Fibrous Insulation Research Articles

Evaluation of Reusable Thermal Protection System Materials Using a High-Velocity Oxygen Fuel Torch.

We studied a candidate TPS (thermal protection system) material for reusable re-entry space vehicle applications. The material was based on a high-temperature-resistant material called Cerakwool. A total of six specimens were fabricated with substrate densities of 0.45 g/cm3, 0.40 g/cm3, and 0.35 g/cm3, with two specimens for each density. All specimens were coated with high-emissivity TUFI (toughened unpiece fibrous insulation), with coating thicknesses ranging from 445 to 1606 µm. The specimens were tested using an HVOF (high-velocity oxygen fuel) material ablation test facility. For each density specimen pair, one specimen was tested at 1 MW/m2 and the remaining one was tested at 0.65 MW/m2. The average stagnation point temperature for specimens tested at 1 MW/m2 was ~893 °C, approximately 200 °C higher than those tested at 0.65 MW/m2. This suggests a ~200 °C increase in stagnation point temperature for a 0.35 MW/m2 rise in incident heat flux. During the tests, internal temperatures were measured at three locations. For all tested specimens, regardless of heat flux test conditions and density, the temperature at ~40 mm from each specimen's stagnation point remained around or below 50 °C, well within the 180 °C design limit set for the TPS back face temperature. Post-test visual inspections revealed no signs of ablation or internal damage, confirming the material's reusability.

A novel ultra-light bio-based fiberboard from mexican feather grass for thermal and acoustic insulation in green building construction applications

The use of natural fibers as raw materials for insulation fiberboard production is emerging as a strategy to replace wood fibers. This study developed an ultralightweight natural fiber insulation core fiberboard (CFB) with high mechanical strength, hygroscopic resistance, and excellent acoustic and thermal insulation properties. This study examined the production of CFB, which utilizes Mexican feather grass fibers with an epoxy resin binder across a range of densities of 0.18–0.36 g∙cm−3. Furthermore, the impact of incorporating a reinforcing skin layer of woven glass fibers on the core fiberboard's physical, mechanical, acoustic, and thermal properties was evaluated. All the fiberboard samples exhibited excellent thermal conductivity values (0.048–0.057 W/mK), which increased with increasing panel density (0.18–0.36 g∙cm−3). In addition, all of them displayed superior mechanical properties following the ASTM C208 standard. In terms of climatic resistance of the fiberboards, the results displayed excellent water resistance, exhibiting minimal humidity content (<5 %), thickness swelling (<6.5 %), and a hydrophobic surface, as indicated by the high-water contact angle (>121.96 at 30 s). Sound reduction exhibited a frequency-dependent tendency, with denser and sandwich fiberboards showing greater sound reduction of up to 27.9–36.56 dB at 3150 Hz for CFB-0.36 and SFB-0.52, respectively. Following ASTM C208, both core fiberboards and those coated with woven glass fiber skins (sandwich fiberboards, SFB) met the thermomechanical property requirements for regular and structural wall sheathing applications, respectively. These findings highlight the potential of Mexican feather grass as a bio-based alternative to wood, enabling the production of eco-friendly ultralightweight fiberboards with excellent thermomechanical properties suitable for building construction, such as regular and structural wall sheathing applications and ceiling decorations.

Wood-fiber insulation boards (WFIB) produced with hardwood and softwoods species and polylactic acid (PLA) fibers as a binder

ABSTRACT Wood fiber insulation boards (WFIB) produced with natural binders have been gaining recognition as an eco-friendly material, however there is limited information on the effect of different wood fiber and sustainable binders on WFIB production. This study investigates the impact of density, wood fiber origin, and pertinency of polylactic acid (PLA) as a binder. Flexible WFIB with densities of 80, 100 and 120 kg/m3 were produced by hot-press method with fibers of pine and spruce as softwoods, and beech and birch as hardwoods. Bicomponent fibers, composed by two concentrical layers of polylactic acid (PLA) were utilized as a renewable-origin binder at a proportion of 10%. Technological properties such as short-term water absorption, compression test and thermal tests properties were assessed. The density of the WFIB significantly influences the water absorption, compression strength, and thermal conductivity, with all these values increasing as the density rises. Insulation boards made from hardwood fibers showed greater water absorption and compression values compared than their softwood counterparts. Softwood-WFIB single-samples with a density of 80 kg/m3 reported lower thermal conductivities than hardwoods ones. The present study shows the promising feasibility of producing flexible wood fiber insulation boards from natural fibers and polylactic acid as a renewable binder.

Optimization of microwave-produced coal-derived char insulation foam using response surface methodology

A new char-based insulation foam (CIF) is developed using coal-derived pyrolysis char (PC) and lignin, a paper and pulp industry byproduct. In this study, CIF is prepared by adopting the microwave method and Response Surface Methodology (RSM) is utilized to optimize predictions about the properties such as thermal conductivity, foam texture, compressive strength, and pore distribution of CIF. The three independent variables including percent char content, lignin/char ratio, and foaming agent/polyol ratio are considered in the RSM methodology. The face-centered central composite design is selected to obtain 17 test runs. Optimization of the predicted responses is performed to find the recipe considering a composite desirability function. Confirmatory test results show agreement between the predicted and observed values, with the percent error ranging from 0.00 % to 11.35 %, thereby confirming the accuracy of the prediction equations. The optimized CIF exhibits a thermal conductivity of 0.0633 W/m.K and a compressive strength of 695 kPa making it comparable to or better than traditional building insulation products such as fiber insulation, polymer composite, particle board, and ceramic glass foam. Therefore, this new CIF has the potential to be used as an energy-saving insulation material for building envelopes.

Study on the effect of heat treatment on the structure, mechanical and electrical properties of alumina fiber insulation

In this paper, the heat treatment of alumina fiber was studied. The infiltration agent on the fiber surface was removed after heat treatment at 450 °C for 6 h. TG-DSC, scanning electron microscope, x-ray diffraction, Fourier infrared spectrometer, energy dispersive spectrometer, and patterning were used to analyze the thermal weight loss, fiber surface morphology, crystal structure, and composition of alumina fibers. The results show that the aluminum oxide fiber has excellent temperature resistance and does not undergo crystal phase transformation during thermal weight loss. After heat treatment, the fiber surface infiltration agent ablates and dissolves from the fiber surface, and the internal crystal structure of the fiber remains stable. The tensile testing machine was utilized to test the breaking strength of alumina fiber. The fiber still maintained high strength after heat treatment, and the retention rate of breaking strength was greater than 74%. ZC-90G high insulation resistance measuring instrument and WDY-Ⅱ automatic voltage tester were utilized to analyze the insulation resistivity and breakdown strength of alumina fiber before and after heat treatment. The results show that heat treatment can effectively improve the insulation performance and breakdown strength of alumina fiber.

Characterization of wood fiber insulation for the development of wood fiber-insulated panels (WIPs) for use in building envelope

Wood fiber insulation (WFI) was studied as an eco-friendly alternative for fossil-based building insulation, focusing on its use in new wood fiber-insulated panels (WIPs). Rigid WFI boards with densities of 110, 140, and 180 kg/m³, including a 140 kg/m³ variant without paraffin wax, were evaluated. Key properties investigated included porosity, water vapor transmission, liquid water adsorption, and thermal conductivity. The porosity ranged between 85 and 92%, primarily influenced by density. Water vapor permeability ranged from 65 to 90 ng·s-1m-1Pa-1, while liquid water absorption was between 2.5 and 20% by volume, influenced by both wax and density. The thermal conductivity coefficient ranged from 0.038 to 0.055 W/(m·K). Bond strength tests with WFI (140 kg/m³ with wax) laminated to various materials using structural adhesives showed tensile perpendicular-to-grain strengths of 10 to 16 kPa and shear strengths of 60 to 90 kPa, with failure only occurring within the WFI. It was concluded that WFI is a promising material for novel WIPs, offering competitive hygrothermal properties and compatibility with structural adhesives. However, its bio-based nature suggests variability and complexity, necessitating further rigorous testing in various climates and in more complex assemblies.

Shrinkage characteristics of glass and mineral fibre insulation materials at elevated temperatures

The fire resistance of building assemblies can be determined through testing or by numerical modelling. As testing of building assemblies is expensive and time-consuming, the development of numerical modelling methods is gaining momentum. One of the challenges in modelling assemblies’ thermal performance is insulation dimensional shrinkage at elevated temperatures. To address this challenge, this paper presents a comprehensive experimental investigation into the shrinkage of glass and mineral fibre insulation materials under elevated temperature conditions. Initially, a series of tests was conducted to establish the temperature range within which significant shrinkage occurs for both types of insulation. Then, visual observations and measurements were recorded to assess the physical and dimensional changes of the insulation materials within the identified temperature range for shrinkage, indicating distinct responses of glass and mineral fibre insulation to thermal exposure. Compared to width and length variations, thickness reduction in insulation was more significant. Overall, the insulation thickness decreased as the exposed temperature increased. The glass fibre insulation completely melted at 710°C, while mineral fibre insulation disintegrated at 1000°C. In addition, empirical equations were derived to assess the thickness variations of these insulations at elevated temperatures, which can greatly enhance the accuracy of future thermal models under fire scenarios. Lastly, potential areas for future research are identified.

Development of a Predictive Model for the Thermal Conductivity of Natural Fiber Insulation: A Novel Approach for Quality Control

ABSTRACT Natural fiber insulation materials can offer a sustainable alternative to mineral and petrochemical-based insulation materials when suitable raw materials and appropriate production processes are considered. Within the scope of our research, natural fibers like cotton, flax, hemp, wool, and coir, as well as regenerated cellulose fiber, were processed into insulation materials and examined concerning their thermal conductivity. We demonstrate that simple test methods for fiber fineness measurement with air-flow methods such as Airflow and Shirley can facilitate incoming inspection and process monitoring for insulation manufacturers. Based on these measurements, a simple model was developed to estimate the thermal conductivity based on the fineness measurements of the raw materials. The model developed on the natural fibers for lower densities was tested on a glass fiber insulation material to check its suitability. The slight deviations achieved between the experiment and the calculation verify the practicability of the concept.

Performance Assessments of Direct Contact Serpentine Tube Based Photovoltaic Thermal Module: An Experimental Comparison

Solar energy is the most focused in the field of renewable energy. It is a clean, green, environmentally friendly energy source. One of the modern technologies utilized by researchers to investigate the wasted heat by the photovoltaic module is the photovoltaic thermal collector, which simultaneously provides thermal and electrical power for various engineering applications. This study presented a new configuration of a water-cooled photovoltaic thermal module that utilizes a copper serpentine tube attached directly using thermal silicon to the poly-crystalline PV module for water circulation. The created PV/T was well-insulated using fiber material, insulation cork, and Wooden parts. The water flow was circulated via a DC pump with low power consumption. The fabricated unit was compared to the standalone photovoltaic module for the performance evaluation. The main result showed a significant enhancement in the electrical productivity of the photovoltaic thermal module compared to the standalone unit. The cell temperature was reduced by 13.3% compared to the standalone photovoltaic module. Accordingly, the water-based PV/T module effectively eliminated the heat dissipated to the surrounding region by the PV module by using a serpentine tube, assuring sustainable contribution.

Porous (Y0.25Ho0.25Yb0.25Lu0.25)2Si2O7: A novel high‐entropy ceramic with high porosity and excellent thermal stability

AbstractWith the rapid development of hypersonic vehicles, the thermal protection systems face great challenges due to the severe aerodynamic heat. As a result, conventional fiber insulation tiles would experience severe shrinkage at high temperatures (&gt;1500°C), endangering the safety of the aircraft. To solve the problem, a high‐entropy effect was introduced to increase the high‐temperature resistance of thermal insulation materials, and highly porous (Y0.25Ho0.25Yb0.25Lu0.25)2Si2O7 was prepared by in situ reaction sintering process in this work. The fabricated porous samples present excellent overall properties, including superhigh porosity (95.09%–93.10%), lightweight (0.29–0.41 g/cm3), and very low thermal conductivity (0.066–0.085 W/(m·K)). More importantly, porous (Y0.25Ho0.25Yb0.25Lu0.25)2Si2O7 has outstanding high‐temperature dimensional stability. Although the porosity of the sample is higher than 90%, its linear shrinkage at 1550°C for 2 h is less than 1%. The results demonstrate that porous high‐entropy (Y0.25Ho0.25Yb0.25Lu0.25)2Si2O7 is a promising thermal insulation material in extreme high‐temperature environments.

Investigation on the flow and thermal properties of fibrous insulation used in thermal batteries at alternative atmosphere and pressure gradient

The accurate prediction of behavior for insulations within thermal battery can be impeded due to the fact that the thermal properties of insulations have not been thoroughly characterized under the complex conditions in which they operate. In this study, an effective and extendible model is developed based on fractal theory and finite element method to predict the flow and thermal properties for fibrous insulations within thermal batteries. Two common fibrous insulations are tested and verified with this model under the operating gas atmosphere of thermal battery. It is found that the predictive permeability and effective thermal conductivity agree well with the existing experimental data. Verification under various gas atmosphere shows that present model can reduce the relative error of existing model by 5.21–17.2 %. The gas contributed thermal conductivity for insulations filled with high thermal conductivity gas is always significant. In addition, under the tested pressure gradients, the deviations of temperature are generally greater than 1.42 % for air, methane and carbon dioxide atmosphere, but less than 0.7 % for hydrogen atmosphere. The high porosity of material, the large or reverse pressure gradient may strongly promote the influence of the energy migration within insulations.

Assessing the opportunity for producing hemp-based insulation in the Australian market

By-products (wastes or residues) of renewable materials have the potential to be manufactured into higher value fibre insulation products for the Australian market. Currently, such products have been imported for servicing the Australian market. This presents a potential opportunity to divert considerable quantities of waste from landfill and produce a high performance, locally made, low carbon, natural fibre insulation product for the Australian domestic and commercial building industry. This article assesses the hemp-based bulk insulations available in the Australian market.

Bio-based innovations in cross-laminated timber (CLT) envelopes: A hygrothermal and life cycle analysis (LCA) study

The purpose of this study is to evaluate the performance of a Cross-Laminated Timber (CLT) building envelope that employs more bio-based materials, in terms of its hygrothermal behavior and environmental impact. The study involved the construction of four wall assemblies, comparing the effects of the installation of a self-adhesive air barrier on the CLT and the choice of insulation: bio-based wood fiber insulation or stone wool insulation. The walls were subjected to static and dynamic tests in a climate chamber, with temperature and relative humidity sensors installed across the walls. Additionally, the life cycle analysis (LCA) of the identical assemblies was calculated using the Ecoinvent 3.5 database.The findings of the study showed that the wood fiber insulation had a lower relative humidity and a temperature similar to the stone wool insulation. The air barrier reduced the transfer of moisture and increased the temperature across the wall. Furthermore, the wood fiber insulation acted as a moisture buffer, thereby delaying the migration of moisture through the envelope. Concerning the LCA, the metal siding had the highest global warming impact, followed by the insulation types. The wood fiber insulation had a similar impact to the stone wool insulation, except for eutrophication, where stone wool had a lower impact. The air barrier had a negligible impact compared to the rest of the envelope but prevented the CLT wall from being fully recycled. The biogenic carbon stored in the CLT and the wood fiber insulation reduced the global warming potential of the walls.

Radiation heating tests to evaluate low-emissivity porous ceramics coatings for stand-off thermal protection systems

Diffuse reflection of thermal radiation transfer by Mie scattering can provide a thermal barrier without conversion leading to conduction heat transfer. Applying such a system to internal thermal insulating materials of a stand-off thermal protection systems (TPS) provides an efficient means of preventing thermal radiation transfer. Porous MgAl2O4 ceramics have high thermal resistance because of their low radiation absorption over a wide range from visible to near-infrared wavelengths. For this study, after porous MgAl2O4 ceramics was coated onto a fibrous insulator surface, we investigated its application to stand-off TPS, especially targeting reusable space transportation systems. Direct infrared heating tests were conducted in vacuum. Indirect infrared heating tests were done using graphite as a surface panel in an arc-heated wind tunnel with a high heat flux rate. The apparent thermal conductivity was obtained from the unsteady-state thermal history of the infrared heating experiment using an arc-heated wind tunnel to evaluate the radiation thermal barrier effects of the porous MgAl2O4 ceramics. The low emissivity of porous MgAl2O4 ceramics suppressed heat input and maintained a low surface temperature. Results suggest that thermal radiation transfer was suppressed and that the apparent thermal conductivity of the fibrous insulator was reduced.

Pore structure characterization and effective thermal conductivity modeling of fibrous building thermal insulation materials based on X-ray tomography

The existing structural characterization methods of building materials as well as thermal conductivity calculation models can not be directly applied when considering fibrous building thermal insulation materials with intricate skeletons. In this study, rock wool is considered the research object, and the X-ray tomography method is used to characterize the pore structure and extract structural parameters. Based on the actual pore morphology of the material, the pores in the representative elementary volume (REV) are reasonably assumed to be cubic. Additionally, considering the contact thermal resistance of fibers and the randomness of pore distribution, the curved pattern of heat conduction pathway with the ever-changing diameter is reasonably simplified into a series-parallel form of the curved heat chain with the same diameter. On this basis, the fractal models of effective thermal conductivity are established in horizontal and vertical directions. Finally, a modified formula for the effective thermal conductivity calculation of fiber thermal insulation materials is proposed, taking into account the influence of fiber orientation on the material thermal conductivity. It was shown that the relative deviation between the calculated correction value and the experimental value of the effective thermal conductivity is all less than 16.13%.

Examining the combustion hazards of polyacrylonitrile-based stabilizing fiber insulation with cellulose adhesive

Examining the combustion hazards of polyacrylonitrile-based stabilizing fiber insulation with cellulose adhesive

Study of basalt/hemp fibers reinforced B4C nanoparticles influenced hybrid epoxy composite: a novel approach for optical fiber insulation

Study of basalt/hemp fibers reinforced B4C nanoparticles influenced hybrid epoxy composite: a novel approach for optical fiber insulation

Predictive radiation heat transfer modeling in fibrous insulation at high temperature

The modeling of heat transfer in fibrous materials is important for designing and improving thermal insulation systems. At high temperatures and low sample density, thermal radiation is expected to be the primary mode of heat transfer in fibrous insulation. Currently, the most common and successful models for modelling heat transfer in insulation at high temperatures require the use of semi-empirical methods. The main limitation of this approach is that the model parameters need to be determined from thermal measurements for each possible material and re-determined if the morphological structure is modified, even for the same material. This paper presents a predictive model for radiation heat transfer based solely on physical and morphological properties. The model was validated using experimental determinations of the effective thermal conductivity in a low-density alumina-based insulation. The model demonstrates good agreement with experimental measurements, and its predictions fall within the experimental uncertainty limits for temperatures between 800 K and 1700 K.

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

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

Effect of Applied Pressure on the Performance of Biodegradable Fiber Insulation Board Manufactured from Camphor Branches (Cinnamomum camphora)

Currently, the predominant thermal insulation materials in the construction industry are primarily derived from inorganic sources. While these materials demonstrate commendable thermal insulation capabilities, their widespread use raises significant environmental concerns. The utilization of wood fiber materials presents a promising solution to mitigate these drawbacks. This study focuses on the fabrication of biodegradable fiber insulation board (BFIB) using camphor branches. The manufacturing process avoids the use of chemical additives, employing a physical method that utilizes hot pressing and relies on the formation of intermolecular hydrogen and hydroxide bonds between the fibers. The study evaluates the influence of applied pressure on the properties of BFIB. SEM images reveal that, with an increase in applied pressure, the fibers exhibit a more regular pattern, subsequently enhancing the mechanical properties, hygric behavior, and fire resistance properties of BFIB. As an environmentally friendly and renewable material, BFIB holds the potential to substitute conventional insulation materials. It is particularly intriguing for energy-saving purposes when applied as building insulation for walls or ceilings.