Search Results (51)

A method has been developed to delaminate the organic components (paint, foam) from the steel skins of composite polyisocyanurate (PIR) steel insulation panels at ambient temperature and in 20 min using selected solvents combined with ultrasonication. Using this method, polyisocyanurate foam can be selectively delaminated from polymer-based paint (PVC plastisol) and, in turn, the polymer paint can be selectively delaminated from the galvanised steel. Both the foam and paint are removed as intact layers, leaving the galvanised steel intact for the next steps of recycling, enabling the subsequent individualised recycling of each sub-component or layer. Several solvents have been tested, and the data show that H-bonding solvents (e.g., H₂O, alcohols) are less effective at delaminating these polymers. Whilst high polarity, medium H-bonding acetonitrile and DMSO remove PVC paint and some PIR foam, the most effective solvent for both PIR foam and PVC paint removal is medium polarity, medium H-bonding acetone. Full article

Rigid polyurethane (PUR) and polyisocyanurate (PIR) foams are widely used as thermal insulation materials due to their excellent thermal conductivity and low density. However, fire resistance remains a critical property determining their safe application in construction, transportation, and energy systems. This study provides a comparative overview of the fire behavior of PUR and PIR foams, focusing on structural aspects, decomposition mechanisms, flame retardancy, and performance of emission of toxic gases during the combustion process. Despite extensive studies on PUR and PIR foams, systematic comparative investigations addressing the combined influence of recycled PET-based polyester polyols, isocyanurate content, and fire-related properties—including thermal degradation, heat release, and toxic gas emissions—remain limited. PIR foams, characterized by higher isocyanate indices and the presence of isocyanurate rings, show superior thermal stability, reduced heat release rates, and enhanced char formation compared with PUR foams. Experimental analysis of thermal degradation (TGA/DTG) and heat release (cone calorimetry) confirms that PIR foams demonstrate higher resistance to ignition and slower fire propagation. The results emphasize the critical role of molecular architecture and crosslink density in shaping the fire performance of rigid foams, highlighting PIR systems as advanced insulation solutions for applications requiring stringent fire safety standards. The PIR foam was prepared using a polyester polyol derived from recycled PET, which could help in achieving better fire properties during the combustion process. Compared with PUR foams, PIR foams exhibited an approximately 50% reduction in peak heat release rate, an increase in char yield from about 3 wt.% to over 22 wt.%, and a shift of the main thermal degradation peak by approximately 55 °C toward higher temperatures, indicating substantially enhanced fire resistance. Full article

Mycelium-based composites (MBCs)—biomaterials made from fungal-inoculated substrates—are promising candidates to replace conventional rigid thermal insulation panels. However, many MBCs are made from hemp, a plant material that is quite difficult to source in many countries for regulation reasons, and mobilizes agricultural fields at the expense of food and feed crops. Meanwhile, many of our natural and urban ecosystems are subject to invasion by plants that are just burnt or even left in place, while they may be very good substrate for MBCs. This study investigated the comparative physical and thermal properties of MBCs derived from two distinct lignocellulosic feedstocks: hemp shives (a traditional material) and biomass from the highly invasive species Reynoutria japonica. Polyisocyanurate (PIR) was included as a synthetic benchmark. The MBCs produced from R. japonica demonstrated as low a thermal conductivity as the hemp MBCs in our internally developed method, but also as the PIR standard. However, they exhibited suboptimal physical characteristics: higher bulk density (166 vs. 128 kg/m³ for hemp) and significantly higher water absorption (7.5% vs. 3.5% volume uptake after 2 min). This suggest that they are a less viable alternative to hemp-based MBCs for heat insulation applications. Full article

Myo-inositol (cis-1,2,3,5-trans-4,6-cyclohexanehexol) (In) was incorporated into rigid polyurethane/polyisocyanurate (PU/PIR) foams to investigate its effect on the degradation and performance properties of the foam, as well as its structure. The parameters studied included production temperature, processing times, strength, absorbency, and flammability. The foams were aged (degraded) in a special degradation chamber. The test results indicated the effect of myo-inositol on the foam properties. The addition of In caused a reduction in the cell diameter of the foams (measured in both directions). Absorptivity and water absorption decreased. The compressive strength of the foams increased and the flammability decreased (increased retention and decreased burning rate). As a result of foam degradation, the thickness of the degraded foam layer containing 13 wt.% myo-inositol (In13_D) increased by approximately 30% compared to the reference foam (In0_D). Full article

This study evaluates the impact of different flame retardants on the mechanical and thermal properties of rigid polyisocyanurate (PIR) foams, focusing on formulations with isocyanate indexes of 335 and 400. The flame retardants tested include triethyl phosphate (TEP), ammonium polyphosphate (APP), aluminium hydroxide (Al(OH)₃), and a combination of APP and Al(OH)₃. FOAMAT^® was used to analyse the foaming kinetics, while further tests assessed density, thermal conductivity, and compression strength. TEP, a liquid flame retardant, was found to reduce peak heat release rate (pHRR) and total heat release significantly, outperforming solid flame retardants. Although solid flame retardants like APP slightly increase start times and gel times due to their non-reactive, filler role, they increase the foam’s density and somewhat limit the effectiveness in reducing flammability. The uneven dispersion and lower compatibility of solid additives may lead to suboptimal improvements in fire resistance. APP displayed dual-phase decomposition, aiding char formation to a degree. Overall, TEP proved most effective in enhancing PIR foam’s fire resistance, demonstrating the advantage of liquid over solid flame retardants in achieving uniform distribution and better integration with the foam matrix, thus optimising thermal insulation and mechanical performance. Full article

This study investigates the use of a local fiber, specifically milkweed that grows in Quebec, Canada, for nonwoven building applications. Milkweed is a natural fiber with an ultra-lightweight hollow structure that provides excellent acoustic and thermal insulation properties. To provide three-dimensional stability to nonwovens, milkweed fibers were blended with a low-melt fiber composed of a polyethylene terephthalate core and a polyolefin sheath (LM 2.2), and polylactic acid (PLA) fibers. Several nonwovens with different fiber contents were manufactured using an air-laid Spike process. The nonwovens were compared with a commercially available thermal insulation material made of 100% hemp. The thermal conductivity and thermal resistance were measured at different temperatures. The sound absorption coefficient of the nonwovens was determined both using an impedance tube and the Johnson–Champoux–Allard (JCA) acoustic model. The results showed that all nonwovens exhibit thermal conductivity values below 70 mW/m·K at temperatures ranging from −4 °C to 24 °C, which are lower than many materials commonly used in building applications. A sample presented a thermal resistance that is 8%, 10%, and 45% higher than those of rock wool, polyisocyanurate (PIR), and fiberglass, respectively. Full article

Five series of rigid polyurethane–polyisocyanurate (RPU/PIR) foams were obtained. They were modified by ashes from burning paper (P) and wood: conifers (pine—S, spruce—S’) and deciduous trees (oak—D, birch—B). The ash was added to rigid polyurethane–polyisocyanurate foams (PU/PIR). In this way, five series of foams with different ash contents (from 1 to 9% wt.) were obtained: PP, PS, PD, PS’, PB. The model foam (reference—W) was obtained without filler. The basic properties, physico-mechanical, and thermal properties of the ashes and obtained foams were examined. It was specified, among other things, the cellular structure by scanning electron microscopy (SEM), and changes in chemical structure by Fourier-transform infrared spectroscopy (FTIR) were compared. The obtained foams were also subjected to thermostating in a circulating air dryer in increased temperature (120 °C) for 48 h. Ash tests showed that their skeletal density is about 2.9 g/cm³, and the pH of their solutions ranges from 9 to 13. The varied color of the ashes affected the color of the foams. SEM-EDS tests showed the presence of magnesium, calcium, silicon, potassium, aluminum, phosphorus, sodium, and sulfur in the ashes. Foam tests showed that pine ash is the most beneficial for foams, because it increases their compressive strength three times compared to W foam and improves their thermal stability. All ashes cause the residue after combustion of the foams (retention) to increase and the range of combustion of the samples to decrease. Full article

This study explores the optimization of rigid polyisocyanurate (PIR) foam formulations, focusing on foaming kinetics that significantly influence the foam’s microstructure and thermal insulation properties. By systematically altering components such as isocyanate, polyols, catalysts, blowing agents, and additives, this research investigates their effects on key characteristics including cell density, mechanical strength, and thermal conductivity. A statistical approach known as response surface modeling (RSM) was employed to identify relationships between formulation variables and performance metrics. The optimization aimed to enhance thermal insulation while ensuring feasibility for industrial-scale production, particularly for sandwich-type PIR panels. Two distinct formulations, with isocyanate indices of 335 and 400, were developed to assess the impact of various parameters on properties like foaming start time, gel time, and density. The results indicated that the choice of blowing agents and catalysts played a pivotal role in controlling foaming kinetics and final mechanical properties. The optimized formulations exhibited competitive thermal conductivity values (around 23.7 mW/(m·K)) and adequate compression strength (0.32 MPa), aligning closely with commercially available materials. These findings affirm the potential for enhancing production efficiency and performance consistency in the manufacturing of rigid PIR foams for insulation applications. Full article

In the present work, the influence of the addition of graphene nanoplatelets presenting different dimensions on polyurethane–polyisocyanurate aerogel structure and properties has been studied. The obtained aerogels synthesized through a sol–gel method have been fully characterized in terms of density, porosity, specific surface area, mechanical stiffness, thermal conductivity, and speed of sound. Opacified aerogels showing high porosity (>92%) and low densities (78–98 kg/m³) have been produced, and the effect of the size and content of graphene nanoplatelets has been studied. It has been observed that formulations with less than 5 wt.% of graphene nanoplatelets larger than 2 microns can effectively reduce the total thermal conductivity by absorption and scattering of the infrared radiation, reducing the heat transfer by this mechanism. The resulting opacified samples are highly insulating materials, with thermal conductivities less than 18 mW/m·K. Moreover, it has been observed that smaller particles with ca. 200 nm of average length can promote an increase in the elastic modulus, therefore obtaining stiffer aerogels, combined with thermal conductivities lower than 20 mW/m·K. Results have been studied in detail, providing a further understanding of the mechanisms for improving the final properties of these materials, making them more suitable for industrial applications. Full article

This article aims to assess the benefits of floor slab insulation measures using extruded polystyrene (XPS) and polyisocyanurate (also referred to as polyiso or PIR) insulation materials at various levels of insulation thicknesses for a detached residential building. An EnergyPlus simulation analysis was carried out within the seven energy zones (represented by eight locations) of South Africa in accordance with the South African national code for building energy efficiency (SANS10400-XA). The energy savings and payback periods related to the use of the insulation over a lifecycle period of 50 years were assessed. Cape Town (zone 4) behaved differently from other locations and hardly benefited from the application of floor slab insulation measures. Generally, polyiso (PIR) insulation performed better than XPS for vertical gap insulation, and lower insulation thicknesses required higher insulation depths to maximize energy savings. Similarly, lower insulation thicknesses (25 mm and 50 mm) required higher perimeter insulation widths to maximize energy savings for horizontal perimeter insulation, especially in Sutherland (zone 6) and Cape Town. The maximization of energy savings was also achieved at low insulation thickness for the full floor slab insulation method, except for Sutherland and Fraserburg (zone 7). The locations that benefitted most from the floor slab insulation methods were Pretoria (zone 5), Thohoyandou (zone 3), Sutherland (zone 6), Fraserburg (zone 7), Welkom (zone 1), Ixopo (zone 5H), Witbank (zone 2), and Cape Town (zone 4), in that order. Generally, higher net energy savings are achieved in areas with lower humidity levels and areas with greater annual sums of both cooling and heating degree days. Full article

Recently, there has been a growing interest in the use of sandwich panels that, beyond handling well-known bending stress, can withstand torsional stresses. This is particularly relevant for wall applications when the panels are equipped with photovoltaic or supplemental curtain wall modules. This research article presents a detailed exploration of the structural behavior of eccentrically loaded sandwich panels, with a specific focus on warping torsion. Experimental and numerical studies were conducted on polyisocyanurate (PU) core sandwich panels, commonly employed in building envelopes. These studies involved various dimensions and material properties, while omitting longitudinal joints. The experimental study provided essential insights and validated the numerical model in ANSYS. Enabling parametric variation, the numerical analysis extends the analysis beyond the experimental scope. Results revealed a high degree of correlation between experimental, numerical, and analytical solutions, regarding the rotation, as well as the normal and shear stress of the panel. Confirming the general applicability of warping torsion in sandwich panels with certain limitations, the study contributes valuable data for applications and design of eccentrically loaded sandwich panels, laying the foundation for potential engineering calculation methods. Full article

A deep understanding of the material parameters and the behavior of sandwich panels, which are used in the construction industry as roof and façade cladding, is important for the design of these construction components. Due to the constant changes in the polyurethane (PU) foams used as a core material, the experimental database for the current foams is small. Nowadays, there is an increasing number of failures of façade and roof panels after installation. This article presents a variety of experimental investigations on sandwich panels from two manufacturers with a core of polyisocyanurate (PIR) rigid foam (density: 40 kg/m³). As part of this study, compression, tension, shear, and bending tests were performed in several spatial directions and over the range required by the standard. The results of the tests showed the orthotropy of the core material and the dependence of the material on the direction and type of load. The stress-strain curves showed linear and non-linear areas. Using the data from this experimental study, a numerical model was implemented which utilized the Hill yield criterion to represent the orthotropy of the core material. The present investigation suggests that the classical von Mises failure criterion, used in many studies, is not suitable for the foam system applied in these sandwich panels. Instead, the Tsai–Wu criterion is more appropriate for defining the failure stresses. Full article

The article analyses the impact of wind suction on roof coverings glued with polyurethane adhesives to flat roofs, i.e., roofs with an up to 20% slope. The impact of the cyclical wind was simulated in fatigue tests, gradually increasing the test pressure in repeated sequences until the first delamination occurred. The tests were carried out for eight test sets, with concrete and trapezoidal sheets used as a construction substrate, on whose surface thermal insulation layers were glued with polyurethane adhesive; the thermal insulation layers were EPS (expanded polystyrene) and PIR (polymer mainly of polyisocyanurate groups), respectively, followed by flexible sheets, i.e., a laminated PVC membrane (polyvinylchloride) and an EPDM (terpolymer of ethylene, propylene and a diene with a residual unsaturated portion of diene in the side chain)-type rubber-based membrane. The test results were compared with the functional requirements determined with computational simulation methods for the maximum wind load values on the example of wind loads for Poland. The tests confirmed that some polyurethane adhesives could ensure the operation of flexible sheets used as flat roof coverings that are failure-free from the point of view of resistance to wind suction. Full article

Two series of rigid polyurethane–polyisocyanurate (PU/PIR) foams were obtained. They were modified using powder fillers, such as industrial food cocoa (K5–K15 foam) and instant freeze-dried coffee (KR-KR15) added in amounts of 5, 10 and 15 wt.%. W foam (reference) was obtained without filler. The foams were degraded in a climate chamber for 1 week, 2 weeks or 3 weeks. Appropriate temperature, humidity and UV radiation were set in the chamber, which did not change throughout the degradation process. The foams were also degraded in an oven for two days at 120 °C. The foam tests carried out indicated, among others, on the decrease in compressive strength along with the increase in the residence time of the samples in the chamber. Degraded foams also changed color. Foams containing 5% and 10% of industrial cocoa or freeze-dried coffee were more susceptible to degradation. The addition of 15% coffee or cocoa slows down the degradation process. In the present study, industrial food cocoa and instant freeze-dried coffee were used as modifiers of rigid PU/PIR foam. These fillers have two functions: they accelerate the biodegradation of foams and have antioxidant properties. Full article

This paper focuses on the study of the strength of facade sandwich panels used in building construction. The paper describes the results of experimental and numerical research on the behavior of sandwich panels made of polyisocyanurate core (PIR) and their structural connections when exposed to tensile and compressive loads. In the initial phase of this study, laboratory tests were performed to determine the physical and mechanical characteristics of the material from which the sandwich panels are made. Laboratory tensile and compression tests were performed on small samples of sandwich facade panels. In order to verify the obtained results, they were compared with the numerical analysis performed in the ANSYS software. The numerical model was found to accurately predict the results of the laboratory tests, suggesting that the model can be used to predict the behavior of these panels under different loads in service. The study showed that the foam core sandwich panel exhibits excellent mechanical properties. The results indicate the suitability of foam-based composite structures in the construction industry for various applications, such as roof and wall structures. The findings of this study may help in the development of lightweight and durable construction materials for the industry. Full article