation facilities. The present traditional vending system of handling fruits and vegetables by street vendors causes loss of weight due to lack of cooling system. Solar powered evaporative cooling vending cart operating at reduced temperature was developed and evaluated for its performance loading vegetables namely spinach, fenugreek, brinjal, tomato, cucumber and chilly in the month of February, April and September. The mean drop in temperature was observed 10.21±0.41°C, 8.97±0.46°C and 3.37±1.21°C, whereas mean per cent-increase in relative humidity was 216.54±46.77%, 184.59±12.63% and 130.20±5% observed inside the storage chamber during the month of February, April and September, respectively. Per cent saving in physiological loss in weight (PLW) was highest (62.5%) in spinach, followed by tomato (57.27%), brinjal (53.62%), cucumber (51.97%), chilly (31.69%) and fenugreek (30.30%) as compared to ambient (control). Saving in weight was more than 0.14kg.kg-1 of vegetables over control.

Fabrication of shape-stable glycine water-based phase-change material using modified expanded graphite for cold energy storage

A shape-stable glycine water-based phase-change material (GPCM) was fabricated herein via natural adsorption using modified expanded graphite (MEG) as a porous carrier. Cetyltrimethylammonium bromide (CTAB) was introduced as a modifier on the surface of expanded graphite (EG) to synthesise MEG, which improved compatibility between EG and GPCM. Furthermore, the adsorption capacities of EG and MEG on GPCM were compared and analysed. The thermophysical properties of the as-prepared MEG/GPCM composite were evaluated using differential scanning calorimetry. Results revealed that MEG modified with 0.1 g of CTAB (MEG-0.1) had the best compatibility with GPCM and its adsorption capacity increased from 73.96% to 84.05% compared with that of unmodified EG. When the MEG content was 14%, the MEG/GPCM composite had a suitable melting temperature of −5.06 °C and high latent heat of 243.80 J/g. Moreover, the thermal conductivity was 1.836 W/(m⋅K), 216.33% higher than that of GPCM. After 100 thermal cycles, and the melting temperature and latent heat of the MEG/GPCM composite only decreased by 1.38% and 6.15% to −5.13 °C and 228.79 J/g, respectively. Thus, the prepared composites exhibited excellent thermal properties and showed great potential in the application of low-temperature cold energy storage and cold-chain transportation.

Research on the low-temperature waste heat storage performance of a novel microencapsulated phase change material with a double-shell encapsulation of hexadecylamine

Phase change materials (PCMs) have the advantages of high energy storage density and the temperature can be kept stable when the phase change process occurs, so they can be widely applied to the recovery of industrial waste heat. In this paper, hexadecylamine (HDA) was selected as PCMs, polystyrene (PS) and calcium carbonate (CaCO3) as wall materials, and PS/CaCO3/HDA microencapsulated phase change materials (MEPCMs) were prepared by ultrasonic emulsification. Then the prepared PCMs were characterized and their properties were tested by using transmission electron microscopy, scanning electron microscopy, X-ray diffraction analyzer, X-ray photoelectron spectrometer, Fourier infrared spectrometer, thermogravimetry, differential scanning calorimetry and other characterization methods. The results showed that PS/CaCO3/HDA MEPCMs with microcapsule structure were successfully prepared with a diameter of about 1.5 μm. The thermal conductivity of PS/ CaCO3/HDA MEPCMs was 0.491 W/(m·K), which was 3.41 times of the thermal conductivity of pure HDA. The highest latent heat of PS/CaCO3/HDA MEPCMs was 33.96 kJ/kg, and no leakage problems occurred. The above results indicate that PS/CaCO3/HDA MEPCMs have good stability and high thermal conductivity, and they have good thermal storage performance at low temperatures.

Composite aerogel incorporating low temperature phase change microcapsules for enhanced thermal insulation

Cryogenic transportation and storage confront significant challenges from harsh weather conditions, heightened energy consumption, and epidemic situations, compelling the need for the creation of exceptionally efficient thermal insulation materials. To address this demand, a composite phase change aerogel was designed in this study through incorporating low-temperature microencapsulated phase change microcapsules (MPCM) into a cellulose nanofiber/polyvinyl alcohol (CNF/PVA) system. The MPCM, consisting of a polyurethane-acrylate (PUA) shell and an n-tetradecane core, exhibited excellent encapsulation performance with leak-proof capability. Remarkable low-temperature phase change energy storage properties were observed, including a phase change temperature of approximately 6 °C and an impressive phase change enthalpy of 112 J/g. The MPCM also demonstrated stability during successive heating–cooling repetitions, maintaining its heat storage capacity and morphology for at least 300 cycles. These exceptional thermal characteristics endowed the resulting aerogel with effective thermal insulation and temperature retardation abilities. Meanwhile, the integration of CNF/PVA as the matrix in the composite aerogel led to minimal degradation of thermal storage performance compared to pure MPCM. Moreover, the addition of MPCM significantly enhanced the compressive strength, reaching 5.6 times that of the neat CNF/PVA aerogel. The composite aerogel showed a notably low density of 0.165 g/cm3 and could be reshaped through heating. This work provides a simple yet effective idea for designing bulk materials with low-temperature phase change capabilities, offering promising prospects in the field of thermal insulation.