Rigid Insulation Research Articles

Preparation and properties of a rigid hemp shiv insulation particle board using citric acid-glycerol mixture as an eco-friendly binder

Particle boards are commonly manufactured from wood-based material bound with a thermosetting adhesive based on the reaction of formaldehyde with phenol, urea, melamine, or co-condensates. The use of formaldehyde is a cause for concern due to its harmful emissions. This study investigates the use of an alternative binder combined with particles derived from a short-cycle crop as an alternative to timber derived particles. A low density particle board was developed using hemp shiv as an aggregate with a binder made with crude glycerol, derived from the waste stream of the bio-diesel industry, esterified with citric acid under heat activation. This board was characterized and found to have good mechanical properties, low thermal conductivity, and good moisture buffering. Dimensional stability was compromised by swelling when exposed to water, but it will be possible to address this shortcoming using hydrophobic additives. The acoustic properties of the board were also found to be excellent, showing potential for use as a thermally insulating acoustic separator for internal walls.

Properties of Binderless Insulating Boards Made from Canary Island Date Palm and Cork Particles

Agglomerated cork is a natural cork that has gone through a process of crushing and pressing using heat and binders. One of its applications is thermal insulator in construction. The design of these materials is becoming an essential part of building. The raw materials currently used to make insulators consume a large amount of energy, which has created the need to increase the use of renewable and ecological resources such as plant fibers to reduce the environmental problems generated. The objective of this study was to determine the different properties of experimental particleboard panels made from cork and Canary Island date palms without using any binder at minimum energy consumption. The produced cork–palm boards (density of 850 kg/m3, reached a MOR 8.83 N/mm2, MOE 794.5 N/mm2, and IB 0.38 N/mm2) are higher values than the traditional cork particleboards with UF made from cork. The thermal conductivity values obtained 0.069 to 0.096 W/m·K are higher than cork boards with UF. Ecological boards that can be used as rigid thermal insulators in the construction industry have been achieved to improve the mechanical properties of the traditional agglomerated cork.

Experimental Investigation of the Mechanical Behavior of the Strain Isolation Pad in Thermal Protection Systems under Tension

A strain isolation pad is a critical connection mechanism that enables deformation coordination between the rigid thermal insulation tile and the primary structure in the thermal protection system of a reusable hypersonic vehicle. An experimental investigation has been conducted to determine the static, loading–unloading, and high-cycle fatigue (HCF) responses of the SIP with 0.2 mm adhesive under through-thickness tension at room temperature. The contributions of the rigid thermal insulation tile and metallic substructure have not been considered so far. The results indicate that the tensile behavior of the SIP joint is highly nonlinear. The static and fatigue tensile failures both initiate from the corner close to the adhesive/SIP interface due to the stress concentration and the edge effect. The uniform breakage of the aramid fiber can be seen on the cross-section. A novel method is proposed to quantify the residual strain due to the short-time ratcheting effect of the SIP joint in the initial loading–unloading tensile response. As the number of fatigue cycles increases, the thickness of the SIP joint continues to increase until failure. An explicit expression associated with the growth of SIP joint thickness, fatigue cycle number, and peak cyclic stress is established. The turning point of the thickness growth rate with the fatigue cycle number is proposed as a new fatigue failure index for the SIP joint under tensile fatigue, and a fatigue life prediction model is developed.

Transit-oriented development: A case study of exterior-to-interior noise control for buildings near transit and highway noise sources

A case study of acoustical design for mixed-used, transit-oriented development is presented. The project is two, six-story mixed-used residential buildings near a rapid transit station and heavily traveled elevated highway in the San Francisco Bay Area. The buildings are metal frame construction over concrete podiums. The California Building Code requires the building shell to be designed to provide interior noise from exterior noise sources not to exceed 45 dBA Ldn. Exterior noise due to trains and buses serving the transit station, and traffic on the elevated highway, required high sound attenuating windows and acoustically rated walls and roofs. Initially, none of the exterior wall assemblies included batt insulation in the stud cavities, only continuous rigid insulation behind the façade. Modeling was done to compare the exterior wall assemblies with and without batt insulation in the stud cavities combined with various window configurations. Estimates of the building shell transmission loss are presented along with a summary of noise control recommendations for building roof, windows, and doors.

Investigations on tensile mechanical properties of rigid insulation tile materials at elevated temperatures based on digital image correlation algorithm

This work investigates the tensile mechanical properties of rigid insulation tile (RIT) materials at room temperature (26 °C) and elevated temperatures (700–1000 °C) through experimental and digital image correlation (DIC) methods. Experimental results indicate that the tensile strength of RIT materials changes nonlinearly with increasing temperature and that the primary fracture mode under tension load is fiber root fracture. In terms of the DIC algorithm, this work builds an elevated-temperature DIC test system. A zero-mean Gaussian filtering algorithm and an image gradient difference square sum algorithm (SSDGI) are proposed to improve the precision of the DIC algorithm. The derived tensile stress-strain curve of RIT materials reveals that the elastic modulus changes nonlinearly with increasing temperature. The reliability and precision of the DIC algorithm are confirmed through the tensile test of silicon carbide particle-reinforced aluminum matrix composites. Hence, this work provides guidance for evaluating mechanical properties of RIT materials under elevated temperature environments.

High Emissivity MoSi2-SiC-Al2O3 Coating on Rigid Insulation Tiles with Enhanced Thermal Protection Performance.

High emissivity coatings with sol as the binder have the advantages of room temperature curing, good thermal shock resistance, and high emissivity; however, only silica sol has been used in the current systems. In this study, aluminum sol was used as the binder for the first time, and MoSi2 and SiC were used as emittance agents to prepare a high emissivity MoSi2-SiC-Al2O3 coating on mullite insulation tiles. The evolution of structure and composition at 1000-1400 °C, the spectral emissivity from 200 nm to 25 μm, and the insulation performance were studied. Compared with the coating with silica sol as a binder, the MoSi2-SiC-Al2O3 coating has better structural uniformity and greater surface roughness and can generate mullite whiskers at lower temperatures. The total emissivity is 0.922 and 0.897, respectively, at the wavelength range of 200-2500 nm and 2.5-25 μm, and the superior emissivity at a low wavelength (<10 μm) is related to a higher surface roughness and reduced feature absorption. The emissivity reduction related to the oxidation of emittance agents at a high temperature (-10.2%) is smaller than that of the silica-sol-bonded coating (-18.6%). The cold surface temperature of the coated substrate is 215 °C lower than the bare substrate, suggesting excellent thermal insulation performance of the coating.

Cyclic Lateral Loading Behavior of Thin-Shell Precast Concrete Wall Panels

Two precast concrete thin-shell wall panels were subjected to reverse-cyclic lateral loads to replicate wind fatigue over a 50-year design lifetime prior to loading to failure. The panels consisted of an outer wythe of concrete connected to light-gauge steel framing. Wire mesh was used to reinforce the concrete panel skin. Rivets provided a connection between the steel studs and the concrete panel. Two reinforced concrete (R/C) beams were integrated into the top and bottom parts of the panel, isolated from the concrete face by a thin sheet of extruded polystyrene (XPS) foam insulation. To connect these beams with the concrete face through the rigid foam insulation, a carbon-fiber-reinforced polymer (CFRP) grid was utilized. The aim of the experimental program was to characterize the behavior of the concrete and steel framing panel, with particular attention focused on the connections between the various structural elements of the panel. The first and second thin-shell panels survived the fatigue loading cycles and behaved elastically through failure-level lateral load cycles equivalent to 54 psf (2.6 kPa) and 66 psf (3.2 kPa) of applied uniform load, respectively. The failure mode was the separation of the top R/C beam from the concrete panel on the pull stroke of the loading cycle (when the connection between the beam and the concrete shell was in tension) for both specimens.

Liquid hydrogen storage design trades for a short-range aircraft concept

Preliminary design trades for the liquid hydrogen storage system of a short-range aircraft are presented. Two promising insulation methods, namely rigid foam and multilayer insulation, are identified as main design drivers. In addition, the maximal pressure and the shape of the hydrogen storage tank influence the aircraft performance and the insulation efficiency. In this study, the hydrogen storage tanks are integrated in wing pods. The main effects driven by the design parameters are addressed using conceptual and preliminary methods: models are carried out for the storage mass, additional drag, propeller efficiency loss and the dynamical thermodynamic behavior of the liquid hydrogen storage. These effects are coupled making an integrated design method necessary. For the sizing of the liquid hydrogen storage, a multidisciplinary workflow is set up including the aircraft sensitivities on the design mission block fuel. The trade-off study reveals the opposing trend between insulation efficiency and aircraft performance. For the insulation architecture based on rigid foam, the penalties implied by the storage tank on aircraft level and the penalties due to vented hydrogen can be balanced and result in minimal block fuel for the design mission. The application of multilayer insulation avoids venting during the design mission, but has an increased penalty on the aircraft performance compared to rigid foam insulation. Besides the criterion of minimal block fuel, the dormancy time is compared, indicating the thermal efficiency. Applying multilayer insulation, the dormancy time can be increased significantly calling for a discussion of operational requirements for hydrogen-powered aircraft.

VOC Emission from Lightweight Wood Fiber Insulation Board

The aim of the presented research work was to determine and analyze emissions of volatile organic compounds (VOCs) from experimental lightweight wood fiber insulation board produced in dry technology. Until now, there have been no rigid insulation materials made of wood fibers produced in such low density and made in dry technology. Among the typical parameters such as thermal conductivity and the mechanical performance of the lightweight board, attention was also paid to their influence on indoor air quality. Therefore, an attempt was made to determine the kind of substances emitting from wood fiber insulation boards produced at defined production parameters as well as the dynamics of emission reduction over time. Additionally, the influence of fire retardants used for protection against lightweight wood fiberboard fires on the emission of VOCs was analyzed. Tests on VOC emissions were carried out using the chamber method according to the applicable ISO 16000 standards. The main components emitting from lightweight insulation fiberboards were acetic acid and aldehydes such as pentanal, hexanal, heptanal, octanal, nonanal, decanal, furfural, and benzaldehyde. The percentage of acetic acid in total volatile organic compounds (TVOCs) was within the limits of 17% to 65%. From the aldehydes group, the most concerning substance was furfural due to a very strict limit value. In the presented research, depending on the variant, the emission of furfural was from 0 up to 10 µg/m3 after 28 days of measurement. Other substances such as terpenes or aromatic hydrocarbons were at a very low level. The reduction in VOCs over a period of 28 days was significant in most cases from 22% up to 61%. The tests carried out also showed a substantial impact of fire retardant, used in the production of lightweight insulation fiberboard, on the emission of VOCs from fiberboards, and thus on their quality.

A review on the various factors influencing the structural behaviour of TRC sandwich elements

This review article discusses the structural performance of Textile Reinforced Concrete (TRC) sandwich structures consisting of two outer TRC faces and a rigid core insulation. Sandwich structures offer advantages such as lightweight construction and thermal insulation. Hence, the application of the non-corrosive TRC as the facings of sandwich panels helps in reducing the overall thickness and weight of the panels by replacing the reinforced concrete faces and eliminating the thick concrete cover. The strength, stiffness and load-carrying capacity of TRC sandwich panels are governed by several factors such as thickness of the face, density of the core material, reinforcement ratio, the use of shear stiffeners, etc. In this review article, the influence of various parameters such as face thickness, type of textile, number of textile layers, core thickness and core density are addressed. The effect of shear connectors on enhancing the composite behaviour of TRC sandwich panels is also discussed.

Shear Transfer Mechanism between CFRP Grid and EPS Rigid Foam Insulation of Precast Concrete Sandwich Panels

An experimental program was implemented to investigate the shear transfer mechanism of carbon-fiber-reinforced polymer (CFRP) grids and expanded polystyrene (EPS) rigid foam insulation in three wythe precast concrete sandwich wall panels. The purpose of the research was to measure the shear flow capacity and to observe the failure mode(s) of precast concrete sandwich panels manufactured with a CFRP grid shear transfer mechanism between wythes. Six precast concrete sandwich panels were examined by push-out tests in which the center concrete wythe was pushed downward with respect to two outer concrete wythes. It was observed that the average shear flow capacity of the specimens having 2 in (51 mm) thick foam was higher than that of the specimens having 4 in (102 mm) thick foam. In addition, stiffness decreased significantly when the thickness of the EPS insulation increased. The failure mode for the panels included relative displacement between the center concrete wythe and the outer concrete wythes. Test results showed that panels tended to fail by CFRP grid rupture, CFRP grid pull-out, and loss of bond at the concrete/foam interface. Further tests should be performed to fully comprehend the nature of the shear transfer mechanism between the specific CFRP grid used and EPS rigid foam insulation.

Improving the quality of rigid polyurethane foam sandwich insulation panels

Improving the quality of rigid polyurethane foam sandwich insulation panels

Mechanical and dual-stage wind tunnel ablative behavior of ceramic fiber-tile reinforced phenolic aerogel

This paper reports a porous organic-inorganic mixed thermal protection composite served in a high-temperature long-term environment. The rigid ceramic thermal insulation tile (CIT) reinforced phenolic aerogel (PR) composite has good mechanical properties, thermal insulation, and ablation resistance. The maximum linear thermal expansion coefficient was 4.707 × 10−6, and compressive strength and modulus reached 4.56 and 70.88 MPa, respectively. The thermal conductivity was 0.041 W/(m·K) at room temperature. After two-stage wind tunnel ablation at a high temperature exceeding 1300 °C for 270 s and a low temperature exceeding 800 °C for 180 s, the backside temperature was 242 °C. The ablation behavior and transformation process in the thickness direction were analyzed. The porous organic-inorganic mixed composite has a great prospect in long-term near-air flights.

Investigation of a novel insulation foam made from gypsum drywall waste

Foamed plastic rigid insulation panels are effective for reducing building heating and cooling loads, with consequent reductions in energy use and associated greenhouse gas (GHG) emissions. However, plastic foam manufacturing and in-service use result in significant GHG emissions. In addition, plastic foams are flammable, and have been implicated in recent building fires. This paper describes proprietary mixtures and methods for producing drywall waste foam (DWF) panels, a carbon-neutral, fire-protective insulation made from gypsum drywall waste and other construction and demolition (C&amp;D) waste materials. Gypsum drywall waste is inherently fire-protective and has relatively low thermal conductivity, but is a low-value commodity with few current reuse and recycling applications. DWF panels address two pressing issues in the built environment: decarbonization of building materials, and diversion of problematic C&amp;D waste from landfills. Investigation of DWF panel engineering properties, including density, hardness, friability, burn-through time, and thermal conductivity are reported, with results compared to analogous commercially-available materials. Potential applications and areas for future investigation are also discussed.

Experimental performance evaluation of a novel design solar desalination device equipped with air stones

The increasing need for a freshwater supply has led researchers to suggest improved solar stills as one solution to the problem of water shortages. For this purpose, to cover the maintenance and performance gap in this field, three enhancement techniques, including rigid PVC boxes, sliding absorber plates, and air stones at different water depths, are tested in the solar stills. The highest daily production and efficiency for rigid PVC insulation boxes (case A) were about 23 % and 7.6 % more than the conventional solar still and more proper than many previous studies. The maximum daily production and efficiency of an improved solar still with air stones (case B) with water depths of 2 have been 4192 mL/m2 and 42 %, respectively. The daily production of case B with a water depth of 2 cm and air stone lengths of 0.1 m, 0.3 m, and 0.55 m was 22.6 %, 27.6 %, and 34.7 % higher than the conventional one. By comparing the cost per litre (CPL) of the conventional and improved solar stills, it was observed that the CPL in cases A and B was 0.013 $/L and 0.016 $/L, which was about 16 % lower and 11 % higher than a conventional still, respectively.

Alternatives derived from renewable natural fibre to replace conventional polyurethane rigid foam insulation

There is an exponential rise in the use of non-biodegradable Rigid Poly Urethane (RPU) foam insulation, creating a significant concern for the environment. Greener alternatives to RPU insulation are underexplored and need the hour to unveil newer dimensions in plant material added insulation research. We have discussed three alternative technologies involving raw material from plant sources and potentially replacing RPU foam. Renewability and greater bio-degradability are the key benefits of these technologies in combating the environment-related challenges offered by 100% RPU Insulation. This review has discussed the resultant changes in the foam developed from plant-based polyol replacing the petroleum-based polyol in terms of physical and morphological properties, also the resultant effect of natural fiber reinforcement of PU matrix on the thermal, tensile, and biodegradable properties. This paper has analyzed natural fiber-based nonwoven fabric composites with excellent insulation properties from the mechanical strength and environmental impact reports. We made a critical comparison between the three technologies. Finally, the paper has identified the scope of future research to validate the claim of suggested alternatives for commercial-scale applications.

Condition assessment of concrete plates using impulse-response test with affinity propagation and homoscedasticity

This article presents a procedure based on the impulse-response test and the affinity propagation algorithm to detect delamination, honeycomb, and debonding in concrete slabs. Frequency response functions (FRFs) generated with the impulse-response test according to the protocols of ASTM C1740 on a grid pattern are combined to define a feature space matrix. The affinity propagation (AP) algorithm is used to cluster the FRFs sharing similar features. Clusters are shown to correspond to either intact locations or defects and cluster membership can be used to locate defects in the slab. The effectiveness of the algorithm for defect delineation depends on the optimal number of exemplars and some objective criteria to categorize each cluster according to the severity of defects. To achieve this objective, an upper bound for the number of exemplars is proposed based on the number of principal components explaining most of the percent variance in the feature matrix for optimal defect detection and the variance of the FRF is proposed and validated as a criterion for ranking the severity of defects. Homogeneity of variance testing is used for merging exemplars that exhibit similar levels of variability to address potential overfitting associated with the AP algorithm. Two fully supported slabs with free edges and having different simulated defects, and a slab cast on a rigid insulation board with delamination and honeycomb are used to validate the proposed procedure. The proposed procedure is shown to efficiently detect shallow delaminations and debonding. The deep delamination and honeycomb in the slabs were delineated but to a lesser extent compared with the shallow delamination.

Studying the Suitability of Nineteen Lignins as Partial Polyol Replacement in Rigid Polyurethane/Polyisocyanurate Foam.

In this study, nineteen unmodified lignins from various sources (hardwood, softwood, wheat straw, and corn stover) and isolation processes (kraft, soda, organosolv, sulfite, and enzymatic hydrolysis) were used to replace 30 wt.% of petroleum-based polyol in rigid polyurethane/polyisocyanurate (PUR/PIR) foam formulations. Lignin samples were characterized by measuring their ash content, hydroxyl content (Phosphorus Nuclear Magnetic Resonance Spectroscopy), impurities (Inductively Coupled Plasma), and pH. After foam formulation, properties of lignin-based foams were evaluated and compared with a control foam (with no lignin) via cell morphology, closed-cell content, compression strength, apparent density, thermal conductivity, and color analysis. Lignin-based foams passed all measured standard specifications required by ASTM International C1029-15 for type 1 rigid insulation foams, except for three foams. These three foams had poor compressive strengths, significantly larger cell sizes, darker color, lower closed-cell contents, and slower foaming times. The foam made with corn stover enzymatic hydrolysis lignin showed no significant difference from the control foam in terms of compressive strength and outperformed all other lignin-based foams due to its higher aliphatic and p-hydroxyphenyl hydroxyl contents. Lignin-based foams that passed all required performance testing were made with lignins having higher pH, potassium, sodium, calcium, magnesium, and aliphatic/p-hydroxyphenyl hydroxyl group contents than those that failed.

Investigation of the impact of a particle foam insulation on frost buildup on the aircraft structure

The aircraft insulation separates the thermally comfortable cabin interior environment from the extremely cold outside condition. However, the fabrication and installation of the insulation in the aircraft is a labour intensive task. Tailored, rigid particle foam parts could be a solution to speed up installation process. The presented study investigates the feasibility of such a concept from a hygrothermal point of view. Due to the temperature difference between the cold air trapped between aircraft skin and insulation on one side and the warm cabin air on the other side, a buoyancy induced pressure difference forms. This effect drives the warmer air through leakages in the insulation system towards the cold skin. Here, moisture contained in the air condenses on the cold surfaces, increasing the risk for uncontrolled dripping (“rain in the plane”) when it melts. Therefore, this study compares the frost build-up of different installations of a rigid particle foam frame insulation with the classical glass fiber capstrip. Tests are hosted in the Fraunhofer Lining and Insulation Test Environment chamber.

Building-Information-Modelling-Based Thermal-Energy Performance Evaluation of Silica-Aerogel-Incorporated Rigid Board Roof Insulation Material for Residential Buildings in the Tropical Climate of Malaysia

Malaysia is located in the equator, with a hot and humid climate. The highest temperature recorded during the day was 39 °C, which leads to discomfort among building occupants, in particular, residential buildings, where indoor thermal comfort is of a higher priority compared to other types of buildings. Hence, the thermal performance of the residential roof assembly needs to be improved to lower the indoor temperature and, accordingly, maintain the level of indoor thermal comfort. In view of the need to improve the thermal performance, a silica-aerogel-incorporated rigid board roof insulation material for residential buildings was developed using kapok fibre, high density polyethylene (HDPE) and silica aerogel. The thermal conductivity of the material was measured. The sample with 4 wt. % and 5 wt. % of silica aerogel content obtained the lowest thermal conductivity of 0.04 W/mK. Silica aerogel content of above 4 wt. % did not result in further reduction of the thermal conductivity. Therefore, it can be concluded that the optimum silica aerogel content for the sample was 4 wt. %. Building-Information-Modelling (BIM)based thermal-energy performance evaluation of the material was performed by generating temperature and cooling load data using Integrated Environmental Solution-Virtual Environment to validate the thermal-energy performance of the material, by installing the material within the roof assembly of a residential BIM. Findings indicate that the material can potentially be employed in the future as a roof insulation material to maintain the level of indoor thermal comfort among residential building occupants.