Lightweight Insulation Materials Research Articles

Ultralight M5 aerogels with superior thermal stability and inherent flame retardancy.

Ultra-lightweight materials often face the formidable challenge of balancing their low density, high porosity, high mechanical stiffness, high thermal and environmental stability, and low thermal conductivity. This study introduces an innovative method for synthesizing high-performance polymer aerogels to address the challenge. Specifically, we detail the production of poly (2,5-dihydroxy-1,4-phenylene pyridine diimidazole) (PIPD or M5) aerogels. This process involves chemically stripping M5 "super" fibers into nanofibers, undergoing a Sol-Gel transition, followed by freeze-drying and subsequent thermal annealing. The M5 aerogels excel beyond existing polymer aerogels, boasting an ultralight density of 6.03 mg cm-3, superior thermal insulation with thermal conductivity at 32 mW m-1 K-1, inherent flame retardancy (LOI = 50.3%), 80% compression resilience, a high specific surface area of 462.1 m2 g-1, and outstanding thermal stability up to 463 °C. These multi-faceted properties position the M5 aerogel as a front-runner in lightweight insulation materials, demonstrating the strategic use of high-performance polymer assembly units in aerogel design.

Synthesis and characterization of aluminum hydroxide-reinforced silica-zirconia ceramic membrane for thermal protection applications

In the domain of personal thermal protection, there is a growing demand for lightweight and efficient ceramic thermal insulation materials. However, conventional ceramic membranes face challenges such as brittleness, structural collapse, and pulverization, hindering their practical application. To address this issue, aluminum hydroxide-enhanced silica-zirconia ceramic membranes (SZ@ANFMs) have been successfully fabricated using electrospinning followed by subsequent calcination processes, and their properties have been comprehensively evaluated. The results demonstrate that SZ@ANFMs exhibit outstanding high-temperature resistance under an alcohol lamp, along with an extremely low thermal conductivity (only 0.041 W/m·K), excellent tensile strength (2.3 MPa), and flexible characteristics. This makes them highly promising in the domain of personal thermal protection. The study builds upon existing research in lightweight and efficient thermal insulation materials, offering improvements and robust support for the further development of personal thermal protection technology.

Research on the performance of foamed concrete based on superhydrophobic bulk modification

Foamed concrete is a kind of lightweight insulation material formed by the uniform mixture of foam and cement slurry. The superhydrophobic bulk modification of foamed concrete can reduce its high water absorption and prolong its service life. In this paper, the compatibility of three hydrophobic agents named polydimethylsiloxane (PDMS), isoctyltriethoxysilane (ICTS) and SBT®-TIA with foams was studied, and the reasons of incompatibility were revealed. Then, the superhydrophobic bulk foamed concrete system was constructed by physical foaming method, adding polydimethylsiloxane (PDMS), calcium stearate (CS), nano-silica (NS) and covering the surface of the specimen with 200-mesh wire mesh. The results show that the maximum contact angles of the meshed surface and the internal polished surface of superhydrophobic foamed concrete were 162.7° and 153.5°, respectively. At the same time, the water absorption rate of the modified specimen was significantly reduced, and the reduction rate was up to 90 %. In addition, the deterioration degree of thermal insulation performance after soaking and the dry shrinkage rate were significantly reduced compared with ordinary foamed concrete. Scanning electron microscopy (SEM) revealed that increasing the multi-scale roughness could improve the hydrophobic properties of foamed concrete. Fourier infrared spectroscopy (FT-IR) also confirmed that low surface energy groups such as -CH2 and -CH3 in PDMS bonded to the cement hydration products, indicating the successful preparation of superhydrophobic bulk foamed concrete.

Facile Synthesis and Properties of Highly Porous Quartz Fiber-Reinforced Phenolic Resin Composites with High Strength.

Lightweight and high-strength insulation materials have important application prospects in the aerospace, metallurgical, and nuclear industries. In this study, a highly porous silica fiber reinforced phenolic resin matrix composite was prepared by vacuum impregnation and atmospheric drying using quartz fiber needled felt as reinforcement and anhydrous ethanol as a pore-making agent. The effects of curing agent content on the structure, composition, density, and thermal conductivity of the composite were studied. The mechanical properties of the composite in the xy direction and z direction were analyzed. The results showed that this process can also produce porous phenolic resin (PR) with a density as low as 0.291 g/cm3, where spherical phenolic resin particles are interconnected to form a porous network structure with a particle size of about 5.43 μm. The fiber-reinforced porous PR had low density (0.372~0.397 g/cm3) and low thermal conductivity (0.085~0.095 W/m·K). The spherical phenolic resin particles inside the composite were well combined with the fiber at the interface and uniformly distributed in the fiber lap network. The composite possessed enhanced mechanical properties with compressive strength of 3.5-5.1 MPa in the xy direction and appeared as gradual compaction rather than destruction as the strain reached 30% in the z direction. This research provides a lightweight and high-strength insulation material with a simple preparation process and excellent performance.

A lightweight and high compressive resistance thermal insulation material with dual-network structure

A lightweight and high compressive resistance thermal insulation material with dual-network structure

Sound insulation enhancement of PVB film by additive engineering

In recent years, noise pollution has become a prominent topic in the energy field. The lightweight and high sound insulation materials have attracted more and more attentions. This study focuses on improving the sound insulation properties of PVB films by adding a little water during the processing. When the water content was 4 %, the average sound transmission loss improved by 5.7 dB at 500–1100 Hz, with a maximum improvement of 17.6 dB, due to porous structure formed by the water additives. Meanwhile, the tensile stress was 28.1 MPa and the elongation at break achieved 140.4 %, which were 1.06 and 1.24 times higher than that of PVB without water, respectively. The porous structure and sound insulation mechanism for PVB films were characterized by SEM, BET and acoustic impedance tubes, etc. .1

Multicomponent Si–Zr-based lightweight nanofiber films with a hollow structure exhibiting excellent thermal insulation properties

Hollow-structured ceramic fibers with multiple components are ideal as lightweight insulation materials. In this study, tetraethyl orthosilicate, boric acid, and zirconia octahydrate were used as raw materials for fabricating SiZrBOC hollow ceramic fibers through coaxial electrospinning. These ceramic fibers exhibit a low thermal conductivity and an excellent temperature resistance. The electrospun SiZrBOC hollow ceramic fibers display a clean and compact morphology with internal folds. Fourier-transform infrared spectroscopy and thermogravimetric analysis (TGA) were used to assess the transformation process and thermal behavior of the hollow ceramic fibers. The results suggest that the incorporation of B promotes the formation of Si–O–B bonds within the system, leading to a maximum yield of 75.49 wt% for the production of the SiZrBOC hollow ceramic fibers. The phase composition and microstructure of the SiZrBOC hollow ceramic fibers were analyzed via X-ray diffraction (XRD) measurements. The pyrolysis at 1000 °C resulted in the appearance of diffraction peaks corresponding to SiO2 and SiC in the XRD patterns of the SiZrBOC hollow ceramic fibers. Laser thermal conductivity measurements reveal that the SiZrBOC hollow ceramic fibers exhibit a thermal conductivity of only 0.06 W‧m−1K−1 at 25 °C and 0.124 W‧m−1K−1 at 500 °C, indicating a significantly superior thermal insulation performance compared with conventional solid SiZrBOC ceramic fibers.

Tuning the Degree of Protonation to Prepare Ultra-light and High Thermal Insulation Mullite Nanofiber Aerogels

Ceramic fiber aerogels play an important role in thermal insulation due to their high specific surface area and porosity. They have great potential in aircraft, the military industry, and metal smelting. Although traditional ceramic fiber has the advantages of high-temperature resistance, its brittleness, tensile resistance, and high production cost, greatly limit the application of ceramic aerogels. Using the sol-gel method and electrostatic spinning technique, we controlled the fibers’ random winding and mechanical properties by controlling the protonation of the spinning fluid. We prepared ultralightweight, flexible, and highly insulated mullite nanofiber aerogels with a volume density as low as 7 mg / cm3, thermal conductivity as low as 27 mW m−1 K−1, excellent thermal stability at 1,300 °C, high thermal insulation and retention of up to 50% of the ceramic fiber after initial compression. This material’s fabrication process and excellent insulation properties propose new opinions on the lightweight and durable insulation materials needed for aerospace and military insulation.

Uniaxial dynamic behavior of foam glass aggregate under oedometric (fully side restrained) condition at different compaction ratios

Foam glass aggregate (FGA) is considered as a lightweight and thermal insulation material. It has a wide granular size distribution nature that can influence the material's dynamic response when subjected to moving loads. Therefore, it is crucial to investigate the impact of different compaction ratios on the material's dynamic behavior. This study focused on examining the effects of varying compaction ratios (10%, 20%, 30%, and 40%) on dynamic parameters such as resilient stiffness (Mr) and accumulated plastic strains (ɛacc) of FGA. Uniaxial deviatoric stresses were applied to the material samples in a series to assess their influence on the material's behavior over multiple cycles. The results revealed the significant influence of increasing the compaction ratio to 40% on the material's behavior. At this compaction ratio, the ɛacc decreased to approximately 71%, 69%, and 86% for deviatoric stresses of 25 kPa, 100 kPa, and 200 kPa, respectively, after subjecting the material to 40,000 cycles. The increase in recoverable strains resulting from the material's fragile property under higher compaction energy led to a decrease in the Mr values of FGA samples as the compaction ratios increased. The lower boundary of Mr values for FGA ranged from 102 MPa to 189 MPa, while the upper boundary ranged from 150 MPa to 219 MPa under the selected deviatoric stresses. Although the interpretation of the shakedown criterion limitations yielded varying ranges for the colocation of FGA samples, it was found that FGA samples compacted at 40% exhibited robust characteristics suitable for constructing road embankments. This can be beneficial for infrastructure applications due to their excellent lightweight and thermal insulation properties.

Mechanical and thermal properties of lightweight concrete produced with polyester-coated pumice aggregate

With the technological advances in the field of building materials, there has been an increasing focus on the research of lightweight concrete made with coated aggregates for improving the durability of concrete. In this study, pumice aggregates were coated with cast-based polyester to obtain polymer-coated pumice aggregates (PCPA). Lightweight concretes were produced with different cement dosages (200, 250 and 300) and PCPAs at different ratios (0%, 50% and 100%). Physical properties, mechanical strength, thermal properties and internal structure analysis (SEM-EDS) of the produced concrete samples were performed. According to the RILEM functional classification of lightweight concrete, the test results showed that REF D300 and REF D250 dosage series are in the semi-load-bearing lightweight concrete class, and the other all series are in the insulation concrete class, and the produced concretes can be classified as lightweight insulation materials. It can also be used in non-load-bearing walls or as an alternative lightweight insulation material.

Anisotropic and high-strength SiO2/cellulose nanofiber composite aerogel with thermal superinsulation and superhydrophobicity

SiO2 aerogel is a promising lightweight and high-efficiency thermal insulation material for applications in construction, industrial, aerospace vehicles, etc., but weak mechanical properties limit its further development and application. In order to overcome this challenge, we combined the design concepts of elastic group's introduction and structural strengthening of cellulose nanofibers with a directed freezing process, and successfully realized an anisotropic and high-strength SiO2/cellulose nanofiber composite aerogel. Under the low density of 0.247 g/cm3, the maximum compression strength of the aerogel in the radial direction is as high as 18.08 MPa, corresponding to a high fracture strain of 75.67%, and it also exhibits an excellent fatigue resistance, with only a slight plastic deformation of 6.5% after 100 load-unload cycles at a high compression strain of 50%. In addition, the aerogel exhibits an ultra-low thermal conductivity (0.01714W/(m·K)) in the radial direction, and also has a superhydrophobicity (water contact angle 150.8°) and a long-term hydrophobic stability (saturated mass moisture absorption rate 0.44%). The combination of these properties makes it an ideal material for thermal superinsulation in environments where both integrated mechanical properties and hydrophobic properties are critical.

Study of effective thermal conductivity of a novel SiO2 aerogel composite for high-temperature thermal insulation

A SiO2 aerogel composite doped with novel spherical hollow carbon@SiC infrared opacifiers was proposed. Finite-Difference Time-Domain (FDTD) combined with the Rosseland approximation techniques were used to numerically calculate the radiative properties and thermal conductivity under a large temperature range of 300–1400 K. The obtained results demonstrate that the addition of a large hollow between carbon and SiC into the core-shell opacifier can suppress radiation heat transfer at high temperature without increasing the solid heat conduction and density of the composite. Furthermore, spectral transport approximation in relation to the isotropic property of the novel opacifier was established. The findings indicate that the composite can be used as a lightweight and efficient thermal insulation material at high temperature.

A lightweight rubber foaming insulation reinforced by carbon nanotubes and carbon fibers for solid rocket motors

The development of lightweight insulation materials has become one of the effective ways to improve the performance of solid rocket motors (SRMs). In this paper, porous structure was introduced into ethylene propylene diene monomer (EPDM) insulation materials through rubber foaming technology to prepare lightweight insulation materials. The influence of foaming agent content and pre-curing temperature on morphology and properties of EPDM rubber foams were investigated. With the increase in pre-curing temperature, the cell size decreases significantly and the cell becomes more uniform, resulting in an increase in mechanical properties. As the foaming agent content increases, the cell density increases gradually without significant change in cell diameter. Meanwhile, the mechanical properties of insulation materials gradually decrease. EPDM rubber foams have optimum ablation resistance when the pre-curing temperature is 120 °C and the content of foaming agent is 6phr. Its charring ablation rate is 0.186 mm/s, only increasing by 16% compared with that of basic formula. On this basis, carbon nanotubes (CNTs) and carbon fibers (CF) were added to reinforce EPDM rubber foams. The tensile strength of the reinforced formula increases by 36.4% compared to the foaming formula, which is 19.2% lower than that of the basic formula. The charring rate of the reinforced formula decreases by 35.5% compared to the foaming formula, which is only 5.3% higher than that of the basic formula.

Fabrication of Light-weight Ceramic Insulation Materials by Using Oxide Ceramic Fibers for Reusable Thermal Protection Systems

Fabrication of Light-weight Ceramic Insulation Materials by Using Oxide Ceramic Fibers for Reusable Thermal Protection Systems

Flexural–Shear Performance of Lightweight Concrete Panels with High Insulation Capacity

With the increased interest in the inherent fire resistance of organic insulators, various precast concrete insulation panels have been developed. However, precast concrete insulation panels still have structural and fire resistance problems resulting from a low composite action and unclosed cross-sectional details. To improve composite action and fire resistance, this study proposes the closed cross-sectional details of insulator panels with lightweight aggregate concrete, insulation material, and wire mesh. The objective of this study is to examine the flexural–shear performance of precast lightweight concrete panels with closed cross-sectional details developed for exterior cladding with high insulation capacity. Six full-sized insulation panels were tested under two-point top loadings. The main investigated test parameters to vary the moment–shear ratio of the insulation panels were the amount of the shear reinforcement and shear span–effective depth ratio. Test results indicate that the insulation panels with moment–shear ratios of 2.60 or higher were governed by shear, indicating that the longitudinal bars remained in an elastic state until the peak load of the insulation panels was reached. Thus, an increase in the moment–shear ratio of the insulation panels led to more brittle failure characteristics. Meanwhile, the insulation panels governed by flexure exhibited plastic flow performance in the applied load–deflection curve and well-distributed cracks. In particular, the maximal flexural moments of insulation panels with moment–shear ratios of 0.75 or less were higher than those calculated from the equations specified in ACI 318-19, indicating that the composite action was fully exerted. Overall, the developed insulation panels with cross-sectional details must be designed to a have moment–shear ratio of 0.75 or less to fulfil the ductile response under extreme lateral loads and exert full composite action.

Biomimetic Swallow Nest Structure: A Lightweight and High-Strength Thermal Insulation Material.

A common method for reducing carbon emissions and the load-bearing pressure of buildings, and while also achieving improved energy conservation is to prepare porous magnesium-based lightweight composites to reduce waste and environmental hazards. However, due to internal stress, the pores of traditional lightweight composites crack easily and collapse, resulting in composites that are brittle with poor water resistance. These materials cannot achieve both low density and high strength, which limits their application in advanced functional materials. Thus, learned from nature, inspired by swallow's nest, a solution has been proposed, which is a simple and fast chemical arrangement and assembly method. Using bamboo scraps as the supporting framework and methylcellulose (MC) molecular chains as the templates, 5-phase crystals are grown and arranged on the MC. These crystals are arranged on the bamboo scraps by chemical means with MC acting as a bridge. At the same time, using the high viscosity and flexibility of the vinyl acetate/ethylene (VAE) copolymer emulsion and the formation of magnesium acetate chelate from VAE and hydration products, crystals and bamboo scraps can be assembled. Through these organic-inorganic copolymers, an intercalated and integrated biomimetic swallow nest structure is formed. The biomimetic swallow nest structure composites (BSNSC) imitated the formation process of a natural swallow nest. It is a lightweight material with a thick wall, low connectivity rate, and regular shape. Its density is 0.42 g/cm3, which is still in the density class of ultralight inorganic foam materials, and its compressive strength reaches 6.5 MPa, three times that of ordinary composites. The structure has a strength-to-weight ratio 3.5 times that of ordinary composites and a thermal conductivity much lower than of other thermal insulation materials. In the future, this type of lightweight composites with high strength, high heat insulation, and low density not only functions as a good energy-saving material for buildings but also a good thermal insulation material in the aerospace field.

Chemical, mineralogical, and microstructural interactions between lime-pozzolan binders and miscanthus particles in lightweight concretes

The incorporation of bio-aggregates such as miscanthus in mineral binder matrices can produce lightweight insulation materials. Bio-aggregate lightweight concretes show peculiar microstructure compared to standard mineral aggregate concretes. This paper evaluates the chemical and mineralogical interactions between miscanthus particles and blends of mineral binders that include hydrated lime (CL90s), natural hydraulic lime (NHL3.5), formulated lime (FLA3.5) and mineral additions such as ground granulated blast furnace slag (GGBS), fly ash (FA) and Portland cement (Ce). The properties and the influence of ternary binder blends made of 75%CL90s, 15%NHL3.5 and 10% mineral additions (GGBS/FA/Ce) on the morphology of the interfacial zone were investigated. It was observed that carbonation of samples proceeds from the outer shell to the inner core of samples leaving a physically identifiable hardened shell (external 1–2 cm) and a softer inner core. In all samples, the X-ray diffraction results show that there is a reduction in peak intensities and broadening of Ca(OH)2 peaks whereas peaks of CaCO3 sharpen and increase in intensity. The mineralogical changes in the binding matrix depend on the type of mineral addition. Thermogravimetric analysis shows that the addition of 10% Portland cement results in the highest levels of carbonation (1.1–1.4%) and hydration (8.6–17.1%). However, also fly ash incorporation was found to be beneficial in terms of reaction processes, and its use can have positive environmental impacts due to its low embodied carbon. FTIR results show that the chemical composition of miscanthus surface changes in contact with all binders, with effects on the structures of both hemicellulose and lignin.

Assessment of moisture and mould of hempcrete and straw panels

At present buildings contribute a third of total greenhouse gas emissions. There is a need for sustainable solutions and natural materials, which offer low-embodied energy and their low impact has a promising potential as construction alternatives. Hempcrete is a lightweight insulation material, which provides natural, airtight, and vapor-permeable insulation. Straw panels are also natural construction materials and they consist of extruded wheat straw and are surrounded with recycled paper on all sides. There are some risks, which can be associated with the use of such materials - infestation, biological degradation, presence of moisture, and structural degradation. The aim of the study is to determine the critical moisture level and mould resistance of hempcrete and straw panels. The results of this study are valuable to both scientists and structural engineers.

Facile synthesis, mechanical toughening, low thermal conductivity and fire-retardant of lightweight quartz fiber reinforced polymer nanocomposites

Lightweight and nanoporous composite materials with excellent thermal insulation and strong mechanical property are urgently required to address prominent issues that pertain to application. The main challenge of synthesizing such materials is to reduce the thermal conductivity and improve its rigid-flexible combined property as well as its heat resistance. Here, we propose to prepare a completely lightweight 3D bulk composites by vacuum impregnation and gel polymerization processing with a needled quartz fiber felt (NQF) as the reinforcement and phenolic resin aerogel (PR) as the matrix. The nanoporous PR is facilely synthesized by polymerization-induced phase separation with phenolic resin, and the resultant nanoporous PR is uniformly filled and distributed in NQF without macroscopic cracking and agglomeration. The as-prepared NQF/PR nanocomposites possessed enhanced mechanical property with compressive strength (1.76–2.84 MPa) and Young's modulus (26.71–39.60 MPa) in the xy direction. Importantly, the NQF/PR nanocomposite was not damaged as the strain reached 50% in z direction. Compared to most organic-based aerogel and aerogel-like materials, the present NQF/PR nanocomposite aerogels exhibited excellent flame resistances with 1000 °C fire duration time exceeding 30 min and excellent thermal insulation properties with low thermal conductivities that varied from 0.017 W/m⋅K to 0.031 W/m⋅K. This experimental results show that the synthesized NQF/PR nanocomposites by this method are very suitable to heat high-performance lightweight insulation materials for industrial compatibly and production.

Lightweight, high-strength, flexible YAG fibrous membrane for efficient heat insulation

Lightweight and flexible thermal insulation materials have gradually become a research focus. In this work, the flexible YAG fibrous membrane which can be folded in half after heat treatment at 1200 °C for 2 h was prepared. The crystallization process, mechanical properties, and thermal insulation properties of the YAG fibrous membrane were studied. The as-prepared YAG fibrous membrane has no mesophase formation during the crystallization process, and its tensile strength was 2.43 MPa. The self-supporting effect of single fibers made YAG fibrous membrane had ultra-high porosity. Its density was 27.34 mg/cm3, which made it have thermal insulation performance comparable to aerogel. When the hot surface is 1200 °C, a 10 mm thick YAG fibrous membrane can stabilize the temperature of the cold surface at 320 °C. The YAG fibrous membrane is expected to be used as a new generation of lightweight, high strength, flexible, and high-efficiency thermal insulation materials for extremely high temperature conditions.