Thermal Insulation Properties Research Articles

Bending performance and failure modes of sinusoidal corrugated sandwich panels fabricated using stereolithography technology: Effects of geometric parameters

The sinusoidal wave corrugated sandwich panel is an exceptional component with outstanding performance, making it highly suitable for both military and civilian applications. Its strength, rigidity, lightweight nature, low density, simple structure, cost-effectiveness, high load-carrying efficiency, remarkable load-bearing capacity, as well as excellent sound insulation and thermal insulation properties, have positioned the sinusoidal wave corrugated sandwich panel as an ideal choice for energy absorption devices. To evaluate the bending performance of the sinusoidal wave corrugated sandwich panel, this study fabricated single-layer and double-layer sinusoidal wave core sandwich panels using the light-curing molding process described in this research. The research analyzed the impact of various geometric parameters, including skin thickness, core layer thickness, core height, and corrugation wavelength, on the bending performance and failure modes of the single-layer sinusoidal wave core sandwich panels through three-point bending loading tests. The failure modes of the sinusoidal wave corrugated sandwich panel were validated using finite element simulation. Additionally, the study examined the bending performance of the sandwich panels with double-layer sinusoidal wave cores and investigated the influence of wavelength distribution in the upper and lower core layers on the force–displacement curve and energy absorption capacity of the double-layer sinusoidal wave core sandwich panel. These findings provide valuable theoretical support for the design of lightweight and high-strength sandwich panels.

Numerical Modeling of the Thermal Insulating Properties of Space Suits.

The purpose of this study was to model the thermal insulating properties in an exemplary multi-layer layup of space suits utilizing computer simulation techniques and physics and mathematical models. The main system responsible for thermal insulation is the Thermal Micrometeoroid Garment (TMG) material layup. Its structure consists of eight layers with different functions. The utilized textile materials are Rip-Stop-type fabrics, strengthened with the addition of a stronger fiber at fixed intervals. The state variable in thermal problems is the temperature field inside the analyzed TMG. The results obtained from the computer simulation were compared to verification calculations from the mathematical model, which allowed for an assessment of the models' quality and the obtained results. Two numerical models were analyzed in Ansys Workbench software. This enabled an assessment of the model's quality and the possible discrepancies. The modeling of the structure was carried out using the Finite Element Method. The possibility of using this exemplary material layup for a suit was verified using normalized data for an adult in outer space.

Large-scale fabrication and characterization of SiC nanowire thermal insulation paper by a traditional handcraft paper-making process

SiC nanowire paper composed of SiC nanowires, possesses extensive industrial applications owing to its remarkable properties of low thermal conductivity, fire resistance and foldability. In this work, centimeter-scale SiC nanowires were successfully synthesized via a sol-gel and carbothermal reduction reaction. Subsequently, the simple and convenient traditional handcraft paper-making process enables the non-oriented intertwining of nanowires, forming a paper-like structure. Experimental results show that the thermal conductivity of silicon carbide nanowire paper with a thickness of 0.7 mm is 0.041 W/m∙K at room temperature, which is far lower than that of the traditional porous ceramics because of its nanoporous structure. Moreover, upon heating the nanowire paper to 300 °C, a significant temperature difference of approximately 150 °C was observed between its front and back surfaces, and it was able to withstand the butane flame (∼1300 °C) heat treatment for a long time, which indicated that the nanowire paper had obvious low thermal conductivity, good thermal insulation and refractory properties. These characteristics ensure the promising application of SiC nanowire paper for thermal insulation and fire resistance applications.

Balanced Thermal Insulation, Flame-Retardant and Mechanical Properties of PU Foam Constructed via Cost-Effective EG/APP/SA Ternary Synergistic Modification.

To address the challenge of balancing the mechanical, thermal insulation, and flame-retardant properties of building insulation materials, this study presented a facile approach to modify the rigid polyurethane foam composites (RPUFs) via commercial expandable graphite (EG), ammonium polyphosphate (APP), and silica aerogel (SA). The resulting EG/APP/SA/RPUFs exhibited low thermal conductivity close to neat RPUF. However, the compressive strength of the 6EG/2APP/SA/RPUF increased by 49% along with achieving a V-0 flame retardant rating. The residual weight at 700 °C increased from 19.2 wt.% to 30.9 wt.%. Results from cone calorimetry test (CCT) revealed a 9.2% reduction in total heat release (THR) and a 17.5% decrease in total smoke production (TSP). The synergistic flame-retardant mechanism of APP/EG made significant contribution to the excellent flame retardant properties of EG/APP/SA/RPUFs. The addition of SA played a vital role in reducing thermal conductivity and enhancing mechanical performance, effectively compensating for the shortcomings of APP/EG. The cost-effective EG/APP/SA system demonstrates a positive ternary synergistic effect in achieving a balance in RPUFs properties. This study provides a novel strategy aimed at developing affordable building wall insulation material with enhanced safety features.

Environment-friendly, high-performance cellulose nanofiber-vanillin epoxy nanocomposite with excellent mechanical, thermal insulation and UV shielding properties

With the increased demand for biobased epoxy thermosets as an alternative to petroleum-based materials in various fields, developing environment-friendly and high-performance natural fiber-biobased epoxy nanocomposites is crucial for industrial applications. Herein, an environment-friendly nanocomposite is reported by introducing cellulose nanofiber (CNF) in situ interaction with lignin-derived vanillin epoxy (VE) monomer and 4, 4´-diaminodiphenyl methane (DDM) hardener that serves as a multifunctional platform. The CNF-VE nanocomposite is fabricated by simply dispersing the CNF suspension to the VE and DDM hardener solution through the in-situ reaction, and its mechanical properties and thermal insulation behavior, wettability, chemical resistance, and optical properties are evaluated with the CNF weight percent variation. The well-dispersed CNF-VE nanocomposite exhibited high tensile strength (∼127.78 ± 3.99 MPa) and strain-at-break (∼16.49 ± 0.61 %), haziness (∼50 %) and UV-shielding properties. The in situ loading of CNF forms covalent crosslinking with the VE and favors improving the mechanical properties along with the homogeneous dispersion of CNF. The CNF-VE nanocomposite also shows lower thermal conductivity (0.26 Wm−1K−1) than glass. The environment-friendly and high-performance nanocomposite provides multiple platforms and can be used for building materials.

Research on the heat resistance and electrical properties of fluorinated polyimide/nano-Al2O3/nano-Si3N4 composite materials

Polyimide (PI) refers to a polymer containing an imide ring characteristic structure on the main chain. It has excellent thermal stability, insulation properties and other characteristics. The Tesla transformer is the core component of the primary pulse source of the high-current electron beam accelerator. It is also an essential component of the energy storage pulse power supply. Therefore, it has broad application prospects in the fields of national defense and civil industry. If the insulation performance of the turn-to-turn coils of the Tesla transformer does not meet the standards, it will break down during high-voltage corona discharge, causing transformer failure. Therefore, it is crucial to improve the insulation performance of Tesla transformer inter-turn wrapping materials. The incorporation of fluorine-containing groups has proven to be a transformative strategy that significantly enhances the physical, chemical, optical, and electrical properties of PI films. In addition, numerous studies have demonstrated that introducing inorganic fillers into the polyimide matrix can substantially enhance the insulating properties of polyimide films. This paper specifically concentrates on elevating the insulating and thermal attributes of polyimide. Initially, a range of polyimide films was synthesized for performance assessment by employing various fluorinated dianhydride and diamine components, utilizing them as substrates. Then, we used nano-silicon nitride (nano-Si3N4) and nano-alumina (nano-Al2O3) as doping phases to prepare PI composite films, which reduced the dielectric constant and increased the breakdown strength.

Effect of localization–delocalization transition on thermoelectric properties of Bi2Te2Se topological insulator

The thermal transport properties of Bi2Te2Se topological insulators show a range of complex features. Large bulk resistivities coexisting with prominent Shubnikov–de Haas quantum oscillations and proximity to metallic states mark this p-band system as an unconventional topological quantum material. Here, using the density functional plus dynamical mean-field theory method, we show how localization–delocalization transition underpins the T-dependence of thermoelectric responses from room down to low temperatures. We present the implications of our many-particle analysis to resistivity, Seebeck coefficient, thermal conductivity, and Lorenz number and propose that related broadband systems close to electronic transitions could be of use in thermoelectrics.

The Effect of Incorporating Juncus Fibers on the Properties of Compressed Earth Blocks Stabilized with Portland Cement

This study investigates the impact of incorporating Juncus fibers (JF) into compressed earth blocks (CEBs) stabilized with varying Portland cement contents, aiming to enhance local construction materials’ performance and reduce housing costs. CEB composites were produced with soil stabilized using different cement contents (4%, 8%, and 12% by weight) and JF reinforcement (0 to 0.2% by weight), compressed at 10 MPa with a hydraulic press. After 28 days of drying, the CEBs underwent diverse experimental characterizations to assess their physical, mechanical, thermal, and durability properties. The results revealed that incorporating JF led to a reduction in unit weight, ultrasonic pulse velocity (up to 36%), and dry compressive strength (approximately 17%). Higher fiber content correlated with increased water absorption and an increased capillarity coefficient. Thermal conductivity analysis indicated improved thermal performance, decreasing from 0.4350 W/m·K (12% cement without fibers) to 0.2465 W/m·K (4% cement with 0.2% JF). Despite the decrease in mechanical strength, CEBs with lower cement (4%) and higher fiber content (0.2%) demonstrated satisfactory durability (abrasion and erosion) and thermal insulation properties. This research suggests the potential of this material as a promising composite for the building materials industry. The findings contribute valuable insights into sustainable construction materials and have implications for cost-effective housing solutions.

On-Demand Preparation of Boron Nitride Nanosheets for Functional Nanocomposites.

Boron nitride nanosheets (BNNSs) have garnered significant attention across diverse fields; however, accomplishing on-demand, large-scale, and highly efficient preparation of BNNSs remains a challenge. Here, an on-demand preparation (OdP) method combining high-pressure homogenization and short-time ultrasonication is presented; it enables a highly efficient and controllable preparation of BNNSs from bulk hexagonal boron nitride (h-BN). The homogenization pressure and number of cycles are adjusted, and the production efficiency and yield of BNNSs reach 0.95g g-1h-1 and 82.8%, respectively, which significantly exceed those attained by using existing methods. The universality of the OdP method is demonstrated on h-BN raw materials of various bulk sizes from various producers. Furthermore, this method allows the preparation of BNNSs having specific sizes based on the final requirements. Both simulation and experimental results indicate that large BNNSs are particularly suitable for enhancing the thermal conductivity and electrical insulation properties of dielectric polymer nanocomposites. Interestingly, the small BNNS-filled photonic nanocomposite films fabricated via the OdP method exhibit superior daytime radiative cooling properties. Additionally, the OdP method offers the benefits of low energy consumption and reduced greenhouse gas emissions and fossil energy use. These findings underscore the unique advantages of the OdP method over other techniques for a high-efficiency and controllable preparation of large BNNSs.

Thermal insulation properties of materials for fishing vessel coolboxes

Abstract Effective insulation is critical for traditional fishing boats because it helps to maintain the quality of the fish catch. Inadequate insulation can lead to significant economic losses for fishermen, as they may have to discard or sell the fish at a lower price. This study aimed to compare the thermal conductivity properties of three different insulation materials: Petung bamboo, polystyrene foam, and polyurethane foam. The experiment involved testing the density of the materials and conducting thermal conductivity tests. The results indicated that polyurethane foam is the best material for insulation because it has the lowest thermal conductivity value compared to laminated bamboo and polystyrene foam. The addition of more isocyanate mass fraction to the polyurethane foam material can increase its density and strength. This is because increasing the isocyanate concentration increases the cross-linking density of the foam, making it more durable and resilient. Moreover, higher density polyurethane foams exhibit lower heat conductivity, indicating better insulation qualities. This study highlights the importance of effective insulation to maintain the quality of the fish catch. The findings suggest that polyurethane foam, particularly with increased isocyanate concentration, is the most suitable material for insulation due to its superior insulation qualities.

An efficient fabrication method of lightweight aramid nanofibrous aerogels for high-efficient sound absorption and thermal properties

The aramid nanofibrous aerogels (ANFs) have various application prospects due to their ultra-light, high porosity and excellent properties of aramid fibers. However, the preparation of ANFs requires long preparation time and their ultra-dense pore structure leads to poor sound penetration and high sound energy reflectivity, which ultimately makes the overall sound absorption performance of ANFs poor. Therefore, a strategy for synthesis of ANFs is designed to achieve light weight, excellent thermal insulation performance and significantly improve sound absorption properties. This strategy combines cell pulverizing, pump-filtration molding, and directional freezing to ensure structural strength of the aerogel without the addition of cross-linking agents, and this process enables the ANFs to introduce in macro-pores while keeping nano-pores. The structure of multi-layered pores effectively reduces the reflectivity of incident acoustic energy and improves the sound absorption coefficient. The interconnected macro-pores and interlaced small pores of ANFs provide good sound absorption performance (sound absorption average (SAA) = 0.338), excellent flame retardant and thermal insulation properties (thermal conductivity = 0.0635 W (m*K)−1) with ultralight (density = 40.5 mg cm−3) in a thinner thickness (15 mm), which extend the potential of ANFs in areas of noise control and thermal insulation. In addition, the structure of multi-scaled pores can also be formed inside other aerogels by using the method of cell pulverization and filtration preparation, which can be helpful for improving their properties of thermal insulation and sound absorption.

Performance Evaluation of Thermal Insulation Rubberized Mortar Modified by Fly Ash and Glass Fiber

The utilization of waste rubber as a viable option for manufacturing building materials holds great significance for the sustainable development of the construction industry. This study explores the addition of two additives, fly ash (FA) and glass fiber (GF), to rubberized mortar in order to improve its performance. The impact of different waste rubber powder (RP) replacement rates and modified additive dosages on the performance of rubberized mortar, including fluidity, mechanical properties, drying shrinkage, impact resistance, and thermal insulation properties, was investigated. Furthermore, the analytic hierarchy process (AHP) was adopted to study the priorities of the rubberized mortar modified by FA and GF. The results indicate that the addition of RP leads to a decrease in mortar fluidity, mechanical properties, and drying shrinkage. However, it can enhance its impact resistance and thermal insulation properties. The additives, FA and GF, have a significant influence on the properties of rubberized mortar. By means of AHP method analysis, this study concludes that the optimal comprehensive properties of FA- and GF-modified rubberized mortar can be achieved by replacing 10% of sand with RP and using 10% FA and 0.4% GF. This study presents a configuration method for modified thermal insulation rubberized mortar, and it may lead to FA and GF being considered potential candidates for developing environmentally friendly building materials.

Cellulose nanofibrils as a bio-based binder for wood fiber composite insulation panels with enhanced thermo-mechanical properties for structural wall sheathing applications

A low-density wood fiber insulation panel (WIP) composite was developed with 100 % petrochemical-free, bio-based binder with high mechanical strength, water resistance and thermal insulation properties. This study investigated the manufacturing process of composite WIPs made with mechanical pulp fibers with cellulose nanofibrils (CNFs), lignin-containing CNFs (LCNFs), hybridized CNFs-LCNFs, and CNFs-starch as a binder on different scales and evaluated the effects of binder type and content on the panels’ physical, mechanical, and thermal properties. All panels had excellent thermal resistivity values, which increased with the decrease in density. The WIPs made with LCNFs as binder had lower mechanical properties, but it was possible to replace 20 % CNFs with LCNFs to obtain the same performance as neat CNFs as the binder. Untreated panels had poor water resistance but the water absorption properties were significantly improved with the addition wax. The WIPs made with 5 % and 7.5 % binder content and 2 % wax addition could fulfill the criteria of regular and structural wall sheathing applications, respectively. Overall, the results confirm the potential of CNFs and LCNFs to be used as 100 % bio-based adhesives to produce eco-friendly composite WIPs with excellent thermo-mechanical properties to be used for regular and structural wall sheathing applications.

Towards sustainable building solutions: Development of hemp shiv-based green insulation material

There is currently a growing need for sustainable and environmentally friendly materials. One promising candidate is hemp shiv, which is considered waste material. hemp shiv exhibits lightweight properties and high insulation capabilities. This study focuses on the development of a material based in hemp shiv, recycled cardboard fibers is used as binder material, with the addition of a vegetable coating (colophony and arabic gum) for moisture protection and citric acid to enhance cellulose crosslinking. Thermal insulation properties were assessed measuring the heat transfer through the material. Acoustic insulation properties were evaluated using a Kundt tube within a frequency range of 100–6500 Hz. Mechanical tests, including compression, shear, and bending, were performed to assess the material’s strength. Additionally, moisture and fire resistance properties, as well as microstructure analysis, were examined. The influence of citric acid in the cellulose crosslinking was verified using FTIR-ATR spectroscopy. Results demonstrated that a higher percentage of hemp shiv content led to improved insulation performance, achieving attenuation values greater than 0.85–0.95 dB/dB and a thermal conductivity of 0.02–0.03 W/m K. These findings indicate a great performance compared to commercial materials. The coating shields the material from external factors. It was observed that the citric acid does not react with hemp shiv.

Effect of chitosan on the insulation and smoke absorption properties of expanded vermiculite composites

ABSTRACT In order to improve the thermal insulation and smoking properties of expanded vermiculite matrix composites, a kind of expanded vermiculite (EV)/chitosan (CS) composites was prepared by hot pressing. The effects of CS on smoke density, fire-resistance, insulation, and mechanical properties of the EV/CS composites were studied. The results show that with the increase of CS content, the smoke absorption performance and energy storage modulus of the composites is improved. Thermogravimetric (TG) analysis shows that the thermal stability of the EV/CS composite is improved by the presence of chitosan. The pores appear on the surface of the composites after the single-side fire-resistance test. After that, the thermal conductivity of the composites gradually decreases and the insulation performance is improved as the CS content increases. The CS carbonized during the preparation of the composites and thermal decomposition during the test. The morphology results show phase separation of the composites, and the porosity of the composites increases after the test. The reticular structure formed between the EV particles, sodium silicate, and CS molecules reduces the strength loss of the composites.

Advanced hydrostable, recyclable and degradable cellulose hybrid films as renewable alternatives to synthetic plastics

Strong, tough and sustainable materials are in high demand in various engineering applications. We demonstrate a potential sustainable hybrid film made from natural cellulose and a biobased slurry. Through a simple and scalable approach, cellulose can be processed into an advanced material with over 2.8 and 9.2-fold increase in dry strength and toughness after curing and a 728-fold increase in wet strength, respectively. In addition, these hybrid composite films display an outstanding antioxidant activity surpassing 90 %, along with excellent ultraviolet radiation shielding and thermal insulation properties. Further, the hybrid films can be fabricated by integrating all-natural materials and still guarantee their unique functionality. We also demonstrate the feasibility of a circular bioeconomy by recycling the hybrid film using a green, deep eutectic solvent to fabricate a recycled hybrid film that displays excellent mechanical and optical properties. When recycling is unsuitable or economical, the hybrid film can naturally degrade in the soil under 6 months. These encouraging findings suggest the promise of cellulose hybrid films as a renewable, low-cost, tough, and strong material with the potential to replace nonrenewable synthetic plastics and products.

POROUS FLY ASH-BASED GEOPOLYMER USABLE AS AN UNCONVENTIONAL CONSTRUCTION MATERIAL

Geopolymer foam with thermal insulation properties was made by foaming the alumino-silicate mixture composed of fly ash and clay brick waste activated with alkaline activator (water glass and sodium hydroxide in aqueous solution). Other mixture components were expanded perlite as siliceous additive, usual fine aggregate (quartz sand), and less frequently used surfactant (olive oil). The main characteristics of the geopolymer foam were: low density, low thermal conductivity, and relatively high compressive strength. The residual materials contributed to low costs and the complete replacement of ordinary cement led to the significant reduction of CO2 emissions.

Eco-friendly bamboo pulp foam enabled by chitosan and phytic acid interfacial assembly of halloysite nanotubes: Toward flame retardancy, thermal insulation, and sound absorption

Lightweight, porous cellulose foam is an attractive alternative to traditional petroleum-based products, but the intrinsic flammability impedes its use in construction. Herein, an environmentally friendly strategy for scalable fabrication of flame-retardant bamboo pulp foam (BPF) using a foam-forming technique followed by low-cost ambient drying is reported. In the process, a hierarchical structure of halloysite nanotubes (HNT) was decorated onto bamboo pulp fibers through layer-by-layer assembling of chitosan (CS) and phytic acid (PA). This modification retained the highly porous microcellular structure of the resultant BPF (92 %–98 %). It improved its compressive strength by 228.01 % at 50 % strain, endowing this foam with desired thermal insulation properties and sound absorption coefficient comparable to commercial products. More importantly, this foam possessed exceptional flame retardancy (47.05 % reduction in the total heat release and 95.24 % reduction in the total smoke production) in cone calorimetry, and it showed excellent extinguishing performance, indicating considerably enhanced fire safety. These encouraging results suggest that the flame retardant BPF has the potential to serve as a renewable and cost-effective alternative to traditional foam for applications in acoustic and thermal insulation.

Thermal Conductivity of CaSrFe2O6-δ

The thermal conductivity of CaSrFe2O6-δ, an oxygen-deficient perovskite, is a critical parameter for understanding its thermal transport properties and potential applications in energy conversion and electronic devices. In this study, we present an investigation of the thermal conductivity of CaSrFe2O6-δ at room temperature for its thermal insulation property study. Experimental measurement was conducted using a state-of-the-art thermal characterization technique, Thermtest thermal conductivity meter. The thermal conductivity of CaSrFe2O6-δ was found to be 0.574W/m/K, exhibiting a notable thermal insulation property.

Tunable gas absorption capability for graphene doped silica aerogel by wrinkle structure: Effects of gas absorption, mechanical properties and thermal insulation

Gas absorption capability of material proposes a dominant role in the energy storage, selective gas absorption/capture. Aerogels with ultra-high porosity, ultra-low thermal conductivity have been widely used in gas absorption. However, a persistent limitation of these materials is their static and unalterable gas absorption capacity. In this work, a wrinkled graphene structure is proposed to adjust the gas capability. A series of molecular dynamics (MD) simulations are carried out to propose an atomic-level understanding of the effects of wrinkled structure, including effects of pressure, surface wettability, number of gas molecules, thermal insulation, and mechanical properties. It is found that the gas capability can be reduced by 20% with wrinkle structure. Notably, the linear response between pressure and gas absorption capability is observed. Moreover, wrinkle structure functions as a thermal resistance to restrict solid heat transfer. The mechanical property of the aerogel composite is improved by a doped graphene sheet with a high wrinkle degree. This work will pave the way for the development of aerogel with high and selective gas absorption capability.