Fully renewable materials will be a key component of sustainable plastic development and management, and the industrial reliance on petroleum-derived monomers, including aromatic diisocyanates used in polyurethanes (PUs), must be minimized to meet sustainability and production goals. To date, aliphatic diisocyanates have shown great promise as renewable monomers, and scalable production is imminent. This work demonstrates a systematic study and application of aliphatic diisocyanates for the preparation of rigid PU foams. Aliphatic 1,6-hexamethylene diisocyanate (6-HDI) was incorporated with multifunctional renewable polyols and cross-linkers to produce rigid polyurethane-polyisocyanurate foams with high renewable carbon content. Morphological, thermal, and mechanical analyses of these novel foams indicated similar properties and performance to those of commercial rigid foams. The described synthesis of rigid foams without utilization of aromatic diisocyanates broadens the scope of rigid foam formulations possible and serves to advance the understanding of renewable foam and material development.

Experimental and numerical study of novel metal damping ceramsite concrete wall panels

Synthesis and Characterization of Cerium Oxide/Polyurethane Rigid Foam Composites

The need to reduce polyurethane (PU) foam waste has encouraged the development of sustainable foam formulations based on recycled raw materials and environmentally friendly additives, addressing both waste management and comparable foam properties to those based on fossil resources. In the present investigation, more sustainable water-blown rigid PU foams were investigated using recycled polyol and halogen-free flame retardants (FRs) for fire-resistant insulation applications. Two series of foam formulations were prepared: a first series with virgin polyol and the inclusion of a halogen-free FR additive (6 wt%) and a second series with recycled polyol (10% added respect to the total polyol) and halogen-free FR additives (6 wt%). Two types of FR were used: FR900, specifically identified as 3,9-Dimethyl-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane-3,9-dioxide, in powder form with 24% phosphorus content and reactive polyol based FR140, an oligomeric ethyl ethylene phosphate, in liquid form with 19% phosphorus content. The density, cellular structure, aged thermal conductivity, dimensional and hydrolytic stability, fire properties, and mechanical properties were characterized for novel foamed systems. Rigid foamed materials with very low densities around 50 kg/m3 were obtained. On the one hand, the inclusion of FR900 into the PU formulation containing virgin polyol generated foam with the lowest thermal conductivity (36.10 mW/mK) due to the smaller open cell content (11.7%) and cell size reduction (433 microns). On the other hand, the inclusion of recycled polyol reduced the foam density by 6 kg/m3 (44.1 kg/m3), increased the cell size average (848 microns) and open cell content (15.1%), maintained thermal conductivity (38.73 mW/mK), slightly improved the fire properties, and worsened the mechanical properties in comparison with the PU reference containing only virgin polyol. The results obtained by the foam containing recycled polyol and 6% FR900 are remarkable, presenting an increase in density (50.3 kg/m3) and in open cell content (73%), but a very high reduction in cell size (465 microns) and thus a low value of thermal conductivity of 37.04 mW/mK with respect to the reference material containing recycled polyol. Moreover, this PU foam containing recycled polyol and FR900 offered improved fire resistance (148.2 kW/m2 of Maximum Average Rate of Heat Emission (MARHE), 179.1 kW/m2 of Maximum Heat Release Rate (HRRmax), and 24.6 MJ/m2 of Total Heat Release (THR)) and mechanical properties (6.97 MPa of Young's modulus and 0.24 MPa of collapsed stress) for the construction sector. The inclusion of FR140 does not improve the properties of the foam system containing recycled polyol, mainly due to the deterioration of the cellular structure (in the open cell content and cell size).

Rigid polyurethane foams are often manufactured in sealed molds, so knowledge of the density distribution in the molded blocks is essential. A study was conducted with the aim to estimate density distribution within a rigid polyurethane foam block (average core density of ≈96 kg/m3) manufactured in a rectangular sealed mold. The density of 150 rectangular samples was determined experimentally. Characteristic locations of the foams' columns in the block were outlined, having similar foaming conditions. Averaged density in the characteristic columns was calculated for each characteristic location. A mathematical model was developed based on density data of characteristic columns, approximated with second- and third-degree polynomials. Density distribution was calculated, and corresponding color charts with density zones and equidensity lines were constructed for six horizontal and two vertical sections of the block. It was found that the common center of the elliptical equidensity lines is located asymmetrically, ≈17 mm above the geometric center of the untrimmed block. Density gradients were calculated in directions parallel and perpendicular to the foams' rise direction. The developed mathematical model allowed us to estimate density distribution within the rigid polyurethane foam block manufactured in a rectangular sealed mold.

Polymer-based insulation materials are widely used to enhance the energy efficiency of buildings; however, their growing application raises concerns related to resource use and end-of-life management. Rigid polyurethane (PUR) foams are key core materials in structural insulated panels due to their favorable thermal and mechanical performance, yet their life cycle environmental impacts-particularly at end-of-life-remain insufficiently quantified. In this study, a cradle-to-grave life cycle assessment (LCA) of PUR-based insulation used in structural insulated panel systems is conducted in accordance with ISO 14040/44 and EN 15804 standards. The assessment is performed using Sphera LCA software (version: GaBi 10.5) and the CML 2016 impact assessment method. Formulation-level variations in rigid PUR foams, including changes in methylene diphenyl diisocyanate content and pentane blowing agent ratio, are explicitly incorporated to evaluate their influence on key environmental impact categories. The results indicate that increasing pentane content leads to higher global warming potential, while this effect may be mitigated or intensified by concurrent changes in diisocyanate content and foam density in fully formulated systems. Three end-of-life scenarios-landfilling, incineration with energy recovery, and mechanical recycling-are analyzed. The findings provide material-level, decision-relevant insights that support environmentally informed formulation strategies and contribute to the development of more circular polymer-based insulation solutions for the built environment.

Lightweight and high-performance polyimide rigid foams (PIRFs), exhibiting outstanding heat resistance and mechanical properties, as well as excellent flame retardancy, are increasingly required for specialized load-bearing applications. However, commercially available polyimide (PI) foams, which are mostly flexible and low-density, are thermally and mechanically inadequate for high load-bearing purposes. Herein, a scalable and high-efficiency “kill two birds with one stone” cocross-linking and foaming strategy is developed for the fabrication of highly heat-resistant, mechanically strong, and flame-retardant cocross-linked polyimide rigid foams (PIRFs) using the norbornene-end-capped cross-linkable blowing agent (NE-CBA) as both cross-linking agent and blowing agent. Benefiting from the simultaneous construction of high-density cocrosslinked networks and tailorable closed-cell structures via the reaction of maleic anhydride-end-capped PI oligomer (ME-PIO) and NE-CBA, the resultant cocrosslinked PIRFs exhibit exceptional heat resistance, with an ultrahigh glass transition temperature (Tg) of 410.6 °C and a remarkable thermal degradation temperature (Td) of 500.3 °C. Moreover, they possess outstanding mechanical properties, with a high compressive strength of 1.9 MPa at room temperature and 1.7 MPa at as high as 200 °C, with a low mass density of 157 kg/m3. In addition, the PIRFs exhibit excellent thermal insulation properties, with low thermal conductivities (λ) of 0.041 W/(m·K) at room temperature and 0.057 W/(m·K) even at 200 °C, as well as desirable flame retardancy with a high limiting oxygen index (LOI) exceeding 40%. Owing to the dual functionality of the NE-CBA employed in this strategy and the resulting synergistic effect, the PIRFs achieve the Tg > 410 °C and compressive strength exceeding 1.9 MPa at a foam density of 157 kg/m3. This represents the successful simultaneous achievement of low density, ultrahigh heat resistance, and high mechanical strength. The highly heat-resistant and mechanically strong cocross-linked PIRFs, with superior thermal insulation and flame-retardant performance, show significant potential in fields such as aerospace engineering, shipbuilding, railway transportation, and other specialized high-temperature applications.

This study examines the dimensional stability (DS) of polyisocyanurate rigid (PIR) foams under high relative humidity (RH = 90%) and elevated temperature (T = 70 °C), representative of the extreme conditions that may be encountered in roofing applications. Lateral expansion is observed in the plane perpendicular to the rise direction, which is strongly depth-dependent (Z-axis) and decreases from 5.3% for the surface layer (0–5 mm) to around 1.2% for the inner layers (Z ≥ 15 mm). This phenomenon is mainly attributed to the lower isocyanurate content near the surface and is amplified by the higher partial pressure of isopentane (+9%) near the surface. In contrast, contraction occurs in the rise direction (also called the thickness direction or TD) and remains nearly constant at −1% for Z ≥ 15 mm. This anisotropic behavior is attributed to the elongated cell morphology in the TD, inevitably leading to a decrease in mechanical strength in the plane perpendicular to the rise direction. Moisture content, quantified using Karl Fischer titration, is estimated at around 2.2 wt % (under humid conditions) and appears to play a dual effect, both plasticizing the polymer matrix and increasing internal gas pressure. Postcuring at T = 140 °C significantly increased cross-linking and improved DS, reducing foam expansion in the machine direction (MD) and cross-machine direction (CMD) from ΔL/L0 ≈ 5% to about 2% for the surface layer (0–5 mm). All these findings point toward the dominant role of moisture level, isocyanurate content, and cell shape factor of the final products on the long-term dimensional stability of PIR foams in humid, thermally stressed environments.

Purpose The polyurethane sector primarily relies on petrochemical substances, including polyols and isocyanates. Given the swift consumption of fossil fuel resources and the rising concerns about ecological issues and global warming, this study aims to explore the sustainable advancement of polyurethane rigid foam by using renewable biopolyols derived from agricultural waste liquefaction. Design/methodology/approach The liquefaction of lignocellulosic biomass involves breaking down complex polymers into smaller molecules using heat, chemicals and catalysts to prepare biopolyol as a renewable feedstock for the polyurethane industry. Spectral analysis of the liquefaction products verified that the process achieved the desired outcome and indicated the presence of hydroxyl groups. The biopolyol analysis demonstrated a biomass conversion rate of up to 87% and a hydroxyl number between 230 and 250 mg KOH/g, suggesting that this biopolyol could serve as a viable alternative to petrochemical polyols. Findings Various formulations of biopolyol obtained from rice straw liquefaction, conducted at 160 °C for 2 h, were prepared. Intensive study was conducted on the applicability of using biopolyol in rigid foam refrigerator formulation in comparison to petroleum counterparts. The results obtained from scanning electron microscopy showed that the biopolyol-based foams had a symmetrical cell structure and a significant proportion of sealed cells. Biobased foam demonstrated superior thermal insulation compared to its petrochemical-based equivalent. Originality/value These results underscore the feasibility of agricultural waste liquefaction as an eco-friendly approach for synthesizing biopolyols and their application in polyurethane foam production. The study contributes to the development of sustainable materials in the polymer industry and supports the transition toward renewable feedstocks in rigid foam applications. The study, moreover, introduces PEG 400 as a novel liquefaction solvent, offering improved compatibility with rigid polyurethane systems and establishing a new benchmark for sustainable rigid foam production.

With rising concerns over the toxicity and environmental impact of isocyanates, it is high time to explore viable isocyanate-free alternatives for polymer foams. While polyurethane foams have long dominated the market due to decades of refinement, achieving comparable properties with alternative chemistries remains a challenge. The aza-Michael addition reaction, which proceeds under mild conditions, offers a promising route to synthesize crosslinked polymer foams without isocyanates. In this study, we demonstrate the preparation of rigid polymer foams via aza-Michael addition between multifunctional monomers using physical blowing agents. A key innovation lies in introducing an intermediate pre-reaction step, where varying the reactant stoichiometry allowed us to finely control the final polymerization kinetics and exothermicity. This tunability enabled modulation of foam rise, density and morphology, without altering the base formulation. The resulting foams were partially open-cell with densities as low as ~71 kg·m −3 , average cell radius of ~500 μm, and thermal conductivity of ~48 mW·m −1 ·K −1 . The foams were mechanically robust, with excellent recovery after 80% compression. With further optimization of the foaming process and the use of tailored surfactants and blowing agents, aza-Michael-based foams could emerge as strong candidates to replace rigid polyurethane foams in commercial applications. • Rigid foams via aza-Michael chemistry as an isocyanate-free alternative route. • Used tunable pre-reaction to control polymerization kinetics and exothermicity. • Pre-reaction stoichiometry modulated foam rise and properties at fixed formulation. • Obtained low density foams with low thermal conductivity and high shape recovery.

Minimized aging of isocyanurate-based rigid cellular foams for buildings through tailored barrier facers and optimized formulation

Development of polyurethane rigid foam – phase change material composites with latent heat storage capacity for thermal insulation: Insights from the ECHO project

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.

Gambier is one of the largest sources of condensed tannins in Indonesia which has the potential as a raw material for rigid foam. Environment friendly rigid foam can be made from a mixture of gambier tannin, albumin, pTSA and hexamine. The purpose of this study was to investigate how albumin preparation and gambier tannin extraction methods affect the quality of rigid foam. Albumin preparation was carried out by a fermentation process using Rhizopus sp. yeast and then drying using the pan drying and foam drying methods. Extraction was carried out by heating using a magnetic stirrer and microwave-assisted methods. Based on the results of the study, the best rigid foam is the rigid foam with a combination of pan drying and microwave assisted. This rigid foam has a high density, high compressive strength, low swelling degree, resulting in a denser and harder rigid foam and based on SEM test showed closed and open pores in the rigid foam with a pore size of around 60.47 µm. Keywords: Secondary metabolites, hydrolyzed tannins, Maillard reaction, tannins extract.

Polyurethane (PU) is widely recognized for its efficient oil sorption properties. However, this capacity is highly dependent on its intrinsic chemical composition and morphological structure, which can be altered by mechanical or chemical treatments commonly applied before using it as a sorbent. In this study, we present a comprehensive investigation of the oil sorption behavior of both soft and rigid PU foams, and their blade-milled ground (BMG) counterparts obtained by mechanical treatment of several recycled PU-based products, including seats, mattresses, side panels of cars, packaging components, and insulating panels of refrigerators and freezers. We found that blade milling the soft PU foams leads to a significant reduction in oil sorption capacity proportional to the extent of grinding. Pristine soft PU foams and BMG-PUs with intermediate particle size (−250 μm–1 mm) exhibited the highest oil uptake (20–30 g/g), whereas the finest fraction (5 μm–250 μm) showed a lower capacity (3–7 g/g). In contrast, rigid PU foams showed consistently low oil sorption (~5 g/g), with negligible differences between the original and ground materials. At the macroscopic level, optical and morphological analyses revealed the collapse of the 3D porous network and a reduction in surface area. On the microscopic scale, spectroscopic, structural, and thermal analyses confirmed phase separation and rearrangement of hard and soft segmented domains within the polymer matrix, suggesting a different mechanism for oil sorption in BMG-PU. Despite reduced performance compared to pristine foams, BMG-PU powders, especially those with intermediate dimensions and originating from soft PU foams, present a viable, low-cost, and sustainable alternative for oil sorption applications, including oil spill remediation, while offering an effective strategy for effective recycling of PU foam wastes.

In the current ‘Anthropocene’ era, where global warming and ecological shifts pose a threat to human existence, ecological accountability within the arts has become indispensable. In the realm of modern Tamil theatre scenography, there has been a recent surge in the use of non-biodegradable materials such as Polystyrene (Rigid Foam), plastics, and chemical paints, fostering a ‘disposable culture’. This trend is detrimental both ecologically and economically. This study explores the feasibility of implementing Australian designer Tanja Beer’s theory of ‘Ecoscenography’ within the context of Tamil theatre. The theory advocates for transforming stage design from a mere decorative artifact into an ecological event integrated with the environment. Employing a qualitative research methodology, this study analyzes Tanja Beer’s three theoretical stages—’Co-creation’, ‘Celebration’, and ‘Circulation’—through a comparative analysis with traditional Tamil theatre forms, such as Koothu, and contemporary theatrical endeavors. The study concludes that while this theory originates from the West, it shares intrinsic values with the traditional material culture of Tamil theatre. Furthermore, it establishes that the utilization of local, sustainable resources offers a viable solution to significantly reduce production costs while ensuring environmental sustainability.

Polyurethane (PU) foam is used almost everywhere—from packaging to insulation and construction—but its production still relies largely on petroleum-based ingredients. In this study, we explored castor oil as a renewable alternative to conventional polyols, aiming to create PU foams that are both sustainable and versatile. We prepared the foams by reacting castor-oil-based polyol with methylene diphenyl diisocyanate (MDI), using different amounts of water as a blowing agent (1%, 10%, and 20% w/w) and silicone surfactant (2%, 10%, and 18% w/w) to help stabilize the foam structure. By adjusting these components, we examined how the formulations affected the foam’s appearance, density, and strength. Small changes in water and surfactant content led to three clear foam types: a rigid foam (1% water, 18% surfactant), a semi-rigid foam (10% water, 2% surfactant), and a flexible foam (20% water, 10% surfactant). The rigid foam showed the highest strength and density, while the semi-rigid and flexible versions had progressively softer and lighter structures. Overall, our findings show that castor-oil-based PU foam can be tuned to meet different performance needs simply by adjusting its formulation. This offers a practical and renewable pathway for producing PU foams with properties comparable to those made from petroleum-based materials.

This study explores the potential of pine bark—a highly accessible and underexploited by-product of forestry and food processing—as a renewable raw material for rigid polyurethane (PUR) foam production. Under optimal extraction conditions, water-soluble extractives rich in carbohydrates were isolated from biomass with a yield of 25% and subsequently condensed with propylene carbonate (PC) to produce bio-based polyols. The polyols synthesized at a PC/OH molar ratio ranging from 1 to 5 were incorporated into rigid PUR foam formulations as substitutes for commercial polyether polyols. The foams containing bio-polyols synthesized at a PC/OH ratio of 3 demonstrated the highest compressive strength and thermal insulation performance, exceeding those of the reference material by 30% and 9%, respectively, and exhibited enhanced thermo-oxidative stability. Incorporation of extracted bark up to 10 wt% as a filler in the PUR matrix led to a decrease in mechanical properties to the level of the reference foam and a 19% reduction in thermal insulation capacity, without affecting the closed-cell content. Cone calorimetry revealed that both filled and unfilled bio-polyol-based PUR foams exhibited lower degradation rate, heat release rate, and total smoke release compared with the reference material, indicating reduced flammability and a lower tendency toward fire propagation.

This research aims to develop polyurethane foam using recycled PET (Polyethylene Terephthalate) and HDPE (High-Density Polyethylene) plastic bottles as substitutes for polyol. Waste PET bottles were recycled through a glycolysis process to produce BHET (bis(hydroxyethyl) terephthalate), utilized as a polyol substitute in polyurethane foam production. The foam was synthesized by reacting polyol with Methylene Diphenyl Diisocyanate (MDI), with variations in the composition of distilled water as a blowing agent, silicone as a surfactant, and steel slag (10%, 10%, 10%, and 60%) to enhance mechanical properties. Four polyurethane foam samples were tested, resulting in rigid, flexible, and semi-rigid foams, depending on the formulation. Sample 1 demonstrated a compressive strength of 0.225 MPa, Young's modulus of 0.0139 MPa, yield strength of 0.174 MPa, and density of 0.11 g/cm³. Sample 2 exhibited a compressive strength of 0.18 MPa, Young's modulus of 0.0109 MPa, yield strength of 0.117 MPa, and density of 0.06 g/cm³. Sample 3 had the lowest compressive strength (0.02 MPa), Young's modulus (0.00079 MPa), yield strength (0.0092 MPa), and density (0.09 g/cm³). Sample 4 recorded a compressive strength of 0.12 MPa, Young's modulus of 0.0116 MPa, yield strength of 0.0901 MPa, and density of 0.04 g/cm³. Sample 1 exhibited the highest mechanical performance, while Sample 3 showed the lowest. These results indicate that polyurethane foam with optimal compressive strength, Young's modulus, yield strength, density, and flexibility can be produced, meeting the requirements of SNI (Standar Nasional Indonesia) Standard 0111-2009 for shoe applications.

Poly (urethane-urea) foam (PUU Foam) from an amine-based polyether polyol (APP) is different from Sucrose-Sorbitol based polyether polyol (SSPP). In this study, rigid PUU Foams produced from an amine-based polyol, (Amine value: 100 mg KOH/g, Hydroxyl value of 408 mg KOH/g) was compared with Sucrose-Sorbitol based polyether polyol, (Hydroxyl value:380-420 mg KOH/g, Amine value: 0 mg KOH/g) using varying isocyanate ratio (Isocyanate index). Effect of varying Isocyanate index on foaming parameters, physical, chemical, morphological as well as thermomechanical properties were evaluated in both kinds of foams. A higher NCO index resulted in increased crosslinking, which improved the compressive strength of PUU foams through the formation of isocyanurates, thus enhancing their thermal stability. Fourier-transform infrared (FTIR) spectroscopy was utilized to analyze the chemical properties of the foams. Cell size through scanning electron microscopy (SEM) and closed cell content and dimensional stability of the foams were also carried out to assess the morphological structures of the foams. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were performed to examine the thermal properties of the foam. The thermal conductivity of the foams, prepared with various isocyanate indexes, ranges from 25 to 45 mW/m K, especially for APP based foams with NCO index of 175 resulted in low thermal conductivity of 25 mW/m K (at RT) and 14 mW/m K (at LN2), indicating their potential suitability for cryogenic insulation.