Surface Of Polyurethane Foam Research Articles

Smoke optical density and transmittance of a polyurethane foam surface treated with aluminum and mineral felt

Smoke optical density and transmittance of a polyurethane foam surface treated with aluminum and mineral felt

Hydrophobic UiO-66 composite: Surface energy modelling for oil-water interactions

Oil spill is considered as the serious threat to aquatic ecosystem and it is quite a challenge to clean such oil spills. In order to cure this problem, we introduced a novel hydrophobic composite material making use of metal organic framework (MOF) i.e., UiO-66 and polyurethane (PU) foam. PU foam was utilized for oil absorption by incorporation of Fe3O4 particles via in-situ approach and dip coating it with polydimethylsiloxane (PDMS) and hydrophobic UiO-66 (hUiO-66) resulting into the formation of hydrophobic composite foam. The decrease in hydrophilic character and increase in hydrophobic character of PU foam was deduced using FTIR and contact angle analysis. PDMS being a low surface energy polymer accounted for the hydrophobicity of the composite material, the coating of PDMS on the material gave contact angle of 122.1°. Furthermore, Fe3O4 provides surface roughness on the surface of PU foam which is clearly visible in FESEM analysis leading to decrease in surface energy of the composite thereby increasing the hydrophobicity and absorption capacity. In order to study the surface area, pore size and pore type of the material, BET surface area analyzer was used depicting surface area of 1049.90 m2g−1 for UiO-66 and 431 m2g−1 for hUiO-66@Fe3O4@PDMS. To gain insight into the surface energy of the composite, various models such as Zisman model, OWRK model and Neumann model were utilized to determine. Moreover, the composite resulted in excellent reusability maintaining the separation efficiency of about 78.4 g/g even after 36 cycles. This shows a substantial improvement in the area compared to previous research and opens the door for the production of hydrophobic foams for purposes like oil-spill cleanup in challenging circumstances. The proposed approach efficiently helpful in oil-spill cleanup, making it promising for oil leakages.

Autotrophic denitrification by sulfur-based immobilized electron donor for enhanced nitrogen removal: Denitrification performance, microbial interspecific interaction and functional traits

Sulfur-driven autotrophic denitrification (SdAD) is a promising nitrogen removing process, but its applications were generally constrained by conventional electron donors (i.e., thiosulfate (Na2S2O3)) with high valence and limited bioavailability. Herein, an immobilized electron donor by loading elemental sulfur on the surface of polyurethane foam (PFSF) was developed, and its feasibility for SdAD was investigated. The denitrification efficiency of PFSF was 97.3%, higher than that of Na2S2O3 (91.1%). Functional microorganisms (i.e., Thiobacillus and Sulfurimonas) and their metabolic activities (i.e., nir and nor) were substantially enhanced by PFSF. PFSF resulted in the enrichment of sulfate-reducing bacteria, which can reduce sulfate (SO42−). It attenuated the inhibitory effect of SO42−, whereas the generated product (hydrogen sulfide) also served as an electron donor for SdAD. According to the economic evaluation, PFSF exhibited strong market potential. This study proposes an efficient and low-cost immobilized electron donor for SdAD and provides theoretical support to its practical applications.

Surface coating of biomass-modified black phosphorus enhances flame retardancy of rigid polyurethane foam and its synergistic mechanism

A novel surface coating based on chitosan (CS) modified black phosphorus (BP) is obtained through layer-by-layer self-assembly and applied to flame-retardant rigid polyurethane foam (PUF). The CS-BP coating tightly adheres to the PUF surface through hydrogen bonding and electrostatic interaction, improving the PUF's thermal stability, photothermal conversion performance and fire safety performance without compromising its mechanical properties. The 9L-CS-BP/PUF exhibits reduced the peak of CO2 release, PHRR, and THR by 36.7%, 39.5%, and 28.8%, respectively, while increasing its residual carbon content by 35.2%. Moreover, a systematic comparison is made between the residual carbon inside and on the surface before and after combustion, and the results indicate that a large number of P-O-C structures and phosphoric acid derivatives are generated on the surface. The surface carbon layer formed by CS-BP effectively inhibited the thermo-oxidative degradation process of inner PUF. In the gas phase, modification of CS increases both the temperature range for the release of phosphorus-containing compounds during BP pyrolysis and the release of non-combustible gases during combustion, synergistically enhancing the gas-phase flame retardancy of CS-BP coating. This study provides a new approach to enhance the flame retardancy efficiency and broaden the application of BP-based flame retardants.

Rigid-flexible coupled polyphosphazene supported polyurethane foam for efficient and selective adsorption of anionic dyes from water

We proposed a feasible strategy to prepare a rigid-flexible coupled polyphosphazene supported polyurethane foam (PUF-PCP) adsorbent by in situ polycondensation between hexachlorocyclotriphosphazene and polyethyleneimine on the surface of polyurethane foam (PUF) at room temperature. Owing to combination of the open cell porous structure of PUF support and the superior adsorption capacity of PCP coatings, the PUF-PCP composite adsorbent exhibited good adsorption behavior towards anionic dyes. Especially, the experimental adsorption capacity of PUF-PCP for methyl orange (MO) dye was up to 978.56 mg g−1 at 25 ºC. The relative separation factors of MO for methylene blue, crystal violet and rhodamine B were 224.1, 78.1 and 161.8 respectively, exhibiting an excellent adsorption selectivity of PUF-PCP towards MO. Moreover, the used PUF-PCP adsorbent can be easily collected and regenerated. The adsorption test data were best explained by Langmuir model and pseudo-second-order model. The adsorption process of MO onto PUF-PCP was spontaneous and endothermic. XPS and FT-IR analysis confirmed that electrostatic adsorption and hydrogen bonding were the plausible uptake mechanism of PUF-PCP for MO molecules. The present work demonstrated that PUF-PCP has promising potential in removing environmental anionic pollutants from waterbody.

Retention and Determination of Polycyclic Aromatic Hydrocarbons from Urban Air Based on Recycled Polyurethane Foam Modified with Expanded Polystyrene

Expanded polystyrene (EPS) and polyurethane foams (PUFs) are widely produced and used due to their properties and, recently, it has been described that polystyrene present π–π interactions. Therefore, this work proposes to use recycled EPS to modify the surface of PUFs for the retention of 12 polycyclic aromatic hydrocarbons (PAHs) in air samples. PUF cylinders were modified with recycled polystyrene and characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, and affinity experiments. The proposed material is suitable for the retention-elution of PAHs from air samples, and can be incorporated to liquid chromatography generating a quantitative methodology. This methodology is efficient, fast and use lower volumes of organic solvents compared with other methodologies. Eighteen urban air samples were collected and analyzed weekly, using principal component analysis (PCA), and a relation between meteorological parameters and concentration of PAHs was observed.

A biomimetic closed-loop recyclable, long-term durable, extreme-condition resistant, flame-retardant nanocoating synthesized by reversible flocculation assembly.

Flame-retardant coatings have attracted increasing attention in mitigating the fire threat of flammable polymer materials. Their durable application inevitably provides high resistance to various complex environments, however, discarded stable materials will turn into another man-made waste disaster. The paradigm shift toward a sustainable future is to combine durability and recyclability of coatings. Herein, we demonstrate a biomimetic coating that reversibly captures active flame-retardant nanomaterials by flocculation assembly using anionic polyacrylamide covering the polyurethane foam surface. Strong hydrogen bonding and microstructural interlocking provide the coating with high durability under complex harsh conditions (underwater, chemical exposure, hydrothermal aging, long-term external extrusion, etc.). Meanwhile, the disassembly/reorganization of the coating can be easily repeated in response to pH stimulation with a recycling rate of 97%. The experiments and theoretical calculations reveal the mechanism of the reversible flocculation assembly. This biomimetic strategy of responsive flocculation assembly opens the way for functional coatings with integrated durability and recyclability.

Polyurethane Foam Incorporated with Nanosized Copper-Based Metal-Organic Framework: Its Antibacterial Properties and Biocompatibility.

Polyurethane foams (PUFs) have attracted attention as biomaterials because of their low adhesion to the wound area and suitability as biodegradable or bioactive materials. The composition of the building blocks for PUFs can be controlled with additives, which provide excellent anti-drug resistance and biocompatibility. Herein, nanosized Cu-BTC (copper(II)-benzene-1,3,5-tricarboxylate) was incorporated into a PUF via the crosslinking reaction of castor oil and chitosan with toluene-2,4-diisocyanate, to enhance therapeutic efficiency through the modification of the surface of PUF. The physical and thermal properties of the nanosized Cu-BTC-incorporated PUF (PUF@Cu-BTC), e.g., swelling ratio, phase transition, thermal gravity loss, and cell morphology, were compared with those of the control PUF. The bactericidal activities of PUF@Cu-BTC and control PUF were evaluated against Pseudomonas aeruginosa, Klebsiella pneumoniae, and methicillin-resistant Staphylococcus aureus. PUF@Cu-BTC exhibited selective and significant antibacterial activity toward the tested bacteria and lower cytotoxicity for mouse embryonic fibroblasts compared with the control PUF at a dose of 2 mg mL−1. The Cu(II) ions release test showed that PUF@Cu-BTC was stable in phosphate buffered saline (PBS) for 24 h. The selective bactericidal activity and low cytotoxicity of PUF@Cu-BTC ensure it is a candidate for therapeutic applications for the drug delivery, treatment of skin disease, and wound healing.

Assessment of gas-phase concentrations of organophosphate flame retardants at the material surface using a midget emission cell coupled to solid-phase microextraction

Actual methods for on-site measurement of gaseous concentrations of Semi-Volatile Organic Compounds (SVOCs) at the material surface (y0) are not yet sufficiently developed mainly due to sampling difficulties. These concentrations are the key data to improve knowledge about indoor sources and human exposure to SVOCs. To the end, a specific emission cell coupled to solid-phase microextraction (SPME) was developed. The main challenge with this method is calibration because of very low volatility of SVOCs and static sampling mode. In this study, a generating system of organophosphate flame retardants (OFRs) using polyurethane foam as source combined with an active sampling method with Tenax tubes was proposed as a novel calibration device for SPME-based method. The generating system delivered stable OFR concentrations after 190 h of operation with a variation not exceeding ±5%. It allowed to obtain robust calibrations for tris-(2-chloropropyl)-phosphate (TCPP) and tri-butyl-phosphate (TBP) measured with the emission cell coupled to SPME-based method, define the optimal sampling requirements and achieve reproducible and accurate measurements of y0 at μg.m−3 level.TCPP and TBP gas-phase concentrations at the polyurethane foam surface (y0) were followed up over more 228 days under controlled temperature conditions. A high stability of these concentrations was observed showing that polyurethane foam acts as a stable and continuous source of organophosphate flame retardants indoors. This novel method should be useful for assessing the dynamic of emissions from indoor sources and potential exposure to SVOCs in indoor environments.

A stepwise separation process for selective recovery of gallium from hydrochloric acid leach liquor of coal fly ash

The interest in gallium (Ga) recovery from coal fly ash has been driven by its rapidly growing demand for manufacturing and its extraction can facilitate the effective use of coal fly ash, which is conducive to reducing the soil degradation and environment danger. In this study, polyurethane foam (PUF) as an adsorbent for Ga(III) recovery was found to exhibit a good structural stability and a high selectivity in a strongly acidic solution. Adsorption measurements show that PUF has a good adsorption ability and its maximum adsorption capacity is 62.53 mg/g. Furthermore, its adsorption behavior can be described well by the pseudo-second-order model. The concentrations of Cl(I) played the key role in the adsorption. Meanwhile, the co-existed Fe(III) in the coal fly ash hydrochloric acid leach liquor (CFAHL) exhibits significant interference to the selective adsorption of Ga(III). Therefore, a stepwise process involving Fe(III) removal and Ga(III) adsorption is proposed for the recovery Ga from CFAHL. At an equilibrium pH of 0, the Fe(III) in the CFAHL can be removed by 1 mol/L P507. Then, the Ga(III) can be quantitatively adsorbed from the CFAHL using PUF with limited co-adsorption of Al(III), Mg(II), and Ca(II). The adsorption capacity of Ga(III) remains steady after PUF is used for more than 10 cycles. Based on the results of IR, XPS and DFT, it is speculated that the Ga(III) is probably coordinated in the form of GaCl3 with the donor O atoms of the urethane group (NHCOO) on the PUF surface. The overall results demonstrate the potential use of PUF for Ga recovery from acidic solutions.

Exceptionally flame-retardant flexible polyurethane foam composites: synergistic effect of the silicone resin/graphene oxide coating

A facile strategy was developed to fabricate flexible polyurethane (PU) foam composites with exceptional flame retardancy. The approach involves the incorporation of graphene oxide (GO) into a silicone resin (SiR) solution, which is then deposited onto a PU foam surface via the dip-coating technique and cured. Fourier-transform infrared spectroscopy, scanning electron microscopy, and Raman spectroscopy measurements demonstrated that the SiR and GO were successfully coated onto the PU skeleton and the intrinsic porous structure of the PU foam remained intact. The effects of SiR and GO on the mechanical and thermal stability and flame retardancy of PU composites were evaluated through compression tests, thermogravimetric analysis, vertical combustion tests, and the limiting oxygen index. The measurement results revealed that the composites (PU@SiR-GO) showed superior flame retardancy and thermal and mechanical stability compared to pristine PU or PU coated with SiR alone. The mechanical and thermal stability and the flame-retardant properties of the PU composites were enhanced significantly with increasing GO content. Based on the composition, microstructure, and surface morphology of PU@SiR-GO composites before and after combustion tests, a possible flameretardance mechanism is proposed. This work provides a simple and effective strategy for fabricating flame-retardant composites with improved mechanical performance.

Determination of Cysteine by Diffuse Reflectance Spectroscopy by Its Influence on the Formation of Gold Nanocomposites Based on Polyurethane Foam

A method is proposed for the determination of cysteine in an aqueous solution by its effect on the formation of gold nanoparticles on the surface of polyurethane foams. The method is based on the interaction of in situ formed gold nanoparticles with cysteine, which results in their stabilization in solution and in a decrease in the color intensity of the nanocomposite detected by diffuse reflectance spectroscopy. The effect of the concentration of the precursor, aurichlorohydric acid, contact time of phases, and the pH of the solution on the sensitivity of cysteine determination is studied. Under the selected conditions, the limit of detection for cysteine was 0.36 μg/mL. A possibility of using the proposed method for the determination of cysteine in brewer’s yeast is demonstrated.

Water-based hybrid coatings toward mechanically flexible, super-hydrophobic and flame-retardant polyurethane foam nanocomposites with high-efficiency and reliable fire alarm response

Flammability feature of combustible polymer foam materials often causes massive casualties and property loss, and it is therefore urgent to develop a green and high-efficiency strategy that can reduce or avoid the fire blaze disasters. Here, an extremely simple water-based coating approach is proposed to prepare mechanically flexible, super-hydrophobic and flame-retardant polyurethane (PU) foam nanocomposites with high-efficiency fire warning response. The hybrid ammonium polyphosphate (APP)/graphene oxide (GO) is decorated onto the PU foam surface via electrostatic interactions followed by surface silane functionalization. Interestingly, the silane and APP molecules present selective distributions on the GO and thus form micro-/nano- rough surface with low water affinity to achieve super-hydrophobicity (e.g. water contact angle of ~158.4°). Meanwhile, such hybrid APP/GO/silane coatings produce synergistic flame resistance for the PU foam materials, which is attributed to the formation of compact and uniform P-Si elements co-covered rGO layer on the foam surface. Further, the hybrid coatings can provide high-efficiency fire warning response under complicated conditions, e.g. flame detection response time of only ~2.0 s and excellent fire early warning time in pre-combustion (e.g. 11.2 s at 300 °C). Therefore, this work provides new perspectives to design and develop multi-functional coatings for fire safety and prevention applications.

Green Flexible Polyurethane Foam as a Potent Support for Fe-Si Adsorbent.

This paper describes the preparation, characterisation, and potential application of flexible palm oil-based polyurethane foam (PUF) as a support for iron-silica (Fe-Si) adsorbent. Fe-Si/polyurethane composite (Fe-Si/PUC) was prepared by impregnating Fe-Si adsorbent onto the surface of PUF by using a novel immersion-drying method. Morphological analysis of Fe-Si/PUC proved that Fe-Si was successfully impregnated onto the surface of PUF. Compression test and thermogravimetric analysis were carried out to determine the flexibility and thermal stability of Fe-Si/PUC, respectively. The Fe-Si/PUC removed 90.0% of 10 ppm methylene blue (MB) from aqueous solution in 60 min. The reusability study showed that Fe-Si/PUC removed 55.9% of MB on the seventh cycle. Hence, the synthesis of Fe-Si/PUC opens up a new path of implementing palm oil-based PUF to assist in the recovery of an adsorbent for environmental clean-up. The mechanism of physical interaction during the impregnation of Fe-Si adsorbent onto PUF was proposed in this paper.

Biological treatment of high salinity and low pH produced water in oilfield with immobilized cells of P. aeruginosa NY3 in a pilot-scale

Produced water (PW) in oilfield, as the largest waste streams in the oil and gas production, has posed a huge threat to the ecosystem. In this work, an environmentally friendly and recyclable biofilms have been developed for treating PW. We discovered that the cells of P. aeruginosa NY3 could be easily immobilized on the surface of polyurethane foam (PUF). Removal efficiency of oil and suspended solids (SS) by immobilized P. aeruginosa NY3 was keeping above 80% and 76% both in a laboratory scale and a pilot scale under suitable pH. Low pH and high value of SS had negative effect on the degradation of oil and SS by P. aeruginosa NY3. Recovery test showed that, the activity of biofilms P. aeruginosa NY3 after running in a pilot scale could be recovered in 5 days. Removal ability of oil in the real PW by the recovered biofilms of P. aeruginosa NY3 was even higher than that of the freshly prepared biofilms. These results indicated that, with a simple pH adjustment, immobilized P. aeruginosa NY3 could be recycled for removing oil and SS in the raw PW resulted from oil production.

Hierarchically porous SiO2/polyurethane foam composites towards excellent thermal insulating, flame-retardant and smoke-suppressant performances

Polyurethane foam (PUF) is widely used in building insulation field but highly flammable. In an effort to develop an efficient way to reduce flammability and smoke release of PUF without sacrificing its inherent merits, a novel strategy has been proposed to decorate silica aerogels onto the surface of PUF to fabricate hierarchically porous SiO2/PUF composites. Due to the unique hierarchically porous structure, the resultant composites showed superior thermal insulation with a lower thermal conductivity of 0.0282 W/(m K). The introduction of silica aerogels also effectively improved the compressive strength, almost 220% of that of neat PUF. Notably, the SiO2/PUF composites were rendered self-extinguishing in vertical burning tests and had a high limiting oxygen index (LOI) value of 32.5%. Cone calorimetry (CC) tests revealed that the peak heat release rate (PHRR) and peak smoke production release (PSPR) of the SiO2/PUF composites were reduced by 40.4% and 45.6%, respectively. Particularly, the specific optical density (Ds) of the composites displayed as 55.7% reduction in the smoke density chamber tests, showing excellent smoke-suppression. The mechanism analysis suggested that a compact silica-rich hybrid barrier formed, preventing thermal degradation products and energy transfer during combustion. These results indicate SiO2/PUF composites have enormous potential as building insulation materials.

Bi-phase fire-resistant polyethylenimine/graphene oxide/melanin coatings using layer by layer assembly technique: Smoke suppression and thermal stability of flexible polyurethane foams

In an effort to achieve a high-efficient fire-resistant coating for the flexible polyurethane (PU) foams, a layer-by-layer assembly technique of polyethylenimine (PEI), graphene oxide (GO) and synthetic melanin nanoparticles (SMNPs) was constructed on the surface of PU foams. The preeminent radical scavenging capacity and high-temperature thermal stability of SMNPs enable it to be applied as a flame retardant for the subsequent coating process. Scanning electron microscope (SEM) images indicate that the as-fabricated PEI/GO/SMNPs coatings are uniformly deposited on the PU foam along the cell walls. In contrast with pure and bilayer-coated (BL-coated) PU foams, thermogravimetric analysis (TGA) reveals that the trilayer-coated (TL-coated) foam exhibits a better thermos-oxidative stability and a lower pyrolysis rate with the deposition of PEI/GO/SMNPs nanocoating. In the torch burn test, the flame of PU-1TL foam coated with only one-trilayer PEI/GO/SMNPs is able to self-extinguish and the original shape of the entire foam is intactly preserved. Cone colorimeter tests indicate that the release amount of heat and smoke can be effectively suppressed in the coated foam, and the formation of the highly graphitized char is beneficial to the improvement of the fire-resistant performance. In addition, thermogravimetric analysis/infrared spectrometry (TG-IR) results demonstrate that the volatilization of organic and toxic gases in gas phase are effectively restrained, which can be attributed to the lamellar shield of GO and radical trapping effect of SMNPs. These results illustrate that synthetic melanin material is one of the promising candidates as efficient additive in fire-resistant polymers, and the PEI/GO/SMNPs coatings play a part in gas-solid phase to improve the flame retardancy of PU foams.

Stretchable Nanocomposite Conductors Enabled by 3D Segregated Dual‐Filler Network

AbstractFlexible and stretchable electrical conductors are needed in a wide range of applications to maintain electrical conductance under large deformation. Herein a new type of stretchable electrical conductor capable of large deformation is reported. Using a simple and cost‐effective dip‐coating technique, conductive nanomaterials including sliver nanowires (AgNWs) and carbon nanofibers (CNFs) are deposited onto the surface of polyurethane foam, forming a 3D segregated conductive network. The pores are subsequently infused with elastomeric polymethylsiloxane. Upon curing, the resultant nanocomposite is highly conductive even under large strain. Compared with nanocomposites made of a single type of conductive nanomaterial, the nanocomposite obtained by sequential dip‐coating with AgNWs and then CNFs give the best performance, due to the synergetic effect between the two conductive nanomaterials. This highly conductive nanocomposites can withstand large mechanical deformations, including stretching, twisting, and bending while maintain its high electrical conductivity. With a low‐cost and simple fabrication process, these newly developed conductive nanocomposites offer a new type of stretchable conductors for wearable electronics.

Label-free gold nanoparticle-based sensing of cysteine: New peculiarities and prospects

In this article, some new peculiarities and prospects of cysteine determination using aggregation of label-free gold nanoparticles (AuNPs) are described. Features of the aggregation both in solution and on polyurethane surface are compared. Effects of ethylenediaminetetraacetate (EDTA) and cysteamine on the aggregation of AuNPs, which increase sensitivity, are considered. In case of EDTA, it was simultaneously possible to eliminate interferences from cations of metals. It is shown that attaching AuNPs onto polyurethane foam surface changes their sensitivity and selectivity, which can be used for the determination of cysteine. Based on found peculiarities, new methods for the determination of cysteine in a range 0.06–0.5 μg mL−1 (LOD = 0.04 μg mL−1) by spectrophotometry, and 0.02–0.15 μg mL−1 (LOD = 0.01 μg mL−1) by diffuse reflectance spectroscopy were developed.

Electrically conductive graphene-coated polyurethane foam and its epoxy composites

Abstract A facile method is presented to manufacture electrically conductive graphene-coated polyurethane foam (GPF) by dip-coating polyurethane (PU) foams in a graphene (GN) aqueous suspension containing cellulose nanowhisker (CNW) as dispersion assistant. The electrical conductivity of the GPF/epoxy composites reaches 2.46 S/m at a relatively low GN content (0.9 wt%), and the electrical percolation threshold is around 0.3 wt%. The structure observations reveal that the high electrical conductivity results from the 3D networks formed by GN nanosheets coated on the inner surface of PU foams. Moreover, CNW is a key factor to facilitate the formation of GN networks on the PU skeleton. The highest electrical conductivity is obtained at the CNW / GN weight ratio of 1:20.