Lightweight Thermal Insulation Material Research Articles

Lightweight, hydrostatic pressure‐resistance, thermal insulating epoxy syntactic foam with a multiscale ternary structure for marine engineering application

AbstractThe study of lightweight epoxy syntactic foams is of great significance for the exploitation of marine resources. In this work, glass fibers reinforced epoxy hollow spheres (GFs‐EHS) were first prepared using a template method, and a lightweight three‐phase epoxy syntactic foam (LWTP‐ESF) with a multiscale ternary structure was prepared using a molding pressing method with epoxy resin as matrix, hollow glass microspheres (HGMs), and GF‐EHS as the lightweight fillers. The effect of HGMs content on the density, uniaxial compression properties, water absorption, and thermal conductivity of obtained LWTP‐ESF was evaluated. The results indicated that the density, uniaxial compression strength, and thermal conductivity of LWTP‐ESF were consistently decreased, while the water absorption was increased with the increase in HGMs content. The highest specific compression strength and lowest thermal conductivity of LWTP‐ESF could reach 52.77 ± 0.82 MPa·cm3/g and 0.113 ± 0.005 W/(m·K), respectively. Moreover, the effect of hydrostatic pressure on the water absorption and thermal conductivity of LWTP‐ESF were also systematically analyzed. This study provides a novel system and method to prepare lightweight epoxy syntactic foams, and the prepared composites have potential applications in the field of lightweight thermal insulation materials for marine.Highlights The composites with a multiscale ternary structure were designed. The composites possessed significantly lower density and thermal conductivity. The water absorption of composites under hydrostatic pressure was evaluated. The thermal conductivity of composites under hydrostatic pressure was evaluated. The water absorption mechanism and thermal insulation mechanism were proposed.

Ambient pressure dried polydicyclopentadiene based aerogels for low-cost lightweight thermal insulation materials

Ambient pressure dried polydicyclopentadiene based aerogels for low-cost lightweight thermal insulation materials

Fabrication, characterization, and application of light weight thermal insulation material from combined buffing dust and plaster of paris for construction industry

Buffing dust, generated from tannery industries, is a source of air pollution in Pakistan. Valorization of the waste into another useful material is important to deal with the environmental pollution, while reducing waste disposal costs in landfills. To demonstrate its technological strength, this work fabricates a thermal insulation material made of plaster of Paris and the buffing dust (from tanning waste) in the form of a composite with superior mechanical properties and low thermal conductivity. Buffing dust with concentrations ranging from 5 to 20% (w/w) were loaded in the composite. The samples synthesized were made slurry of plaster of Paris, buffing dust, and water at ambient temperature. The physico-mechanical properties of composite were analyzed. It was found that the composite had better thermal insulation properties than the panels of the plaster of Paris. Its thermal conductivity was reduced to 15% after adding buffing dust (20% w/w). All the materials had physico-chemical properties like tensile strength (0.02 MPa and 0.06 MPa), density (700-400 kg/m3), water absorption (5.2–8.6%) and thermal conductivity (0.17000–0.09218 W/m-K). Thermogravimetric analysis showed that the material was thermally stable at temperatures ranging from 145 to 177 °C, while FT-IR results revealed that the composite contained O–H, N–H, and CO functional groups. SEM analysis displayed that the composite's homogeneity was reduced with low voids due to buffing dust addition, while EDX analysis showed that the composite contained 23.62% of S, 26.76% of Ca, 49.2% of O and 0.42% of C. This implies that buffing dust could be recycled to manufacture heat insulation materials for construction sector to reduce air pollution, while minimizing energy consumption. By integrating the buffing dust from tanning waste and the plaster of Paris as a composite for construction sector, this work promotes the recycling of unused waste, while saving public funds. Instead of paying landfill fees and polluting soil, the waste may be recycled at lower cost, while reducing environmental damage.

Thermal properties of mullite based porous ceramics derived from high silica tailings obtained after extracting alumina from high alumina coal ash

In this study, to solve the problem of reducing the quantity and increasing the utilization of waste as resource for high silica tailings (HSTs) after extracting alumina from high alumina coal ash, lightweight thermal insulation materials for building were prepared by using the melt foaming method. The effects of the calcination temperature and holding time on the melting characteristics of ingredients with different melt indexes were investigated. The effects of the amount of foaming agent on the bulk density, total porosity, and thermal conductivity of porous ceramics were determined, and the thermal conductivity model structure was further elucidated by comparing the experimental data with the values predicted by a theoretical model. The results showed that porous ceramics with optimal performance were prepared by calcination at 1200 °C for 30–60 min with a melt index of 8 k, and the amount of added SiC foaming agent was 0.52 wt%. The bulk density, total porosity and thermal conductivity were determined for the prepared porous ceramics as 0.196 g cm−3, 93.8%, and 0.086 W m−1 K−1, respectively, where the added amount of HSTs reached 60 wt%. Comparison and verification of the thermal conductivity model confirmed that the prepared mullite based porous ceramics should be classified as materials with internal porosity, where the pores were dispersed in the mullite continuous phase to form isolated closed pores. The results obtained in this study are of economic significance for the reuse of HSTs at large dosages and with high added value.

Application of Lightweight Thermal Insulation Building Materials for Green Building Design

In order to focus on the application of green environmental protection lightweight thermal insulation materials, an in-depth study is carried out on the basis of joint architectural design. The application of green environmental protection materials in the construction industry was successfully analyzed through methods such as layout design method, optimization design method, and scientific optimization of material selection. In the process of urbanization development in our country, the number of urban population has increased sharply, and the demand for buildings has also increased. Therefore, it is necessary to rapidly promote green building design while the construction industry is developing rapidly and complete the upgrading and transformation of the building in terms of form design. We pay attention to the needs of buildings in terms of shading and lighting, and improve the conditions of building shading and lighting through green building technology. As a result, on the basis of maintaining the residual heat of the building, the diffuse radiation of the ultraviolet rays of the sun is realized, which effectively improves the utilization efficiency of natural energy and reduces the consumption of internal energy. Architectural design under the concept of green building design not only can it meet the current functional requirements of people for architecture but also imperceptibly promote the stable development of our country’s construction industry. After the research on the application of green environmental protection materials, the integration and application of green building design concepts in architectural design is of great significance not only to meet people's health and ecological needs of buildings but also to promote social stability and sustainable development.

The Aramid-Coating-on-Aramid Strategy toward Strong, Tough, and Foldable Polymer Aerogel Films.

Aerogel has been much highlighted as an emerging lightweight thermal insulation material, but problems such as fragility, low strength, liquid permeability, and lack of flexibility greatly limit further applications. In this work, a facile aramid-coating-on-aramid (ACoA) method is demonstrated to fabricate all-aramid aerogel composite films for thermal insulation. The method started from the bottom-up synthesis of polymerization-induced para-aramid nanofibers (PANF), which were easily transformed into aerogel films through the vacuum-assisted filtration followed by the freeze-drying techniques. Then, the heterocyclic aramid (HA) solution prepared through the low-temperature-solution polycondensation was used as the coating to be applied onto the PANF aerogel films, and composite films of HA/PANF aerogel were simply achieved with HA contributed to the dense and continuous surface layer. The bulk HA film is of superior mechanical and thermal properties to those of the PANF film. Moreover, reliable interfacial interlocking structures were developed beneath the outermost surface via the interpenetration of the infiltrated HA with PANF network. The comprehensive result was the 15 times enhanced tensile strength, 33 times enhanced fracture toughness, the high thermal decomposition temperature, and the additional flexibility for the foldable films of HA/PANF aerogel. The sealing of the surface macropores greatly suppressed the surface chalking and high water absorption. However, the survival of the tiny pores inside the composite maintained the low enough level of the thermal conductivity to provide effective protections against high temperature not only in air but also under wet or even liquid conditions, suggesting the broader applications for thermal insulation.

Carbothermal reduction synthesis of high porosity and low thermal conductivity ZrC-SiC ceramics via an one-step sintering technique

In this work, porous ZrC-SiC ceramics with high porosity and low thermal conductivity were successfully prepared using zircon (ZrSiO4) and carbon black as material precursors via a facile one-step sintering approach combining in-situ carbothermal reduction reaction (at 1600 °C for 2 h) and partial hot-pressing sintering technique (at 1900 °C for 1 h). Carbon black not only served as a reducing agent, but also performed as a pore-foaming agent for synthesizing porous ZrC-SiC ceramics. The prepared porous ZrC-SiC ceramics with homogeneous microstructure (with grain size in the 50–1000 nm range and pore size in the 0.2–4 µm range) possessed high porosity of 61.37–70.78%, relatively high compressive strength of 1.31–7.48 MPa, and low room temperature thermal conductivity of 1.48–4.90 W·m−1K−1. The fabricated porous ZrC-SiC ceramics with higher strength and lower thermal conductivity can be used as a promising light-weight thermal insulation material.

Fabrication of ultralight reticulated carbon foams for thermal insulation from raffinate pitch of low-temperature coal tar

A raffinate pitch of low-temperature coal tar and abundantly bamboo leaves are usually a waste material. This research proposes a new method for manufacturing an ultralight reticulated carbon foam for thermal insulation using a raffinate pitch and abundantly available bamboo leaves. The foam was successfully fabricated by a simple procedure consisting of co-pyrolysis of a raffinate pitch and abundantly available bamboo leaves. The effect of this procedure on the structure and performance of the carbon foams was investigated. The chemical composition of the raffinate pitch can be tailored by changing the concentration of bamboo leaves. The carbon foam containing 10 wt.% of bamboo leaves possessed the lowest density and thermal conductivity. The ultralight reticulated raffinate-pitched carbon foams also exhibited good oxidation resistance at 1000 ℃ in air. The foams had ultralow density, excellent thermal insulation, oxidation resistance, and compress strength compared with other coal tar pitch-based carbon foams. Therefore, these foams can potentially be used as lightweight thermal insulation materials.

Preparation of thermal insulation materials based on granite waste using a high-temperature micro-foaming method

ABSTRACT In this study, lightweight thermal insulation materials were successfully prepared in this study using a high-temperature micro-foaming method at 1200°C, where granite waste was the main raw material and SiC was the foaming agent. Further, the thermal insulation material’s macrostructure, microstructure, room temperature, and high-temperature performance have been investigated. This material has a small closed-cell porosity of up to 73.8%, high compressive strength of 18.2 MPa, low thermal conductivity of 0.22 W/(m•K) at room temperature and 0.17 W/(m•K) at 350°C, positive reheating linear change, and the refractoriness under load of 812°C, confirming that these materials can be used as good thermal insulation materials up to ~800°C.

Lightweight porous silica ceramics with ultra-low thermal conductivity and enhanced compressive strength

In recent years, the need for robust thermal protection for reusable spacecraft and vehicles has spurred strong demand for high-performance lightweight thermal insulation materials that exhibit high strength. Herein, we report silica porous ceramics prepared via the direct foaming technique with lightweight, ultra-low thermal conductivity and enhanced compressive strength. Silica particles (particle size: 500 nm and 2 μm) were used as the raw materials. The nano-sized silica particles were easily sintered, thereby improving the compressive strength of the ceramics, whereas the micro-sized silica particles maintained the pore structure integrity without deformation. The addition of nano-silica enhanced the compressive strength by 764% (from 0.039 to 0.337 MPa). In addition, the thermal conductivity of the ceramics was as low as 0.039 W m−1 K−1. Owing to these outstanding characteristics, these porous silica ceramics are expected to be employed as thermal insulation material in diverse fields, especially aerospace and space where weight is an important constraint.

Formation of Ultra-High Temperature Ceramic Hollow Microspheres as Promising Lightweight Thermal Insulation Materials via a Molten Salt-Assisted Template Method

Ultra-high temperature ceramics (UHTCs) have become a vital candidate material system for thermal protection systems in aerospace applications. However, high thermal conductivity and high density are the main obstacles to the application of UHTCs. It is a promising solution to prepare porous UHTCs using UHTC hollow microspheres (HMs) as a pore-forming agent. In this work, UHTC (ZrC, TiC, and HfC) HMs are successfully synthesized using carbon hollow microspheres (CHMs) as a template to react with metal powders in molten salt. The diameter of ZrC HMs is about 1 μm and the wall thickness is about 100 nm. The density of each microsphere and the volume fraction of ZrC are 3.36 g/cm3 and 48.42 vol %, respectively. The morphology, microstructure, and phase composition of the obtained ZrC HMs were characterized. The formation mechanism of the UHTC HMs was discussed. Porous ZrC ceramics were prepared using ZrC HMs as a pore-forming agent. The density and thermal conductivity of the porous ZrC ceramics are 3.12 g/cm3 and 1.82 W/(m·K), respectively, which are 53.64 and 91.12% lower than the density and thermal conductivity of dense ZrC ceramics, respectively. The results indicated that ZrC HMs are promising as pore-forming agents or a matrix for lightweight thermal insulation and high-temperature resistance applications in ultra-high temperature environments.

An inorganic thermal insulation material with good performance prepared from obsidian

Both obsidian and perlite belong to acid volcanic rock and have a similar structure and chemical composition, but the insulation material prepared from expanded obsidian cannot reach the performance level of that prepared from expanded perlite. To date, obsidian cannot be used in large quantities, although its resource is abundant. In order to comprehensively utilise this resource, in the present work the authors developed a new type of lightweight thermal insulation material by using obsidian as a main raw material which is energy-efficient and environmentally friendly. The effects of raw materials such as obsidian, sodium silicate, hydrogen peroxide and cetyltrimethylammonium bromide on physical properties including thermal conductivity, porosity, density and compressive strength were studied in detail. The optimised thermal insulation material exhibits low thermal conductivity (0.051–0.86 W m−1 K−1), low density (0.1–0.24 g/cm3) and adjustable compressive strength (0.09–1.52 MPa). Compared to other inorganic insulation materials, this new thermal insulation material is very light and has a better thermal insulation performance. Therefore, this work proposes a new energy-efficient way to prepare a promising noncombustible thermal insulation material, and also provides a way to use obsidian resources in large quantities.

Radiation Grafting Assisted Preparation of Layered Structure Polypropylene Foam with Superthermal Insulation and Hydrophobic Properties via a Supercritical CO2 Batch Foaming Process

A layered porous, high heat insulation, waterproof, and recyclable polypropylene (PP) foam was prepared by radiation grafting assisted supercritical CO₂ foaming. First, dodecafluoroheptyl methacrylate was grafted on PP powder via radiation-induced graft polymerization. Then the grafted product (PP-g) with a grafting rate of 12.8% was blended with PP powder, and subsequently the blends were foamed. The obtained PP/PP-g (10) foam exhibited a highly oriented layered cell structure and large expansion ratio, which largely increased the number of air layers of heat conduction and the length of the conduction path, so an ultralow heat transfer coefficient of 29.3 mW/m·k was achieved. In addition, the raspy surface of the PP/PP-g (10) foam possessed a highly hydrophobic property (water contact angle: 146.7 ± 0.5°). The method provides a new strategy for improving the thermal insulation and hydrophobic performances, which has outstanding potential application in lightweight thermal insulation materials.

Composite foamed alkali-activated concrete with slag and steel slag

Thermally expandable foaming microspheres (FMS) are used as a foaming agent in many different fields due to their excellent dimensional stability and elastic properties. In this study, lightweight thermal insulation materials were prepared by adding FMS to foamed concrete containing alkali-activated steel slag and blast-furnace slag. The dry bulk density, cube strength, thermal conductivity and drying shrinkage of samples with different compositions were investigated and their microstructure was analysed using scanning electron microscopy and X-ray diffraction. With the addition of FMS, foamed materials with a dry bulk density of 625 kg/m3 and 40 mm cube strength of 3·6 MPa could be obtained. The 28 d drying shrinkage was 0·8 mm/m and the thermal conductivity was 0·102 W/m.K (thermal inertia index of 4·66). The results showed that FMS can be used as an organic foaming agent to prepare lightweight thermal insulation materials with improved insulation performance and mechanical properties.

Low thermal conductivity and high porosity ZrC and HfC ceramics prepared by in-situ reduction reaction/partial sintering method for ultrahigh temperature applications

Porous ultra-high temperature ceramics (UHTCs) are potential candidates as high-temperature thermal insulation materials. However, high thermal conductivity is the main obstacle to the application of porous UHTCs. In order to address this problem, herein, a new method combining in-situ reaction and partial sintering has been developed for preparing porous ZrC and HfC with low conductivity. In this process, porous ZrC and HfC are directly obtained from ZrO2/C and HfO2/C green bodies without adding any pore-forming agents. The release of reaction gas can not only increase the porosity but also block the shrinkage. The as-prepared porous ZrC and HfC exhibit homogeneous porous microstructure with grain sizes in the range of 300–600 nm and 200–500 nm, high porosity of 68.74% and 77.82%, low room temperature thermal conductivity of 1.12 and 1.01 W·m−1 K−1, and compressive strength of 8.28 and 5.51 MPa, respectively. These features render porous ZrC and HfC promising as light-weight thermal insulation materials for ultrahigh temperature applications. Furthermore, the feasibility of this method has been demonstrated and porous NbC, TaC as well as TiC have been prepared by this method.

Mechanical, thermal and fire performance of an inorganic-organic insulation material composed of hollow glass microspheres and phenolic resin

HypothesisOrganic foamy materials possess good thermal insulation properties and inorganic materials are non-combustible. Hence, it is possible to develop a kind of organic-inorganic lightweight thermal insulation materials with excellent fire safety. ExperimentsHollow glass microsphere (HGM), as one kind of lightweight noncombustible inorganic material, was chosen as the filling material. Phenolic resin (PR), as the flame retardant polymeric material, was used as binding material. A series of HGM/PR composites with various PR/HGM mass ratio were prepared. Properties, such as apparent density, microstructure, mechanical strength, thermal conductivity, burning behavior and flame retardancy of the specimens were determined, respectively. FindingsThe results show that the surface of HGM particles is coated by a layer of cured PR and the HGM powder is glued together firmly from the scanning electron microscope (SEM) images. With the increase of PR/HGM mass ratio, both of apparent density and mechanical strength of HGM/PR composites increase, but thermal conductivity and limiting oxygen index (LOI) values decrease, all of the specimens still possess high LOI value (>50%). What’s more, no flaming combustion (merely partial carbonization) and hardly any smoke can be observed during the burning process, which indicates the HGM/PR composites possess excellent flame retardant property and fire safety.

Insulation Performance of Heat-Resistant Material for High-Speed Aircraft Under Thermal Environments

Lightweight insulation materials are widely used to thermally protect high-speed aircraft, such as missiles. Thermal conductivity is an important parameter used to evaluate the efficiency of a material’s thermal insulation performance. Since thermal conductivities provided from material handbooks or manufacturers are discrete data for different temperature ranges, there is a deviation between those and actual parameters in terms of continuous nonlinear variations. Therefore, this study measures the thermal conductivities of lightweight thermal insulation materials at high temperatures, and the relationship between the thermal conductivity and temperature is obtained. A finite element model of the thermal insulation materials is also established and applied to numerically calculate the thermal insulation properties for high-temperature ceramic fiber insulation materials using the experimentally obtained nonlinear relationship between thermal conductivity and temperature. Additionally, a transient aerodynamic heating experiment simulation system is used to thermally test the same materials; the calculated and experimental results for the same materials are compared, which exhibit good consistency that demonstrates that accurate results can be obtained from the numerical computation using the relationship established from the experimentally measured conductivity and temperature.

발포공정을 이용한 경량의 연질 세라믹 보온단열재의 제조

본 연구는 유기계 보온단열재의 장점인 경량성과 연질특성을 갖는 무기계 보온단열재의 제조를 위한 새로운 개념의 무기질 저온 발포 공정에 관한 것이다. 새로운 무기질 발포 공정은 섬유상인 해포석 및 규산알루미늄으로 하여금 발포체의 골격을 형성토록 하고, 저온에서 기체 발생이 가능한 발포제를 사용하여 무기질 섬유상 골격체가 팽창되어 공동을 형성하게 하며, 이 형성된 공동 속에 낮은 열전도도를 갖는 무기질 다포체인 팽창진주암을 채우는 것이다. 총괄적으로 무기질 재료를 고온 용융함이 없이 저온에서 무기질 발포체의 제조가 가능하게 된다. 이를 위해서 섬유상인 해포석의 해섬처리과정, 발포를 위한 섬유상 슬러리의 열처리공정 등 다양한 준비공정이 필요하며, 열처리 전 슬러리의 최적 조성물 조건이 요구된다. 제조된 발포체는 경량, 연질의 보온단열재로서의 겉보기 밀도, 내력 강도, 굽힘강도, 고내열성 등의 물성을 보여주었다. A new concept of an inorganic foaming process at low temperature was demonstrated for the production of inorganic thermal insulating materials with the properties of flexible light-weight, the advantages of organic-based thermal insulation material. The foaming process was proceeded by establishing a skeleton of the foam body by using inorganic fibrous sepiolite and aluminum silicate. A cavity was formed by the expansion of fibrous skeleton body, by the gas which was generated from foaming agent at low temperature. Then the multi-vesicular expanded perlite with low thermal conductivity was filled into the cavity in a skeleton of the foam body. Finally through these overall process, a new inorganic foamed body could be obtained at low temperature without the hot melting of inorganic materials. In order to achieve this object, various preparations such as fibrous sepiolite fibrillation process, heat treatment process of the fibrous slurry were needed, and the optimal compositional condition of slurry was required. The foam body produced showed the properties of flexible light-weight thermal insulation materials such as bulk density, yield strength, flexural strength, and high heat resistance.

The Effect of Expanded Perlite on the Performance of the Lightweight Wall Materials

This paper studied the produce process of the lightweight wall material (LWW). The main components of LWW were expanded perlite (EP) and Portland cement (PC). An experimental investigation was carried out to study the effect of EP on the performance of LWW, such as the bulk density, the strength property and thermal conductivity. The experimental results indicated that the products can be divided into lightweight structural materials and lightweight thermal insulation materials.

Effect of Material Constitution on the Properties of Thermal Insulation Materials

Cement-based foam insulation board is a lightweight thermal insulation and have a characteristic of energy saving. The effects of material constitution on the properties of mechanical properties, dry densityand thermal conductivity for thermal insulation materials. The subject of fast hardening sulphoaluminate cement as cementitious materials, polystyrene particles as a lightweight thermal insulation material, adding a certain amount of water reducer, cellulose ethers, air entraining agent to make thermal insulation materials. The experimental results shows that the appropriate material constitution is following: the cement-bead ratio is 12, the ratio is 0.65, the water-cement ratio is 0.4, the content of water reducer is 0.5%, the content of cellulose ether is 0.4%, the content of the air entraining agent is 0.4% .This mix ratio test of mechanical properties are: flexural strength is 0.72MPa, compressive strength is 1.24MPa, dry density is 375kg/m3, water content is 2.3%, water absorption is 10.8%, softening coefficient is 0.95 and coefficient of thermal conductivity is 0.053 W/ (m K).