Heat-insulating Materials Research Articles

Processing of Pinus sylvestris L. into a heat-insulating, thermally stable, and flame-retarded material by combining the flame-retardant impregnation and densification treatment

Abstract Flame-retardant impregnation and densification are two major modification techniques to improve the fire safety of wood. Here, these two techniques were combined to prepare flame-retarded wood, aiming at further fire hazard reduction. The delignated Pinus sylvestris L. was impregnated with boric acid (BA) and graphene oxide (GO) solutions, then densified to prepare densified flame-retarded wood named BGO-DW sample. The results revealed that the BGO-DW sample obtained a limiting oxygen index (LOI) value of 47.4 %. Its backside temperature after 1200 s heating was 49 % lower than that of unmodified wood. Besides, the peak heat release rate (PHRR) and total heat release (THR) values of BGO-DW sample were 72 and 62 % lower than those of unmodified wood due to its shorter pyrolysis interval and lower peak mass loss rate (PMLR), as supported by thermogravimetric (TG) analysis. The flame retardancy of BGO-DW sample could be attributed to the formation of compatible char containing C=C aromatic structure, C–O–C cross-linked structure, and boron trioxide (B2O3) structure. These features of BGO-DW sample offer a new method to improve thermal stability, heat insulation, and flame retardancy for wood and wood-based products.

Heat insulating jute-reinforced recycled polyethylene and polypropylene bio-composites for energy conservation in buildings

The development of jute-reinforced recycled polyethylene (PE) and polypropylene (PP) bio-composites using a heat-pressed molding technique and the feasibility of using them as thermal-insulating panels in building interiors have been studied in the current research. Lignocellulosic natural jute fibers of different volume fractions were employed as reinforcement to fabricate recycled PP and PE composites, and their thermal and mechanical characteristics were investigated for the intended applications. The developed jute-PP composites showed a higher tensile (75.16 MPa) and flexural (121.13 MPa) strength compared to jute-PE with the tensile and flexural strength of 55.62 MPa and 74.53 MPa, respectively, which is attributed to the better tensile strength of PP and its superior interfacial bonding with the jute fiber than PE. The fractographic investigation also confirmed the desired interfacial attachment of reinforcement and recycled polymers in the composite structure. The heat barrier characteristics, including low thermal conductivity (0.2694 W/m.K and 0.1852 W/m.K for jute-PE and jute-PP, respectively) and enhanced conductive and radiative heat resistance with increased volume fraction of jute fiber, specified adequate heat barrier performance of the developed composites for building thermal applications. The thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) study revealed comparable thermal stability of both composites at elevated temperatures. Additionally, due to reduced interfacial vacuity and the existence of hydrophobic PE and PP, composite samples demonstrated very low water absorption with time, which suggested the potentiality of utilizing them as durable heat-insulating materials in building structures. Accordingly, the fabrication of thermal-insulating engineered recycled biocomposites and their application in designing green buildings can significantly contribute to reducing the global carbon footprint associated with thermal energy consumption of buildings and alleviating the growing environmental problems of plastic waste by utilizing them as matrix polymer in fiber-reinforced composites.

One-Pot Sol-Gel Synthesis of Highly Insulative Hybrid P(AAm-CO-AAc)-Silica Aerogels with Improved Mechanical and Thermal Properties.

Silica aerogels and their derivatives have outstanding thermal properties with exceptional values in the thermal insulation industry. However, their brittle nature restricts their large-scale commercialization. Thus, enhancing their mechanical strength without affecting their thermal insulating properties is essential. Therefore, for the first time, highly thermally stable poly(acrylamide-co-acrylic acid) partial sodium salt is used as a reinforcing polymer to synthesize hybrid P(AAm-CO-AAc)-silica aerogels via epoxy ring-opening polymerization in the present study. Functional groups in P(AAm-CO-AAc) partial sodium salts, such as CONH2 and COOH, acted as nucleophiles for the epoxy ring-opening reaction with (3-glycidyloxypropyl)trimethoxysilane, which resulted in a seven-fold enhancement in mechanical strength compared to that of pristine silica aerogel while maintaining thermal conductivity at less than 30.6 mW/mK and porosity of more than 93.68%. Moreover, the hybrid P(AAm-CO-AAc)-silica aerogel demonstrated improved thermal stability up to 343 °C, owing to the synergetic effect between the P(AAm-CO-AAc) and the silica aerogel, corresponding to the thermal stability and strong covalent bonding among them. These excellent results illustrate that this new synthetic approach for producing hybrid P(AAm-CO-AAc)-silica aerogels is useful for enhancing the mechanical strength of pristine silica aerogel without impairing its thermal insulating property and shows potential as an industrial heat insulation material.

DETERMINATION OF THE CHEMICAL AND MINERALOGICAL COMPOSITION OF TRACHIBASALTIC PORPHIRITE FROM THE GAVASAY FOR OBTAINING MINERAL FIBER

The results of studies of the chemical and mineralogical compositions and the main characteristics for determining the suitability of trachybasaltic porphyrite from the Gavasay deposit of Uzbekistan for obtaining heat-insulating material, in particular mineral fiber, are presented. It has been established that this new deposit of igneous rock can be used as the main raw material component for the production of basalt fiber products, a widely demanded and modern material in the construction industry.

The Fire Resistance of Transformable Barriers: Influence of the Large-Scale Factor

The paper presents the results of the development of a multi-layer protective product, which is a transformable fire barrier, installed in buildings and structures to limit the spread of flame, heat flow and smoke. Based on the results of the simulation of eight samples of fire curtains, three promising samples of different compositions were selected, demonstrating a fire resistance limit on the loss of thermal insulating capacity (I) of 30 min. During the small-scale tests, it was found that the multilayer fabric of the following composition was promising: heat-treated silica fabric, aluminum foil, mineral fiber heat insulation material, stitched by needle-punching with silica thread, fabric reinforced with fiberglass mesh and stitched through with basalt thread, with seams treated with a fire-resistant elastic sealant. According to the results of a standard large-scale experimental study, a fire curtain with a loss of integrity not less than 60 min, and a loss of thermal insulating ability not less than 15 min were obtained. The results of the study assess the impact of the scale factor on the fire resistance limit of fire curtains in a fire.

Synergistic Effects between Multiphase Thermal Insulation Functional Phases on the Mechanical and Heat Insulation Properties of Silicone Rubber Composites.

This work utilizes the synergistic effect between three different functional phases of thermal insulation, i.e., hollow ceramic microspheres (HCMs), hollow silica microspheres (HSMs), and hydroxy silicone oil blowing agent, to prepare a flexible and efficient thermal insulation composite with low thermal conductivity and high structural strength. First, the effects of the three phases on the mechanical and thermomechanical properties of silicon rubber (SR) were analyzed using a scanning electron microscope (SEM), a thermogravimetric (TG) analyzer, a thermal conductivity meter, and a universal testing machine, respectively. Then, the thermal insulation mechanism of multiphase thermal insulation composite materials was analyzed. The results show that the thermal stability and mechanical performance of composites were significantly enhanced, particularly for sample 18H, whose Tmax and char yield reached 621.3 °C and 77.5%, respectively, representing a respective increase of 12.1 and 35.3% compared to those of pure SR. After heat treatment at 1000 °C, the linear shrinkage of the sample diameter was about 9.4%, while the thermal conductivity was as low as 0.064 W/(m·K), which was 53.2% lower than that of the pure matrix SR. We believe that this work can serve as a reference for the preparation of heat insulation and protection materials with low thermal conductivity and high structural strength.

Wastes from the production of heat-insulating basalt wool as an additive in cement-based materials

The building materials science at the present stage is aimed at expanding the components of composites. At the same time, these components acquire special value with the simultaneous disposal of various wastes. One of such materials that have not been studied before are molten spherical basalt particles (beads) formed as waste in the production of heat-insulating materials. The aim of the article was to study the effect of balls on the structure formation of cement materials. The vibration spectra of basalt balls, which differ from the spectra of pure silica, were studied, which makes it possible to form silicates with different contents of aluminum and iron. The revealed features of the particle surface morphology, grain composition and the presence of amorphous silicate phases in this material confirm its effective use as an active mineral additive in cement concretes of normal and autoclaved hardening. The activity of this binder component is confirmed by the fact that after 180 min 15 mg/g calcium hydroxide is absorbed. SEM images confirmed compaction of the microstructure of cement composites containing crushed basalt granules. As a result of the use of this new additive, the compressive strength increases, while the maximum effect is achieved when 5–10% of finely ground basalt balls are introduced into the mixture. Amorphous quartz accelerates the pozzolanic reaction, increasing the packing density of hydration products. These basalt granules are able to accumulate water, which then takes part in the hydration reaction in a dosed manner. The increased water-holding capacity of the created binder creates conditions for the consistent growth of hydrated products and for synthesis with minimal internal stresses and volumetric deformations.

Design of Aerospace Vehicles’ Thermal Protection Based on Heat-Insulating Materials with Optimal Structure

Highly porous open-cell carbon materials have great potential for use as high-temperature thermal insulation for space vehicles due to a unique combination of properties: low density, high rigidity, sufficient compressive strength, and low thermal conductivity. The physical properties of these materials essentially depend on their microstructure. This implies the possibility of constructing a new advanced technique for the optimal design of multilayer thermal protection systems for aerospace vehicles, taking into account the dependence of materials’ thermal properties on microstructure. The formulation of the optimization problem traditional to thermal design implies the determination of the layer thicknesses that provide a minimum specific mass of the thermal protection, subject to the specified constraints on the maximum temperatures in the layers. The novelty of this work lies in the fact that, along with the thickness of the layers, the design parameters include the cell diameter and porosity, which characterize the structure of highly porous cellular materials. The innovative part of the presented paper lies in the determination of cell diameter and the porosity of open-cell carbon foam together with the thickness of the layers for multilayer thermal insulation, ensuring the required operational temperature on the boundaries of the layers and a minimum of the total mass of the system. This article reveals new possibilities for using the numerical optimization method to determine the geometric parameters of the thermal protection system and the morphology of the materials used. A new methodology for designing heat-loaded structures based on the simultaneous selection of macro- and micro-parameters of the system is proposed. The basic principles of constructing an algorithm for designing a multilayer thermal protection system are outlined, taking into account the possibility of choosing the parameters of the highly porous materials’ structure. The reliability of the developed optimization method was verified by comparing the results of mathematical modeling with experimental data obtained for highly porous cellular materials with known microstructure parameters.

Evaluation of thermal insulation of pipelines in the overhead method of laying in the climatic conditions of the South of Russia

The characteristics of used and new heat-insulating materials for pipelines of heating networks are presented. Functions have been established for determining the outer diameter of a pipeline with thermal insulation for all materials under consideration. A two-factor machine experiment was carried out, as a result of which the quantitative dependence of specific heat losses on the thermal conductivity coefficient and pipeline diameter was determined. Graphical interpretations of the obtained functions are presented. Based on the analysis of the obtained results, it was established which factor has the greatest influence on the value of specific heat losses and which heat-insulating material should be used.

Manufacturing Technologies of Flexible Heat-Insulating Materials: Review

Manufacturing Technologies of Flexible Heat-Insulating Materials: Review

Determination of the Optimal Gas-forming System Used to Obtain Low-density Foamed Material

The most effective gas-forming system used to obtain low-density foaming material is considered. During the discussion, the advantages and disadvantages of the raw materials used were identified, and their impact on the production of foam and material properties were considered. A complex of general scientific research methods was used, based on the theoretical analysis of technological solutions for the production of foamed material, described in the scientific and technical literature, patents, as well as scientific articles. The purpose of the article is to identify an effective gas – forming system used in the production of environmentally safe low-density foaming material suitable for use as a heat-insulating material in construction. When conducting scientific research, standard measuring instruments and differential scanning calorimetry, laser diffraction and modern testing equipment for methods of analyzing the physico-mechanical properties of foamed inorganic materials were used.

УДОСКОНАЛЕННЯ КОНСТРУКЦІЇ ВОДООХОЛОДЖУВАНИХ ПАНЕЛЕЙ ДУГОВИХ СТАЛЕПЛАВИЛЬНИХ ПЕЧЕЙ ЛИВАРНОГО КЛАСУ

The article outlines the importance of the foundry industry and the role of arc steelmaking furnaces (ASFs) in it. It was noted that water-cooled panels in EAFs are key elements that ensure the structural integrity and safety of furnaces by removing excess heat during steelmaking. An analysis of literature sources has revealed that there are certain issues that characterize the imperfections of certain structural parts of modern water-cooled panels, such as insufficient cooling efficiency, corrosion, and leaks, which lead to a decrease in the performance of the BF and an increase in energy consumption. These factors have been analyzed and some optimization ways have been identified to improve overall efficiency and durability. The article emphasizes that modern technologies can reduce the consumption of energy and refractory materials by reducing the capacity of the steelmaking bath and optimizing the heat balance. Particular emphasis is placed on the potential for modernizing water-cooled panels to improve the efficiency of the steelmaking process. The paper reveals the mechanism of operation of water-cooled chipboard panels as a spatial system of steel tubes connected by means of transition elements and placed with different densities and a layer of thermal insulation material in the intertube space. This determined the need to improve the design of the panels by optimizing their spatial structure to ensure a more efficient heat transfer process. Improving the energy efficiency of chipboard means reducing heat energy losses, which, among other things, ensures more stable operation during melting, reduces component wear and extends the service life of water-cooled panels. The design of the water-cooled panels has been improved by varying the distance between the axes of the water-cooled tubes depending on their diameter and spatial location. This design makes it possible to optimize the layer of heat-insulating material and minimize unproductive heat loss. Failure to comply with the calculated value of the pipe spacing can lead to increased heat loss. The calculations and graphical dependencies demonstrate the efficiency of heat flow distribution and minimization of heat losses. The new design reduces heat loss by 45% and improves the performance of water-cooled panels.

Thermal efficiency analysis of the rotary kiln based on the wear of the lining

The thickness of the lining is reduced from 230 mm to 80 mm due to long-term wear, resulting in low thermal efficiency of the rotary kiln. The thermal resistance, which is positively correlated with the thickness of the lining, is one of the most important factors determining the thermal efficiency of the rotary kiln. The thermal efficiency of the rotary kiln can be improved by introducing insulation material with lower thermal conductivity into the lining. The average heat flux is used as the thermal efficiency evaluation index of the 4×60 m rotary kiln under no-load conditions in this work. A numerical experiment was conducted for the temperature and heat flux of the inner surface of the lining, as well as the temperature of the outer surface of the shell during the wear of the lining. There are two cases considered, one with and one without insulation materials in lining. According to the analysis, when the lining in the high temperature zone of the rotary kiln wears to 80 mm, the average heat flux of the inner surface of the lining increases by 105.03%. However, after the addition of insulation material, the average heat flux on the inner surface of the lining increases by 40.38% (wears to 80 mm). Compared to the thermal efficiency of the rotary kiln without heat insulation material, the average heat flux of the inner surface of the lining is reduced by 36.36% (230 mm), and it is reduced by 99.01% (wears to 80 mm). A significant advantage of this solution is that it can increase the thermal efficiency of the rotary kiln, improve the insulation performance of the lining, reduce heat loss to the environment through the shell, and the results obtained can be used for the latest equipment design and existing equipment improvements.

A Novel Inner Wall Coating-Insulated Oil Pipeline for Scale and Wax Prevention

During the production of deep oil and gas, scaling, waxing, hydrate ice plugging and other problems easily occur. To solve these problems, reducing the temperature loss of oil pipelines is a feasible method. In order to protect the outer wall coating from being damaged and losing its thermal insulation performance, this paper proposes a developed technology for a novel inner wall coating-insulated oil pipeline. A new temperature-resistant and heat-insulating material aerogel was optimized and developed, and it has an extremely low thermal conductivity of less than 0.055 W/m·K. The influence of different coating processes on the thermal insulation coefficient was analyzed, and a novel inner wall coating-insulated oil pipeline was developed. A testing and evaluation platform for its thermal insulation effect was built, and a finite element model was established to analyze the temperature field distribution. When the thickness of the inner coating was 0.5 mm, the thermal insulation effect of the new oil pipeline improved by about 29%. This technology could be widely used in the production of deep oil and gas, high salinity oil and water reservoirs, thin oil reservoirs, etc., to alleviate scaling and waxing phenomena.

WAYS TO IMPROVE THE ENERGY EFFICIENCY OF PIPELINES AND STRUCTURES USING AEROGEL

Problem statement. The paper explores ways of energy saving in buildings, namely, the compliance of the regulatory framework with European standards, the possibilities of reducing heat losses during the transportation of energy carriers through pipelines on the example of heat supply systems and reducing heat losses during the operation of buildings and structures. The second part of the article presents the results of analytical studies of various heat-insulating materials that are most commonly used in Ukraine. Some of these materials cannot be used on structures and pipelines of complex configuration. The issue of energy efficiency, along with improving sound insulation properties, reducing fire hazard, and reducing loads on the load-bearing structures of buildings and structures, can be addressed by using aerogels as a thermal insulation material. The material is characterized by a low dependence of the thermal conductivity coefficient on changes in ambient temperature, which makes it the best option for use in harsh operating conditions. The purpose of the article is to consider ways to improve the energy efficiency of structures and pipelines using modern aerogel insulation material. Conclusions. Having conducted analytical studies of various thermal insulation materials, it was found that aerogels in roll form, in addition to a low heat transfer coefficient, are characterized by better performance properties, namely non-flammability of the material, environmental safety, low weight, which reduces the load on structures, ease of installation, the possibility of using for structures of complex configuration, and a high rate of sound insulation.

Pengembangan Media Flashcard Pada Pembelajaran IPA Materi Perpindahan Panas Kelas V Sekolah Dasar Kota Semarang

The purpose of this research is to produce a development product, namely learning Flashcard media with heat-insulating materials presented in the form of pictures and writing. Methods Data collection instruments used were observation, interviews, and documentation. the design of the development of Flashcard learning media on the hottest material can attract attention and generate interest in learning for fifth grade elementary school students in Banyumanik District, Semarang City. The eligibility of the media was also obtained from the educator's response to the Flashcard learning media on the heat locking material developed by the researcher. A score of 98% was stated in the very feasible category, which means that this Flashcard learning media received positive responses because the media can attract attention and increase interest in learning. student.

Research on New Solid Waste Heat Insulation Material for Deep Mining

The global demand for mineral resources has led to the gradual transformation of the mining industry from the traditional shallow, small-scale mining mode to the high-intensity mining of deep underground mines. Due to the high stress, high temperature, high permeability, and easy disturbance of deep mines, new challenges have been brought to the mining of materials. Some scholars have improved the thermal insulation performance of concrete by adding low thermal conductivity materials such as ceramsite, shell, and natural fiber to traditional shotcrete, but there are still high costs, insufficient support strength, and unsatisfactory thermal insulation effects. Given the background related to the fact that it is still not possible to fully recycle the large amount of solid waste generated by mining activities, this paper, with traditional shotcrete as its basis, uses coal fly ash to replace part of the cement and tailings to replace part of the sand and gravel aggregate. In addition, it adds basalt fiber to reduce thermal conductivity and restore strength. An orthogonal experiment of three factors and three levels was designed to explore a new type of solid waste-based thermal insulation support shotcrete material. Through the testing and analysis of the mechanical and thermal properties of the specimens, it was concluded that the optimal ratio of the materials was 45% fly ash, 50% tailings, and 25% basalt fiber (the percentage of the total mass of fly ash and cement). The compressive strength of the specimens after curing for 28 days could reach 16.26 MPa, and the thermal conductivity and apparent density were 0.228561 W/(m·k) and 1544.00 kg/m3, respectively. By using COMSOL Multiphysics multi-physics coupling software to analyze the coupling of the stress field and temperature field, it was concluded that the optimum thickness of the thermal insulation layer of this material was 150 mm. The field application in a mine in Shandong Province proved that it met the effects of thermal insulation (the ability to isolate heat conduction) and support. The successful trial of this material provides a new idea for the solving of the problem of heat damage and solid waste utilization in deep mines, which has a certain practical significance.

APPLICATION OF UHF INSTALLATIONS FOR THE MANUFACTUREOF MOLDED THERMAL INSULATION PRODUCTS BASED ON LIQUID GLASS

The article investigates the processes of swelling of liquid-glass compositions and the production of heat-insulating materials based on them under convective and microwave heating. In the work, it was established that the nature of the swelling curves of liquid-glass compositions under the conditions of microwave radiation and convective heating are significantly different. Thus, during convection heating, there is an induction period, but then the speed increases sharply and then the process gradually slows down. In the case of microwave radiation, there is no induction period, and the process proceeds at a high speed from the very beginning, and then slows down as the concentration of gas-forming substances decreases. In contrast to the swelling process under the influence of microwave radiation, during convective heating, the process proceeds uniformly with gradual release of water, as a result of which the material is mostly dried, and not swollen. A comparative analysis of the processes of swelling of liquid-glass compositions under convective and microwave heating showed a higher efficiency of swelling with the help of microwave radiation. The necessary duration of such heat treatment is 8-10 minutes. The materials obtained by convective heating at a temperature of 300 0C are the closest to such materials in terms of the swelling coefficient, the duration of such heating lasts more than 15 minutes. In addition, the calculated efficiency of the microwave installation is almost two times higher than the efficiency of the drying installation, for example, it is 0.79 for the microwave installation, and only 0.46 for the drying installation. Therefore, under the influence of microwave radiation, it is possible to produce effective heat-insulating materials based on liquid glass at lower temperatures and during a significantly shorter heat treatment time, compared to traditional convective heating. The work presents industrial microwave installations that can be used for the swelling process. These are chamber microwave installations of periodic action, which are used mainly for drying or heating large-sized products.

OPTIMIZING POROUS MATERIALS WITH PREDICTION THERMAL PHYSICAL CHARACTERISTICS

The article presents experimental data, based on which the influence of various factors on the strength and thermophysical characteristics of porous heat-insulating materials was studied.
 Porous bodies in thermal power engineering are used for thermal protection of power plants, various aggregates, in thermal insulation structures of buildings and technological networks. The properties of these materials and the field of use depend on their chemical composition and method of production.
 The task of this research is to obtain a raw material mixture for heat-insulating material of the closed-cell type with increased thermal resistance and porosity by optimizing its qualitative and quantitative composition. The goal is also to improve the method of obtaining porous heat-insulating material by changing the temperature and time regimes in order to improve the physical, mechanical and operational characteristics, which will allow the material to be used in a wider temperature range.
 Based on the dependences of strength and thermophysical properties on the density of the finished material obtained in the work, it was concluded that the best characteristics are the samples of the porous material with the lowest density, which are formed at the maximum humidity of the raw material. Kinetics of drying and heat treatment of the raw material mixture, thermal regimes are the main factors that determine the porosity, strength and thermal conductivity of the finished heat-insulating material.
 Performed laboratory studies of the material proposed in the paper allow choosing the required temperature regimes of heat treatment. Thus, the task of further research is to choose a method of organizing effective heat and mass exchange, modeling these processes, experimental testing of the obtained data, and creating a method for determining the main technological and structural parameters of the method of obtaining a new material.
 The performed experimental studies made it possible to determine the conditions for the implementation of new technologies for the production of porous materials with the possibility of predictive determination of their properties.

Obtaining Foamed Glass-Ceramics from Diamond Concentration Tailings

The possibility of obtaining building foamed glass-ceramic using the diamond concentration tailings of the Lomonosov deposit in Arkhangelsk Region, Russia, is demonstrated here. The effect of the tailings’ particle size distribution, feed temperature, the addition of a foaming agent, and the content of oxidizer on the feed charge foaming is established. The process conditions for obtaining foamed glass-ceramic materials are described. The specifications of the materials with the optimal composition (tailings 50 wt.%, glass waste 50 wt.%, SiC 0.5 wt.%, Fe2O3 1 wt.%) foamed at 1020–1050 °C were as follows: apparent density 0.23–0.51 g/cm3, compression strength 0.58–2.40 MPa, water absorption (by volume) 8.7–19.0%. Based on the combination of the measured properties when used in dry conditions, the obtained materials can be considered heat-insulating foam materials. The thermal conductivity was 0.060–0.066 W/m·K.