Insulation Materials Research Articles

Study on the Space Charge Characteristics of Polypropylene Insulation Material Under a Polarity Reversal Electric Field

High-voltage (HV) cables may experience voltage polarity reversal during power adjustment, leading to the accumulation of space charges inside the insulation material and causing distortion of the internal electric field. To characterize the effect of grafting modification on the insulation properties of polypropylene (PP), various electrical properties were characterized. The results show that grafting modification can significantly improve the electrical properties of PP, with PPG-2 exhibiting the best electrical properties. Compared with PP, the breakdown strength of PPG-2 is increased by 39.27%, and the critical electric field is increased by 36.52%. Meanwhile, the charge accumulation inside the PPG-2 is extremely small after voltage polarity reversal. The mechanism of grafting modification to enhance the electrical properties of PP was explained by analyzing the trap characteristics of the samples. This indicates that grafting modification introduces a large number of deep traps within PP, suppressing the injection and migration of charge carriers. The presence of deep traps weakens the charge accumulation and electric field distortion at the interface. In this paper, the optimal monomer and content of grafted PP were determined, and the insulation properties of the cable under operating conditions were analyzed. The research results offer practical guidance for the development of high-performance grafted PP cable insulation materials and the reliability of cable operation.

Characteristics of Polybenzoxazine Aerogels as Thermal Insulation and Flame-Retardant Materials

Polybenzoxazine-based aerogels are a unique class of materials that combine the desirable properties of aerogels—such as low density, high porosity, and excellent thermal insulation—with the outstanding characteristics of polybenzoxazines—such as high thermal stability, low water absorption, and superior mechanical strength. Polybenzoxazines are a type of thermosetting polymer derived from benzoxazine monomers. Several features of polybenzoxazines can be retained within the aerogels synthesized through them. The excellent thermal resistance of polybenzoxazines, which can withstand temperatures above 200–300 °C, makes their aerogel able to withstand extreme thermal environments. The inherent structure of polybenzoxazines, rich in aromatic rings and nitrogen and oxygen atoms, imparts flame-retardant property. Their highly crosslinked structure provides excellent resistance to solvents, acids, and bases. Above all, through their molecular design flexibility, their physical, mechanical, and thermal properties can be tubed to suit specific applications. In this review, the synthesis of polybenzoxazine aerogels, including various steps such as monomer synthesis, gel formation, solvent exchange and drying, and finally curing are discussed in detail. The application of these aerogels in thermal insulation and flame-retardant materials is given importance. The challenges and future prospects of further enhancing their properties and expanding their utility are also summarized.

Low-temperature growth of wafer-scale amorphous boron nitride films with low-dielectric-constant and controllable thicknesses.

Amorphous boron nitride (aBN) films, with extremely low relative dielectric constant (κ) and chemical inertness, are excellent insulation and packaging materials for electronic device interconnection. It is of great significance to prepare the low-κ aBN films with controllable thickness, but there are still some limitations to achieve the goal. In this study, we succeed in growing wafer-scale aBN films with specific thicknesses from 1.2 to 4.0 nm by varying the growth time and temperature. The thickness of the films increases linearly with growth time and the crystallinity of BN films is precisely controlled by the growth temperature. The preferred temperature for aBN films ranges from 200 to 400 °C. Raman spectroscopy, X-ray photoelectron spectroscopy and transmission electron microscope all confirm the amorphous feature. These films are wafer-scale uniformity and have an ultra-flat surface, with excellent thermal stability and corrosion resistance. Particularly, the growth temperature affects the κ value and breakdown voltage of aBN films. The aBN films grown at 200 °C have the lowest κ value of 1.66 at 100 kHz, along with the breakdown field strength of 5.5 MV/cm. We believe that wafer-level aBN films with various thicknesses can bring new opportunities for the development and application of nanoscale electrical devices.

Thermal and acoustic properties of lime‐based sustainable insulation materials produced from hemp fibers modified with boron

AbstractThe importance of using natural materials in the construction field within the framework of sustainable and environmentally friendly approaches is increasing day by day. In this context, this study was aimed to develop a hemp fiber‐based insulating building material. The boron doped fibers were characterized by thermogravimetric and differential thermal analysis (DTA/TGA) and field emission environmental scanning electron microscopy (FE‐ESEM). The materials were produced by mixing undoped, 10% and 15% boric acid doped hemp fibers separately with lime. The fiber:binder ratio was determined as 1:4 by weight in all samples. To determine the thermal and acoustic properties of the produced samples; thermal conductivity test with heat flow plate method, sound absorption and sound transmission loss tests with impedance tube method were carried out. In order to determine the mechanical strength of the materials, a three‐point bending tests were performed. As a result of the analyses, the thermal conductivity coefficients of the samples produced using hemp fibers, which are undoped, doped with 10% and 15% boric acid solution, were determined as 0.0935, 0.1926, and 0.1863 W/mK, respectively; noise reduction coefficients (NRCs) were measured as 0.425, 0.443, and 0.385, respectively; the highest sound transmission loss values were recorded as 27.17, 33.50, and 46.92 dB, respectively; and the flexural strength (σf) values were determined as 1.922, 1.992, and 2.578 MPa, respectively.

Effect of climate change on hygrothermal performance of timber framed wall with different insulation materials

Effect of climate change on hygrothermal performance of timber framed wall with different insulation materials

Ultrasonic sprayed hollow ceramic/carbon microspheres function as thermal insulation, ablative resistance, and electromagnetic shielding materials

Ultrasonic sprayed hollow ceramic/carbon microspheres function as thermal insulation, ablative resistance, and electromagnetic shielding materials

Study on the change of the oil-paper insulation’s AC conductivity characteristics based on dielectric response in frequency domain

Oil-immersed power equipment (transformers and high voltage bushings) are key components of power systems. Oil-paper insulation has endured complex and harsh operating conditions when used as a primary insulation system, so it is essential to determine the insulation state of oil-paper insulation system to ensure a stable operation for the power grid. The oil-paper insulation’s conductivity behavior can effectively characterize the degree of insulation deterioration. However, the relationship between the alternating current (AC) and direct current (DC) conductivity behavior for oil-paper insulation systems is still unclear in current research, resulting in limitations in the traditional evaluation model’s application. Therefore, this paper uses oil-paper insulation materials under different aging to carry out relevant research about the changing features of the complex AC conductivity under different test temperature environments. The influence of oil-paper insulation aging, test temperature, and excitation frequency on the complex AC conductivity is verified. Considering the correlation between low-frequency AC conductivity and DC conductivity, the frequency range of AC conductivity is extended by means of frequency temperature and conductance double translation. The temperature dependence of the AC conductivity behavior is defined over a wide frequency test range. The relaxation polarization process dominated the AC conductivity variation law is obtained. The impact of experimental temperature and insulation aging on the cumulative characteristic parameters of AC ionic mobility is clarified. This study theoretically corrects the traditional calculation model for AC conductivity of oil-paper insulation. The bias in conductivity calculations caused by only considering a single relaxation polarization process is eliminated. The conductivity model that can characterize multiple relaxation polarization processes in the dielectric is established. This model provides theoretical support for the later assessment of oil-paper insulation state depending on conductance behavior.

A Numerical Model for Predicting the Smoldering Behavior of Bio-based Insulation Materials: Model Theory and Validation

A Numerical Model for Predicting the Smoldering Behavior of Bio-based Insulation Materials: Model Theory and Validation

Electrical Aging of Fluoropolymer Cable Insulation Materials Induced by Partial Discharge

Electrical Aging of Fluoropolymer Cable Insulation Materials Induced by Partial Discharge

Valorising End-of-Life Mattress Waste into Sustainable Construction Insulation Materials

Valorising End-of-Life Mattress Waste into Sustainable Construction Insulation Materials

Direct Assembly of Grooved Micro/Nanofibrous Aerogel for High-Performance Thermal Insulation via Electrospinning.

Maintaining human body temperature in both high and low-temperature environments is fundamental to human survival, necessitating high-performance thermal insulation materials to prevent heat exchange with the external environment. Currently, most fibrous thermal insulation materials are characterized by large weight, suboptimal thermal insulation, and inferior mechanical and waterproof performance, thereby limiting their effectiveness in providing thermal protection for the human body. In this study, lightweight, waterproof, mechanically robust, and thermal insulating polyamide-imide (PAI) grooved micro/nanofibrous aerogels were efficiently and directly assembled by electrospinning. The grooved micro/nanofibrous aerogels were directly prepared by controlling the relative humidity and solvent evaporation rate, as well as regulating the charge jet density and phase separation behavior. The prepared aerogel exhibited ultralight performance with a density of 4.4 mg cm-3, hydrophobic liquid-repelling performance with a contact angle of 137.4°, and ultralow thermal conductivity (0.02586 W m-1 k-1), making it an ideal material for maintaining thermal comfort in complex environments. This work provides valuable insights into the design and development of high-performance fiber insulation materials.

Evaluating environmental impacts of bio-based insulation materials through scenario-based and dynamic life cycle assessment

Abstract Purpose Bio-based insulation materials can have a significant impact in achieving net zero target in the construction sector. However, they face challenges due to lack of data on environmental performances and professional perception, hindering their proliferation. This study aims to combine scenario-based and dynamic analyses of environmental performances to provide comprehensive environmental information on bio-based thermal insulation materials. The goal is to empower professionals with robust information, facilitating informed decisions and promoting the selection of bio-based materials. Methods Data on manufacturing, use, recyclability, and technical performance of eleven commercially available natural insulation materials were collected from the literature to create a Life Cycle Inventory (LCI). For each material, a scenario-based life cycle assessment (LCA) was conducted by modelling variation in manufacturing, transportation, end-of-life and material properties, using the UK as the primary case study. Materials were compared to three non-bio-based insulation materials by ranking the thirteen environmental impact categories in EN 15804(2013) + A2(2019) to give an exhaustive overview of their potential benefits and burdens. Additionally, a dynamic LCIA was performed to implement in the analysis both short-and long-term emissions, exploring the impact of biogenic carbon. Results The scenario analysis highlighted that recycled cotton and hemp fibre insulation have the lowest impact across all impact categories, attributed to their sustainable manufacturing processes and minimal impacts at the end-of-life stage. The dynamic LCIA demonstrated that recycled textile insulation has the lowest impact both in the short-term (prior to waste disposal) and the long-term (post-waste disposal), regardless of the chosen end-of-life scenario. Furthermore, it indicated that cotton and hemp fibre have a negligible impact on global temperature changes, achieving a net-zero effect in the short-term and close-to-zero impact in the long-term. Conclusion The novelty of this paper lies in its comprehensive investigation of the environmental impacts of bio-based thermal insulation materials, employing multiple tools to enhance generalizability. These results will support decision-making by providing data ranges to help practitioners identify the most environmentally friendly insulation materials. Additionally, they offer insights into how similar products compare within that range, driving progress in the built environment towards net-zero emissions. Whilst the full dataset and evaluation methods are illustrated through a UK-based case study, this method can be adapted for specific scenarios and projects, due to the transparency of data and methods. This research significantly influences the built environment and promotes net-zero targets within the sector.

Energy-Efficient Insulating Geopolymer Foams with the Addition of Phase Change Materials.

This study assessed the impact of the addition of phase change materials (PCMs) under the trade name Micronal 28S on the properties of the manufactured geopolymer foams. Micronal 28S is used as a functional component in foams (insulation materials), foamed building materials, and materials for temperature regulation to improve thermal comfort and indoor climate. The melting point of Micronal 28S is 28 ± 2 °C, and the heat of fusion is ∼140 J/g. As part of the research, geopolymer mixtures containing PCMs in the form of a slurry were prepared in shares of 0, 5, 10, and 15 wt %. Geopolymers were produced based on fly ash. The foaming process was carried out using hydrogen peroxide (H2O2). Physical, mechanical, and thermal properties and analysis of the microscopic microstructure were evaluated. The introduction of Micronal 28S into the geopolymer matrix is conducive to obtaining ultralight foams with a density of about 200 kg/m3. As the share of the PCM increases, the thermal insulating properties of the samples increase by reaching a thermal conductivity coefficient λ of 0.057 W/m*K. Simultaneously, the specific heat increases up to 1.105 kJ/kg*K. Microstructure analysis confirmed that Micronal 28S tends to agglomerate and decrease pore size. The phase change material reduces the mechanical properties of the geopolymers. However, according to the EN 998-1 standard, the conditions for the requirements to be realized by insulating materials used in construction were met by a reference sample and one containing 5 wt % of Micronal 28S. The content in this publication addresses issues in both materials science and mechanical engineering. Although other authors have conducted research using various phase change materials, this work is the first to use PCMs with the trade name Micronal 28S to produce geopolymer foams with excellent thermal insulation properties.

Elucidating Mesostructural Effects on Thermal Conductivity for Enhanced Insulation Applications.

Thermal management is a key link in improving energy utilization and preparing insulation materials with excellent performance is the core technological issue. Complex and irregular pore structures of insulation materials hinder the exploration of structure-property relationships and the further promotion of material performance. Ordered mesoporous silica (OMS) is a kind of porous material with ordered frameworks. This work elucidates the effects of ordered porous architecture on the thermal conductivity of mesoporous silica. Herein, two typical OMS, SBA-15 and SBA-16, characterized by well-defined porous structures with distinct spatial orientations are synthesized to study the relevance between structure and thermal conductivity. Compared to the 3D cubic mesoporous structure of SBA-16, the 2D hexagonal structure of SBA-15 exhibits anisotropic effects that restrict both solid and gaseous conduction, thereby providing better thermal insulating. Due to the influence of porosity, the thermal conductivity is found to decrease strongly with increasing pore size and decreasing wall thickness. Moreover, OMS composite aerogels with outstanding thermal insulation, mechanical performance, and hydrophobicity are fabricated through incorporating OMS into cellulose nanofibers (CNF). Consequently, this work contributes to a deeper understanding of heat transfer in OMS and provides an idea for designing OMS-based composite materials, thereby advancing their potential applications.

Design of Perlite Based Thermal Insulation Plate and Determination of its Physical, Mechanical and Thermal Properties

According to the current fire regulations in Turkey, the use of insulation materials such as EPS, which are commonly employed in building insulation, is limited to buildings up to 28.5 m in height. The regulations mandate the use of Class A fire-resistant thermal insulation materials in high-rise buildings. However, these materials may present challenges in terms of application and sustainability. This study aims to develop a perlite-based thermal insulation board that is Class A fire-resistant, competitive with traditional insulation materials, and possesses optimal physical, mechanical, and thermal properties. In the production of the specimens, expanded perlite, liquid sodium silicate, and silicon powder were used, and tests for apparent density, compressive-flexural strength, capillary water absorption, and thermal conductivity were conducted in accordance with EN standards. In the first stage, the produced specimens were subjected to four different activation temperatures to determine the optimal process temperature. In the second stage, the ratios of perlite, sodium silicate, and water were varied to achieve the mixture design that yielded the highest mechanical properties from the specimens. In the final stage, water-repellent admixtures were incorporated into the batches at mass ratios of 1.5 %, 3 %, 4.5 %, and 6 %. The perlite-based thermal insulation board, which offers optimal properties in the most cost-effective manner, has an apparent density of 127 kg·m−3, compressive strength of 266 kPa, flexural strength of 156 kPa, capillary water absorption value of 0.0197 kg·m−2·min−0.5, thermal conductivity of 0.0475 Wm−1·K−1, and a unit cost of 97 $ m−3. Consequently, the insulation board developed in this study presents a viable alternative to conventional insulation materials, offering Class A fire resistance.

Lightweight Natural Fiber Insulation Boards Produced with Kapok Fiber (Ceiba Pentandra) and Polylactic Acid or Bicomponent Fiber as a Binder

AbstractTraditionally, kapok fiber is employed as filling for soft pillows, bedding, and diverse elements. Due to its buoyancy and proportion between cell wall and lumen, it is also applied as buoyant material in life vests and insulation materials. This study examine slightweight insulation panels produced from kapok fibers. Lightweight insulation boards are produced by hot‐air using kapok fibers (95%) bonded with polylactic acid or bicomponent fiber (5%), achieving very low densities of 10,15, and 20 kg.m−3. The technological attributes like density, porosity, water absorption, wettability, compression, and thermal conductivity, are evaluated against commercial glass wool. In terms of water absorption rates, there is a direct correlation with density. All the variables reach short‐term water absorption values less than 1 kg.m−2, which are comparable to commercial standards. This can be attributed to the lower density, higher porosity of the samples, and the inherent hydrophobic wax layer in the cell wall surface of kapok fibers. This trend is also evident in wettability tests, where produced boards demonstrated water‐repellency when exposed to water. Regarding the mechanical property of compression, neither the binder nor the density significantly impacts compression strength. The thermal conductivity performance of kapok‐based boards is comparable with commercially available ones.

Green building development utilising modified fired clay bricks and eggshell waste

The inadequate thermal insulation of the building envelope contributes significantly to the high power consumption of air conditioners in houses. A crucial factor in raising a building’s energy efficiency involves utilizing bricks with high thermal resistance. This issue is accompanied by another critical challenge: recycling and disposing of waste in a way that is both economically and environmentally beneficial, including using it to fuel industrial growth, in order to reduce the harmful effects of waste on the environment as waste generation in our societies grows. To this end, the current study sought to assess whether integrating a specific amount of eggshell waste as CaCO3 filler within bricks consistently produces fired clay bricks with desirable thermal insulation capabilities. By systematically investigating the physicochemical and thermal characteristics of bricks doped with varying eggshell content, this work demonstrates how waste materials can be repurposed to produce sustainable construction materials with superior performance. The results highlight significant improvements in thermal conductivity, diffusivity, and effusivity, alongside favorable changes in porosity, bulk density, and mechanical strength. The XRD analysis revealed that once the firing temperature rises, a high insulation feature arises due to siliceous melt formation. EDX analysis gave important insights into the impact of eggshell dopants on the physicochemical parameters of burnt clay bricks. Compared to pristine brick, CEs7% brick constructed with clay and 7 wt% eggshell exhibited a 38.7% loss on dry shrinkage, an enhancement on average pore size of 78.8%, an apparent porosity of 52.7%, a bulk density of 8.3%, and a compressive strength of 57.5%. The reduced shrinkage enhances stability, while increased pore size and porosity improve thermal insulation, making the bricks more durable and energy-efficient. In this regard, the brick containing 10% eggshell that was fired at 1100°C possessed the greatest drop in heat conductivity (i.e., 50%), thermal diffusivity (30%), and thermal effusivity (30%) as compared to the pure one. Given the aforementioned findings, these additions hold the potential to reduce the energy required for both heating and cooling buildings. This brings us to the conclusion that combining eggshell waste to create calcium silicate makes it feasible to be utilized as a thermal insulation material, paving the way for improved construction materials’ performance and sustainability.

Preparation and corrosion resistance to cathode materials for lithium‐ion batteries of CA6 foam ceramics

AbstractCA6 foam ceramics (CA6‐FCs) with CA6 as the main crystalline phase were prepared by adding CA6 powder through gel casting process, which reduced the severe shrinkage in the reaction synthesis process of CA6. This simple preparation process can realize the industrial production of CA6‐FCs. The linear change and physical properties of CA6‐FCs can be controlled by adjusting the additional amount of CA6 powder and the solid content of the slurry. The corrosion resistance of CA6‐FCs is better than that of the current mainstream mullite thermal insulation materials in lithium‐ion battery cathode materials. Through the simple process of this study, on the basis of industrial production, CA6‐FCs can replace mullite lightweight thermal insulation materials to improve the alkali corrosion resistance, service life, and maintain production safety of kiln lining.

Theoretical Modelling, Experimental Testing and Simulation Analysis of Thermal Properties for Green Building-Insulation Materials

In this study, 45 alternative green materials for building walls were experimentally produced, utilizing renewable (epoxidized sesame oil), natural (clay), and waste (Seyitömer fly ash) resources. These materials were evaluated based on key technical properties such as mass, tensile-compressive strength, and thermal conductivity, all of which are essential for construction and insulation applications. Subsequently, theoretical modeling was conducted for the material coded SE45, which demonstrated the lowest thermal conductivity. Through mathematical calculations, the theoretical thermal conductivity value was determined with a deviation of +5.88%. Furthermore, 48 alternative scenarios were designed for three different building envelope types (internally insulated, externally insulated, and sandwich), using commonly used building insulation materials alongside the sesame oil-based green material with the lowest thermal conductivity (SE45). Energy performance evaluations were conducted by analyzing temperature distributions along the walls of all designed scenarios using ANSYS simulations under the climatic conditions of Ankara, Turkey.

Thermal Insulating and Mechanically Strong Polyimide Aerogel Composites Reinforced by Polyhedral Oligomeric Silsesquioxane-Grafted Carbon Nanotubes

In the ship industry, developing thermal insulation materials with exceptional high-temperature resistance, structural stability and light weight is essential. Herein, polyimide (PI) composite aerogels were synthesized. Carbon nanotubes (CNTs) introduced cross-linking structures within the aerogel matrix, effectively reducing shrinkage and forming micrometer-scale pores. Furthermore, the rigid cage-like structure of polyhedral oligomeric silsesquioxane (POSS) generated additional nanoscale pores. This multiscale pore structure enhanced both compressive strength and thermal insulation properties. The PI-CNT-POSS composite aerogel with a 2 wt% CNT content (PI-CP2) demonstrated outstanding overall performance, with compressive strength, modulus and thermal conductivity values of 167.7 KPa, 360.3 Kpa and 40.6 mW/(m·K), respectively, possessing remarkable advantages over the neat PI aerogel. Consequently, this PI composite aerogel can be used as a promising material for heat management in complex environments.