Synergistic effect of melamine and tricresyl phosphate on fire retardant properties of semi flexible polyurethane foam

Green flame-retardant flexible polyurethane foam based on cyclodextrin

For comfortable driving conditions, flexible polyurethane (PU) foams are used for sound absorbers in noise, vibration, harshness (NVH) systems. The cellular structures of PU foams are important to improve the sound absorption efficiency, and the cell morphology is strongly dependent the use of experimental ingredients such as catalysts and cross-linking agents. Uniform cavity size distribution is achieved by controlling the catalyst ratio between gelling and blowing catalysts, and the optimum catalyst ratio (9:1) is used with a diethanolamine (DEA) cross-linker for improved sound absorption efficiency. DEA affects pore morphology by preventing phase separation in PU matrix, and the number of open pores reduces with increasing DEA contents. Sound absorption coefficient shows the highest at 9:1 catalyst ratio and 0.9 g DEA usage in the flexible PU foams under disturbed phase separation conditions.

Noise pollution is the primary environmental issue that is increasingly deteriorated with the progress of modern industry and transportation; hence, the purpose of this study is to create flexible PU foam with mechanical properties and sound absorption. In this study, hollow ceramic microsphere (HCM) is used as the filler of polyurethane (PU) foam for mechanical reinforcement. The sound absorption efficacy of PU pores and the hollow attribute of HCM contribute to a synergistic sound absorption effect. HCM-filled PU foam is evaluated in terms of surface characteristic, mechanical properties, and sound absorption as related to the HCM content, determining the optimal functional flexible PU foam. The test results indicate that the presence of HCM strengthens the stability of the cell structure significantly. In addition, the synergistic effect can be proven by a 2.24 times greater mechanical strength and better sound absorption. Specifically, with more HCM, the flexible PU foam exhibits significantly improved sound absorption in high frequencies, suggesting that this study successfully generates functional PU foam with high mechanical properties and high sound absorption.

Flexible polyurethane (PU) foams with different loading mass fraction (0%–2.0%) of fumed silica were synthesized by free-rising foaming method. The addition of 1.4% fumed silica makes the cells diffuse more uniform in the PU foam and the temperature of degradation occurring with a maximum weight loss rate is about 7 °C higher than that of pure PU foam. Most significantly, the sound absorption peaks of the filled PU foams shift to the low frequency region (from 997 Hz to 711 Hz) with increasing fumed silica content (0%–2.0%). The average sound absorption coefficients of filled PU foams increase except the content of 0.35% fumed silica. The experimental results show that flexible PU foams filled with fumed silica have excellent sound absorption characteristics in low-frequency regions.

This study proposes a combination for reciprocal reinforcement between warp knitting spacer fabrics and PU foams. PET/Kevlar nonwoven fabrics are made with an 80:20 ratio and an incorporation of various needle-punching speed of 100, 150, 200, 250, and 300 needles/min. Ascribing to having an optimal bursting strength, sound absorption coefficient, and limited oxygen index (LOI), the PET/Kevlar nonwoven fabric that is made by 200 needles/min are selected to be combined with a glass-fiber fabric by applying needle punch in order to form a surface layer. Next, warp knitting spacer fabrics and the nonwoven fabrics are laminated, followed by being combined with polyurethane (PU) foam that are featured with different densities of 200, 210, 220, 230, and 240 kg/m3 in order to form spacer fabric/PU foam composites with multiple functions. The composites are then tested with a drop-weight test, a compression test, a bursting strength test, a sound absorption test, and a horizontal burning test. The test results indicate that all spacer fabric/PU foam composites reach a horizontal burning level of HF1, and their sound absorption coefficients at 2500-4000 Hz also suggest a satisfactory sound absorption. In particular, the optimal residual stress and compressive strength are present when the composites contain 210 kg/m3 PU foam. Similarly, the optimal bursting strength of the composites occurs when they are composed of 230 kg/m3 PU foam. The spacer fabric/PU foam composites are proven to have high strengths, sound absorption, and fire retardant, and thus have promising potentials for use as construction materials and light weight composite planks.

Rigid polyisocyanurate-modified polyurethane (PIR) foams remain the insulation materials of choice for many commercial and residential construction applications. PIR foam boards, produced by a continuous lamination process, provide an extremely cost-effective combination of thermal resistivity and structural integrity. Utilizing innovative chemistry and processing, the excellent performance of PIR boardstock has been sustained, while achieving compliance with recent environmental regulations concerning ozone depletion. Similarly, steel faced polyurethane (PUR) foam panels with fire retardant additives have also come to play an important role in the construction industry. In construction applications, PIR boards and PUR panels are exposed to widely disparate temperature extremes. However, the structural performance of these rigid foams is typically measured only at certain discrete temperatures. Compressive properties are normally measured at room temperature, and often only in one dimension. Dimensional stability is commonly assessed only under one cold (usually-20°F) and one hot/humid condition. The results of such testing are often taken to be representative of a foam's performance under all possible exposure conditions; clearly a bold assumption. This paper details a fundamental investigation into the influence of temperature on the compressive properties and dimensional stability of closed cell rigid foam. It is shown that these critical parameters are dependent on the physical and morphological properties of the polymeric cellular structure, as well as the thermodynamic properties of the gases used to expand the foam. The compressive properties of typical PIR and PUR foams were measured under a wide range of temperatures in three orthogonal directions. This data was fitted into a model based on fundamental material parameters, and the relationship between dimensional stability and compressive strength in an anisotropic foam was examined. Foams expanded with chlorofluorocarbons (CFC's), hydrofluorochlorocarbons (HCFC's), and several zero ozone depletion potential (ODP) blowing agents were evaluated, resulting in a methodology for predicting field performance under a wide variety of environmental exposure conditions. Foam cell morphology can have dramatic influence on foam structural performance. As the dimensional stability of rigid foams is controlled by the mechanical properties in the weakest direction, foams of similar matrix composition and density can exhibit tremendously different dimensional stability performances due to variations in cell orientation. The properties of the blowing agent also play a critical role in dimensional stability. While -20°F was an appropriate test temperature for CFC and HCFC blown foams, other temperatures may be more appropriate for the best possible assessment of zero ODP foam dimensional stability. The role of matrix composition is also significant. PUR foams plasticized by fire retardant additives appeared to exhibit stronger responses to temperature than highly crosslinked PIR foams. Ultimately, an effective combination of matrix strength (chemical composition and density), blowing agents, and processing (minimal cell orientation) for the application in question is the key to dimensionally stable rigid foam. The methodology presented validates the selection of a relatively weak matrix (PUR, low density), in conjunction with an HCFC blowing agent and excellent processing (isotropic cells), for metal faced panels. The methodology also supports the stronger matrix (PIR, higher density), necessary for permeably faced HCFC boardstock, due to the inherent cell orientation which results from the continuous lamination process.

Inadequate fire resistance of polymers raises questions about their advanced applications. Flexible polyurethane (PU) foams have myriad applications but inherently suffer from very high flammability. Because of the dependency of the ultimate properties (mechanical and damping performance) of PU foams on their cellular structure, reinforcement of PU with additives brings about further concerns. Though they are highly flammable and known for their environmental consequences, rubber wastes are desired from a circularity standpoint, which can also improve the mechanical properties of PU foams. In this work, melamine cyanurate (MC), melamine polyphosphate (MPP), and ammonium polyphosphate (APP) are used as well-known flame retardants (FRs) to develop highly fire-retardant ground tire rubber (GTR) particles for flexible PU foams. Analysis of the burning behavior of the resulting PU/GTR composites revealed that the armed GTR particles endowed PU with reduced flammability expressed by over 30% increase in limiting oxygen index, 50% drop in peak heat release rate, as well as reduced smoke generation. The Flame Retardancy Index (FRI) was used to classify and label PU/GTR composites such that the amount of GTR was found to be more important than that of FR type. The wide range of FRI (0.94-7.56), taking Poor to Good performance labels, was indicative of the sensitivity of flame retardancy to the hybridization of FR with GTR components, a feature of practicality. The results are promising for fire protection requirements in buildings; however, the flammability reduction was achieved at the expense of mechanical and thermal insulation performance.

Experiments were performed to characterize the mechanical response of a 15 pcf flexible polyurethane foam to large deformation at different strain rates and temperatures. Results from these experiments indicated that at room temperature, flexible polyurethane foams exhibit significant nonlinear elastic deformation and nearly return to their original undeformed shape when unloaded. However, when these foams are cooled to temperatures below their glass transition temperature of approximately -35 o C, they behave like rigid polyurethane foams and exhibit significant permanent deformation when compressed. Thus, a new model which captures this dramatic change in behavior with temperature was developed and implemented into SIERRA with the name Flex_Foam to describe the mechanical response of both flexible and rigid foams to large deformation at a variety of temperatures and strain rates. This report includes a description of recent experiments. Next, development of the Flex Foam model for flexible polyurethane and other flexible foams is described. Selection of material parameters are discussed and finite element simulations with the new Flex Foam model are compared with experimental results to show behavior that can be captured with this new model.

First introduced in 1954, polyurethane foams rapidly became popular because of light weight, high chemical stability, and outstanding sound and thermal insulation properties. Currently, polyurethane foam is widely applied in industrial and household products. Despite tremendous progress in the development of various formulations of versatile foams, their use is hindered due to high flammability. Fire retardant additives can be introduced into polyurethane foams to enhance their fireproof properties. Nanoscale materials employed as fire-retardant components of polyurethane foams have the potential to overcome this problem. Here, we review the recent (last 5 years) progress that has been made in polyurethane foam modification using nanomaterials to enhance its flame retardance. Different groups of nanomaterials and approaches for incorporating them into foam structures are covered. Special attention is given to the synergetic effects of nanomaterials with other flame-retardant additives.

Flexible polyurethane (PU) foams are easily ignitable and show a high burning velocity, mainly due to their high surface area-to-mass ratio and high air permeability. Consequently, flame retardants such as halogenated compounds are applied. However, the use of halogenated flame retardants is not considered beneficial in transport applications, for example, aviation or automobile, in part due to the high smoke generation. Solid nonhalogenated flame retardants, for example, aluminum trihydroxide (ATH), are known as smoke suppressants. The application of ATH in flexible (PU) foam has not yet been reported in the literature. In this study, the application of different types and amounts of ATH and the resulting structure—property relationship in the foam are investigated. The increase in the viscosity of the filled raw materials during the foaming process and the negative effects of the filler on the mechanical properties of the final foam pose particular problems in the application of ATH. To pass the FMVSS 302 test, high amounts of ATH are necessary. To overcome the mentioned drawbacks, ATH particles are functionalized by 3-aminopropyltriethoxysilane under different conditions. The synthesized products were characterized by Fourier transform infrared, energy-dispersive X-ray fluorescence analysis, and 29Si and 1H solid-state nuclear magnetic resonance spectroscopy. The silane-treated ATH particles show a significant decrease in viscosity of the ATH—polyol system of more than 20% at ATH contents of up to 60 phpp. Values of the rising behavior during foaming and the burning velocity are not affected by this silane treatment. However, the compression test of PU foams with the silane-treated ATH particles show a decrease in compression strength of up to 20% compared to untreated ATH particles in the flexible PU foam. At higher ATH contents, no effect of silanization is observed.

A novel three bilayers nanocoating containing MoS2 nanosheets and C60 was constructed on the surface of flexible polyurethane (FPU) foam by a layer-by-layer assembly method. MoS2 nanosheets were prepared by ultrasonic-assistant exfoliation method in a mixed solvent of N-Methyl-2-pyrrolidinone (NMP) and aqueous hydrogen peroxide (30% H2O2). MoS2-C60/FPU foam was prepared by alternately submerging the FPU foam into C60/guargum and MoS2/sodium alginate suspensions. Scanning electron microscopy (SEM) characterization showed that MoS2 nanosheets and C60 nanoparticles were uniformly distributed on the surface of FPU foam matrix. Thermogravimetric analysis demonstrated that MoS2-C60/FPU foam exhibited better thermal stability than the control FPU foam. Cone calorimeter test results revealed that MoS2-C60/FPU foam with the incorporation of 5.24 wt% MoS2-C60 nanocoating had a remarkable reduction in peak heat release rate (pHRR, 47.5% reduction), total heat released (THR, 51.1% reduction) and total smoke production (TSP, 33.1% reduction) compared with those of the control FPU foam. Furthermore, the morphology and structure of char residue after cone calorimeter test were investigated by SEM and Raman spectroscopy. The possible flame-retardant mechanism of MoS2-C60/FPU foam was proposed, and this significant improvement in flame retardancy could be ascribed to the insulating barrier and adsorption effect of MoS2 nanosheets, free radicals-trapping ability of C60 in condensed phase, and the catalytic carbonization effect of the MoS2-C60 nanocoating. This work provides a new approach for producing high quality flame retardant polyurethane foam materials.

Two series of rigid and flexible polyurethane foams were prepared with two types of silica fillers. The density of the flexible foams was 60 kg/m 3 and that of rigid 30 kg/m3. The fillers were micro-silica of the average particle size of 1.5 mm and nano-silica of the average particle size of 12 nm. The concentration of fillers varied from 0–20%. The micro-silica filler did not show any significant effect on density of either rigid or flexible foams. Nano-silica increased the density of both types of foams only at concentration above 20%. Nano-silica lowered the compression strength of both types of foams at all concentrations while micro-silica exhibited the same effect at concentrations above 10%. The hardness and compression strength in flexible polyurethane foams with nano-silica was increased and the rebound resilience decreased. Reduced density of foams was not changed by nano-silica concentrations up to 20%. It is assumed that the nano-filler, as an additional physical crosslinker, increased modulus of the flexible segment in the polyurethane matrix, resulting in increased hardness and compression strength. The micro-filler in flexible foams lowered hardness and compression strength, but increased rebound resilience. Wide angle X-ray scattering (WAXS) showed amorphous morphology of both flexible and rigid foams filled with nano-silica. WAXS of the micro-silica filled foams showed the presence of randomly oriented crystalline quartz particles and the amorphous structure of the polymeric matrix.

Recently, bio-based polyols are gaining significant attention as sustainable alternatives to petroleum-based polyols for polyurethane (PU) foam production, promoting eco-friendly processing, renewable resource utilization, and reduced CO 2 emissions during polyol synthesis. This report considered fabrication of flexible thermoset PU foam by partially replacing a conventional polyol with a recycled and bio-based polyol from different spent coffee grounds. To resemble properties like cream time, gel time, tack-free time, density, height, and other physical traits of the original foam, different experimental designs have been set up using the design of experiment (DOE) and statistical analysis considering different catalyst and surfactant contents. The effects of silicone surfactant and gelling catalyst with different contents on the physico-mechanical properties of modified with 10 parts by weight (pbw) recovered bio-polyol and unmodified PU foams were investigated. With the desire for higher compressive strength and lower heat shrinkage, the formulations of the bio-polyol-based foams are optimized with 0.75 pbw of catalyst and 1.2 pbw of surfactant amounts. Consequently, at optimized condition, the PU foam displays a compressive strength of 62 gf/cm 2 and the lowest heat shrinkage rate (2.26%). Furthermore, the fabricated foam with unique cellular morphology shows a higher sound absorption coefficient at the lower and higher frequencies than the original foam, signifying its applicability in electric vehicles. Thus, owing to their impressive mechanical and acoustic characteristics, the developed bio-foams could serve as viable alternatives to traditional flexible PU foams for minimizing vibrations and noise pollution.

Halogen-free flame retardant PUF: Effect of melamine compounds on mechanical, thermal and flame retardant properties

Flexible polyurethane foams (FPUF) are commonly used as cushioning material in upholstered products made on several industrial sectors: furniture, automotive seating, bedding, etc. Polyurethane is a high molecular weight polymer based on the reaction between a hydroxyl group (polyol) and isocyanate. The density, flowability, compressive, tensile or shearing strength, the thermal and dimensional stability, combustibility, and other properties can be adjusted by the addition of several additives. Nanomaterials offer a wide range of possibilities to obtain nanocomposites with specific properties. The combination of FPUF with silica nanoparticles could develop nanocomposite materials with unique properties: improved mechanical and thermal properties, gas permeability, and fire retardancy. However, as silica particles are at least partially surface-terminated with Si-OH groups, it was suspected that the silica could interfere in the reaction of poyurethane formation.The objective of this study was to investigate the enhancement of thermal and mechanical properties of FPUF by the incorporation of different types of silica and determining the influence thereof during the foaming process. Flexible polyurethane foams with different loading mass fraction of silica nanoparticles (0-1% wt) and different types of silica (non treated and modified silica) were synthesized. PU/SiO2 nanocomposites were characterized by FTIR spectroscopy, TGA, and measurements of apparent density, resilience and determination of compression set. Addition of silica nanoparticles influences negatively in the density and compression set of the foams. However, resilience and thermal stability of the foams are improved. Silica nanoparticles do not affect to the chemical structure of the foams although they interfere in the blowing reaction.