Flexible Polyurethane Foam Research Articles

Flame Retardant Combinations with Expandable Graphite/Phosphorus/CuO/Castor Oil in Flexible Polyurethane Foams

A series of flexible polyurethane foams (FPUFs) were prepared with single and different combinations of flame retardants and additives. Expandable graphite (EG), phosphorous polyol (OP), copper (II) oxide (CuO), and/or castor oil (CAS) were added to FPUF during the foam preparation in a one-step process. The purpose of the study is to evaluate the synergistic effects of the flame retardants, additives, and the presence of bio-based content on the mechanical properties, flame retardancy, and smoke behavior of FPUFs. The combination of 10 wt % EG and 5 wt % OP in FPUF significantly improves the char yield. In the cone calorimeter experiment, the char yield is nearly three times higher than that with 10 wt % EG alone. The smoke behavior is additionally evaluated in a smoke density chamber (SDC). Comparing the samples with a single flame retardant, 10 wt % EG in FPUF considerably reduces the amount of smoke released and the emission of toxic gases. Replacing the amount of 10 wt % polyether polyol in FPUF with CAS maintains the physical and mechanical properties and fire behavior and enhances the bio-based content. The presence of 0.1 wt % CuO in FPUF effectively reduces the emission of hydrogen cyanide. As a result, this study proposes a multicomponent flame retardant strategy for FPUF to enhance the biomass content and address the weaknesses in flame retardancy, smoke, and toxic gas emissions. A starting point is disclosed for future product development.

Development of a simulator for training of fetoscopic myelomeningocele surgery.

To develop a realistic simulation model for laparotomy-assisted fetoscopic spina bifida aperta (SBa) surgery, to be used for training purposes and preoperative planning. The predefined general requirement was a realistic model of an exteriorized uterus, allowing all neurosurgical steps of the intervention. The uterus was modelled using ultrasound and MRI images of a 25 weeks' gravid uterus, consisting of flexible polyurethane foam coated with pigmented silicone. The fetal model, contained an opening on the dorsal side for a customizable spinal insert with all the aspects of a SBa, including a cele, placode, and myofascial and skin layer. The model was assessed in a series of validation experiments. Production costs are low, uterus and fetus are reusable. Placental localization and the level and size of the spinal defect are adjustable, enabling case-specific adaptations. All aspects of the simulator were scored close to realistic or higher for both appearance and functional capacities. This innovative model provides an excellent training opportunity for centers that are starting a fetoscopic SBa repair program. It is the first simulation model with adjustable spinal defect and placental localisation. Further objective validation is required, but the potential for using this model in preoperative planning is promising.

Birth of PU foam technology

Cannon Viking is celebrating the 30th anniversary of its CarDio sustainable liquid CO2 blowing agent technology which produces polyurethane (PU) flexible slabstock foams.

Management of ground tire rubber waste by incorporation into polyurethane-based composite foams

Rapid economic growth implicated the developing multiple industry sectors, including the automotive branch, increasing waste generation since recycling and utilization methods have not been established simultaneously. A very severe threat is the generation of enormous amounts of post-consumer tires considered burdensome waste, e.g., due to the substantial emissions of volatile organic compounds (VOCs). Therefore, it is essential to develop novel, environmentally friendly methods for their utilization, which would hinder their environmental impacts. One of the most promising approaches is shredding, resulting in the generation of ground tire rubber (GTR), which can be introduced into polymeric materials as filler. The presented work is related to the thermomechanical treatment of GTR in a twin-screw extruder with zinc borate, whose incorporation is aimed to enhance shear forces within the extruder barrel. Modified GTR was introduced into flexible polyurethane (PU) foams, and the impact of modification parameters on the cellular structure, static and dynamic mechanical performance, thermal stability, as well as thermal insulation, and acoustic properties was investigated. Emissions of VOCs from applied fillers and prepared composites were monitored and evaluated. Depending on the treatment parameters, beneficial changes in foams’ cellular structure were noted, which enhanced their thermal insulation performance, mechanical strength, and thermal stability. It was proven that the proposed method of GTR thermomechanical treatment assisted by zinc borate particles might benefit the performance of flexible PU foamed composites and hinder VOC emissions, which could broaden the application range of GTR and provide novel ways for its efficient utilization.

Study on the surface properties of the regenerated polyurethane foam micropowder via cryogenic pulverization and its application

The micropowder obtained by cryogenic pulverizing flexible polyurethane foam (FPUF) as a filler is a waste recycling approach which is highly efficient and eco-friendly. Currently, the micropowder has merely been applied roughly and simply in various fields, so it makes sense to study its surface activity in depth to achieve quantitative and efficient reuse. This paper is focused on studying the surface physicochemical properties of the micropowder and its reactivity and compatibility as a filler in polyurethane elastomers. The FPUF was pulverized into a particle of 0–900 μm. The hydroxyl and amine values of the micropowder surface increased from 48.82, 5.99 mg KOH/g to 73.78, 9.12 mg KOH/g, respectively, with the decrease of particle size range from 500-900 μm to 0–100 μm. However, the amount of substance of effective active hydrogens that could react with NCO groups in the polyurethane prepolymer was uncertain due to the viscosity and temperature. Thus, a preliminary attempt was to quantify the effective active hydrogens by FTIR coupled with titration of the NCO content. The mixture with 5% FPUF-1 micropowder had the maximum effective active hydrogens of 3.30 mmol, which could react with NCO groups to form new chemical crosslinking sites. Compared with the pure PU film, microcrosslinking and strong hydrogen bonding are contributors to the good mechanical properties of the composite. Thus, the FPUF micropowder as an organic filler exhibits considerable potential for converting thermoset FPUF into value-added performance materials.

Influence of Flash Graphene on the acoustic, thermal, and mechanical performance of flexible polyurethane foam

In this study, flexible polyurethane foam (PUF) composites were prepared using three types of Flash Graphene (FG) produced from different feedstock material. The acoustic, thermal, and mechanical properties of foam composites containing 0.025 wt% FG were characterized. It was shown that PUF-1 and PUF-3 had higher sound absorption in the frequency range of 500–2000 Hz compared to neat PUF (baseline). PUF-3 experienced a 47% reduction in thermal expansion coefficient relative to the baseline. The tensile strength and compressive modulus of all composites increased by 16–26% and 33–37% respectively. Compression force deflection and tear strength did not change relative to the baseline. This may be explained by the relatively low flake diameter and aspect ratio of each FG which led to agglomeration and impacted load transfer between the filler and matrix. Overall, the addition of 0.025 wt% FG1 and FG3 improved acoustic, thermal, and tensile properties of PUF without diminishing compression force deflection and tear resistance. PUF reinforced with FG had similar or enhanced properties compared to PUF containing commercially available, exfoliated graphene nanoplatelets (GNP). This supports the use of FG as a relatively sustainable, low-cost alternative to exfoliated GNP or chemical vapor deposition (CVD)-grown graphene in porous polymer composites.

Construction of Ti3C2 MXene based fire resistance nanocoating on flexible polyurethane foam for highly efficient photothermal conversion and solar water desalination.

In this work, a bilayer nanocoating was constructed on the surface of flexible polyurethane (FPU) foam with Ti3C2 MXene and polyethyleneimine-modified silica nanoparticles (mSiO2-NP@PEI) through layer-by-layer self-assembly technology, successfully obtaining modified flexible polyurethane composites (MFPU) with excellent flame retardancy, photothermal conversion and solar water desalination properties. The structure and morphology of MFPU foams were characterized by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), Transmission electron microscope (TEM) and Scanning electron microscope (SEM). The MFPU with three coating cycles (MFPU3) had the best flame retardancy and smoke suppression performances, mainly in terms of decreased peak heat release rate (pHRR), peak smoke production rate (pSPR) and total smoke production (TSP) by 71.3%, 62.1% and 74.5%, respectively, compared to those of neat FPU. In addition, MFPU foams exhibited extraordinary light-to-heat conversion and solar water desalination capabilities. MFPU3 could reach 120°C in 138s and its steam conversion efficiency η was as high as 89.6%, which was 116.0% higher than that of unmodified foam and had a 262.8% increase over pure water. The flame retardant MFPU foams with excellent photothermal conversion efficiency will exhibit great application potential in solar water desalination and power generation.

Experimental and Numerical Modeling Study of Toxic Gas Generation During Combustion of Flexible Polyurethane Foam Under a High Humidity Environment

Experimental and Numerical Modeling Study of Toxic Gas Generation During Combustion of Flexible Polyurethane Foam Under a High Humidity Environment

Layer-by-layer assembly of calixarene modified GO and LDH nanostructures on flame retardancy, smoke suppression, and dye adsorption behavior of flexible polyurethane foams

In this study, the effect of LbL coatings based on layered double hydroxide (LDH), graphene oxide (GO), and sodium p-sulfonatocalix[4]arene (SC4A) modified graphene oxide (GOSC4A) on the fire properties and dye adsorption behavior of flexible polyurethane foam was investigated. For this purpose, samples including neat PU foam and modified PU foams with 3, 6, and 9 bilayers of LDH-GO and LDH-GOSC4A coatings were prepared. SEM micrographs of the prepared foams confirmed the presence of LDH-GO and LDH-GOSC4A coatings on the foam surface and showed that the LDH-GOSC4A layers form a denser and more uniform coating on the PUF surface. Combustion studies of prepared foams using CCT and horizontal burning test demonstrated that at the same number of bilayers, foams including LDH-GOSC4A coatings showed better flame retardancy than LDH-GO coated foams. Therefore, the PUF/LDH-GOSC4A 9BL foam showed the best fire properties, and its PHRR, THR, and TSP values ​​were reduced by 28.8, 11.8, and 36.3%, respectively, compared to uncoated PUF. Methylene blue (MB) adsorption studies revealed that adsorption of MB onto PUF/LDH-GOSC4A 9BL is well consistent with the pseudo-second-order kinetic model and its maximum adsorption capacity is 38.46 mg/g based on the Langmuir isotherm equation.

Constructing a bio-based flame retardant coating through co-depositing polydopamine and guanosine 5′-monophosphate disodium salt (GMP) for flexible polyurethane foam

The fire hazard posed by the inherent flammability and smoke toxicity of flexible polyurethane foam (FPUF) often necessitates the incorporation of flame retardants to meet stringent regulations. The development of environmentally friendly strategies to enhance the fire resistance of FPUF is of increasing importance and a significant amount of research has been devoted to this end. In this work, a bio-based coating was constructed by co-depositing polydopamine and guanosine 5′-monophosphate disodium salt (GMP) to increase the fire safety of FPUF. The coating significantly improved the flame retardancy of FPUF. The FPUF@PDA-GMP samples showed an LOI value of 24.5% with a self-extinguishing effect and exhibited reduced release of heat, smoke, CO, CO2, and HCN due to their compact and strong char. The compressive strength at 70% strain of FPUF@PDA-GMP was 8 times higher than that of the control FPUF sample. The coating had a little negative effect on the resilience and improved its elongation at break. This investigation has provided a useful method for designing and producing high-performance foams.

Flexible polyurethane foams reinforced with graphene and boron nitride nanofillers

AbstractThe effect of three types of nanofillers on the physical, mechanical, and thermal properties of flexible polyurethane foams (FPUF) was studied. FPUF with nanofillers are of interest to the automotive industry due to their potential for enhancing compression properties and enabling sustainable foams. Holey and wrinkled flash graphene, and untreated and silane coated boron nitride were tested as fillers up to 0.1 wt% loading level. Flash graphene filled FPUF showed significant improvement in compressive properties, especially at the 0.025 wt% loading level, showing a 22% increase in compressive force deflection at 25% strain and a 17% increase at 50% strain compared to the unfilled control foam sample. Boron nitride nanoparticles, treated and untreated, were shown to be an effective means of reducing wet compression set properties, addressing a key area of concern for sustainable polyols. Wet compression set was reduced by 20%–30% for most boron nitride foams compared to their unfilled control samples. Boron nitride may enable implementation of more sustainable polyols in automotive FPUF. Nanofillers did not significantly improve thermal stability of FPUF.

Halloysite-Decorated Mechanically Robust Polyurethane Nanocomposite Foams for Acoustic Relevance

Noise pollution affects human health and the environment. In this study, halloysite nanoclay (HNC) was employed as a bio-nanofiller with different ratios (1–5 wt %) to improve the thermal, mechanical, and sound absorption capabilities of the flexible polyurethane (FPU) foam. FPU/HNC composites were characterized using X-ray diffraction, Fourier transform infrared, and field emission scanning electron microscopy techniques. In addition, porosity, apparent density, and sol fraction for FPU/HNC composites were investigated. Compared with the unfilled FPU foam, the results of the FPU/HNC 1% sample showed that the density achieved a maximum value of 38.17 Kg/m3, while the porosity was reduced to 83.48%. Moreover, the sol fraction reached the highest value of 13.4% for the FPU/HNC 5% sample. Furthermore, thermogravimetric analysis revealed that adding 1 wt % HNC improved thermal stability than the unfilled FPU. Nevertheless, the DSC measurement proved that HNC increased the glass transition temperature (Tg) for the composites’ soft segments. Intriguingly, the mechanical measurements exposed that the compressive and tensile strength of the FPU/HNC 1% sample was enhanced to 158.93 and 154.45%; at the same time, the elongation at break dropped to 124.04%. Nevertheless, the sound absorption measurements (20 mm thickness) showed a slight shift to the mid-frequency range (315–1600 Hz) for FPU/HNC composites than the unfilled FPU.

Mechano-chemical rubber reclamation using aminolysis products of waste flexible polyurethane foams as the devulcanizing agent

Rubber and polyurethane are polymers that are widely used but difficult to decompose in the natural environment. In this work, polyurethane aminolysis products (PAPs) are used to assist in the devulcanization of waste rubbers for the first time. The amine groups contained in PAPs can couple with the radicals generated by the scissions of crosslink bonds under the action of mechanical shear force, enhance the degree of devulcanization, and thus improve the mechanical properties of the reclaimed rubbers (RRs). The addition of PAPs can also shorten the optimum cure time of the RRs and improve the crosslink density and hardness of the RR re-vulcanizates. Using 1.8 phr of lower-layer PAPs prepared at 120 °C, the RR re-vulcanizate exhibit a tensile strength of 16.48 MPa, an elongation at break of 330.2%, and a tear strength of 48.5 MPa. This method realizes the dual high-value recycling of waste polyurethanes and rubbers, exhibiting bright application prospects.

Polyurethane Foam Waste Upcycling into an Efficient and Low Pollutant Gasification Syngas.

Waste treatment has attracted much attention and, in this regard, gasification processes offer an efficient thermochemical technique that can produce a syngas rich in hydrogen. This technique has been well developed for solid waste and biomass while investigations on gasification of polymeric foam are rare. Therefore, this study explores the treatment of polyurethane foam waste with different gasifying agents, based on thermodynamic modeling. The polymeric foam gasification was developed using the best model for estimating higher heating value (gross calorific value). As the results indicated, models based on both ultimate and proximate analyses had better performance in predicting higher heating value. As one of the main objectives and novelties, the steam and air gasification performance of flexible and rigid polyurethane foam wastes was investigated and compared from efficiency and CO2 emission viewpoints. Polyurethane foam gasification by steam resulted in higher hydrogen efficiency, led to lower energy efficiency and produced lower CO2 emissions compared to gasification by air. A hydrogen efficiency of 41.4% was obtained for gasification of waste flexible polyurethane foam by steam. An energy efficiency of 76.6% and CO2 emission of 7.43 g per mole of feedstock were attained for waste flexible polyurethane foam gasified by air.

Flexible Polyurethane Foams Reinforced by Functionalized Polyhedral Oligomeric Silsesquioxanes: Structural Characteristics and Evaluation of Thermal/Flammability Properties.

In this work, we report on flexible toluene diisocyanate (TDI)-based polyurethane foams (FPUFs) chemically modified by POSS moieties, i.e., octa (3-hydroxy-3-methylbutyldimethylsiloxy) POSS (OCTA-POSS) and 1,2-propanediolizo-butyl POSS (PHI-POSS). The influence of silsesquioxane on the PU foaming process, structure, morphology, physicochemical, and mechanical properties, as well as flammability, was examined. FT-IR analysis provided evidence for the chemical incorporation of the nanofiller into the foam structure. It was found that the addition of POSS increases the apparent density of the foam and its compressive strength. The XRD and SEM-EDS techniques showed the uniform distribution of POSS in the FPUF with agglomeration depending on the kind and content of the introduced POSS moieties. The analysis of the thermogravimetric and microcalorimetry data revealed an improved resistance to the burning of FPUFs containing reactive POSS, as evidenced by the reduced rate of heat release (HRR). Importantly, the mechanical properties tests showed that the incorporation of silsesquioxane nanoparticles into the polyurethane structure via covalent bonds strengthens the foam integrity.

A biomimetic structured bio-based flame retardant coating on flexible polyurethane foam with low smoke release and antibacterial ability

Flexible polyurethane foam (FPUF) is widely used in our life, but it is inherent flammable. The demand for environmental-friendly multi-functional FPUF has been increasing rapidly in the last decade. In this work, a novel bio-based flame retardant coating was constructed by chemically reacting sodium alginate (OSA) and polydopamine (PDA) on the FPUF, followed by depositing nanorod-like β-FeOOH molecules through complexation reaction to form a biomimetic structure. The limiting oxygen index of the coated FPUF samples reached 25.5%. The peak heat release rate was reduced by 45.0%, and the smoke density of the coated sample was decreased by 69.1% compared to that of the control FPUF sample. It was proposed that the OSA-PDA-β-FeOOH decomposed during combustion to promote the formation of compact crosslinked char and released inert gases to dilute the combustible gases, and the β-FeOOH transferred to Fe2O3 to settled the smoke particles reducing the smoke release. Furthermore, the coating with shark skin like structure endowed FPUF antibacterial ability because of its good superoleophobicity underwater. This work provided a novel strategy to construct a biomimetic multifunctional coating on the FPUF.

Preparation of Polyols and Polyurethane Foams from Olein By-Product of Tanning Industry

Olein produced from the solid residues of the tanning industry is already employed as raw material to obtain greasing oil for leather. However, new applications for this product may be advantageous regarding environmental impact and sustainability of this industry. In this work, flexible polyurethane foams (FPUFs) were prepared from polyols obtained from olein. A polyol from olein was prepared through alkaline glycerolysis. The glycerolysis conditions of temperature, glycerol/olein molar ratio, amount of catalyst and reaction time were optimized using a 24 factorial design, resulting in an olein polyol containing around 75% of monoacylglycerols, hydroxyl value (388.68±0.40 mg KOH.g-1), and hydroxyl functionality of 2.89. FPUFs were prepared at NCO/OH ratios of 1.2:1 and 1.3:1, using an aliphatic hexamethylene diisocyanate trimer and water as foaming agent. The foams were characterized through FTIR, thermogravimetry, morphology, extractable materials, and mechanical properties. Characteristics urethane/urea groups formation were verified by FTIR as well as typical mass loss steps in the thermal decomposition curves. The foams morphology showed a structure composed mainly for polygon-type closed-cells. The obtained FPUFs presented a content of extractable materials lower than 3%. The mechanical properties of the foams were dependent on the NCO/OH ratio, and the foam prepared at the ratio of 1.2:1 stood out as a potential material to be used in the production of mattresses. This study demonstrated the feasibility of transforming olein, a solid residue of the tanning industry, as a precursor to prepare PU foams, which may be a promising material for mattress applications, considering the observed features.

Inorganic-organic hybrid coatings from tea polyphenols and laponite to improve the fire safety of flexible polyurethane foams

Inorganic-organic hybrid coatings prepared via an impregnation assembly of eco-friendly materials exhibited dramatically flame-retardant properties on flexible polyurethane foam (FPUF). A nickel-complex of tea polyphenols (TP-Ni) was synthesized, and TP-Ni and laponite (LAP) were coated on the surface of FPUF. LAP/TP-Ni can be homogeneously dispersed on the surface of FPUF. Moreover, the melt-dripping phenomenon of 1LAP/4TP-Ni/FPUF was completely inhibited during the vertical flame test (UL-94) with 41.2 wt% weight gain, and it showed self-extinguished behaviors at once and passed the UL-94 V-0 rating. Additionally, the values of peak heat release rate and peak smoke production rate of 1LAP/4TP-Ni/FPUF were reduced by 71.6% and 60.9%, compared with the control. The content of gaseous toxic substances, such as CO and NCO-containing compounds, was also decreased, indicating the effect of TP-Ni/LAP on the toxicity suppression of flame-retardant FPUF. Encouragingly, the coatings deteriorated the tensile property of FPUF inconspicuously. Interestingly, the coatings do not contain traditional flame retardant elements, which offers an innovative approach for designing flame retardants. Thus, these inorganic-organic hybrid coatings show the promising potential to decrease the fire risk of FPUF.

Preparation of flexible biobased non-isocyanate polyurethane (NIPU) foams using the transurethanization approach

A new process for the preparation of non-isocyanate polyurethane (NIPU) flexible foams has been implemented. Biobased amino-telechelic NIPU oligomers were prepared by an organo-catalyzed transurethane polycondensation reaction of fatty biscarbamates with fatty diols and diamines. The obtained oligomers were reacted with a biobased multi-epoxide molecule as crosslinking agent, in the presence of a poly(hydromethylsiloxane) or its copolymer as foaming agent and surfactant. The crosslinking and foaming reactions were monitored by rheometric, volumetric and FTIR studies. The foams can be obtained in <30 min at 100 °C or in 14.5 h at room temperature. The prepared foams displayed cell diameters in the range of 210 to 430 μm associated with densities in the range of 130 to 400 kg/m3. They also exhibited thermal stabilities above 300 °C, as well as a soft character attested by negative Tg values ranging from −10 to −28 °C, and low values of the Young modulus varying from 1.0 × 104 Pa to 6.3 × 104 Pa. The recovery time, hysteresis loss and the firmness of these foams were found to be dependent on their chemical structures.

Addition Of Chain Extender To Improve Flexible Polyurethane Foam Characteristics Of Palm Oil Polyol

The use of 100% palm oil polyol without the addition of a chain extender produced foam which initially expands and then collapses so that the resulting foam has tight pores, dense texture, and brittle (brittle). It was necessary to use a chain extender to improve the flexible properties of the foam. This study aimed to examine the ratio of palm oil polyols with a chain extender to produce flexible polyurethane foam with good characteristics. The treatment of this study was a combination of types and comparisons of palm oil polyols with chain extenders which were carried out 3 times, consisting of factor A = type of chain extender (diethylene glycol (DEG), diethanolamine (DEA), and polyethylene glycol (PEG)-400) and factor B = ratio of palm oil polyols. with a chain extender (80%:20%; 70%:30%; 60%:40%; 50%:50%). The obtained foam was observed visually, foam development, and foam density. The best sample for each type of extender was analyzed by FTIR. The results showed that 40% PEG-400 has succeeded in producing flexible polyurethane foam with higher expansion (291.22%), lower density (29 kg/m3), and visually has the best flexible properties. Based on FTIR analysis, the use of PEG-400 in the polyol system can increase the reactivity of palm oil polyols to isocyanates.