Synthesis Of Foams Research Articles

Synthesis and enzymatic recycling of sugar-based bio-polyurethane foam

Polyurethane foam (PUF) was prepared by reacting sugar with polyisocyanate and blowing using CO2 formed by reacting polyisocyanate with water. The optimum foaming rate of 840% was obtained at 15 wt% of sugar, and the synthesis and cellular structure of polyurethane were confirmed from Fourier-transform infrared (FT-IR) spectra and scanning electron microscopy (SEM) images. The apparent density and thermal conductivity of the optimized PUF were 0.114 – 0.126 g/mL and 0.049 – 0.053 W/(mK), respectively. At 15 wt% of sugar, the normalized compressive strength of PUF was 17.68 MPa/(g/mL) at 70% strain. PUF was degradable and recyclable by an enzymatic reaction in water using invertase. The degradation reactions using invertases were kinetically analysed. Furthermore, the product of enzymatic decomposition of PUF could be recovered and reused as PUF. This study demonstrated the possibility of synthesizing eco-friendly polymers using sugar and reusing them by enzymatic green recycling.

Synthesis of impermeable cellular glass foam from soda lime glass waste using SiC foaming agent

Synthesis of impermeable cellular glass foam from soda lime glass waste using SiC foaming agent

Synthesis of 3D graphitic carbon foams via pressurized pyrolysis of Victorian brown coal as anode material for Li-ion battery

This study investigates an alternative utilization of earth-abundant Victorian brown coal (BC) for carbon foam preparation and its application in LIBs. Carbon foams (CFs) from blends of Victorian BC and coal tar pitch (CTP) were synthesized through pressurized pyrolysis. The effects of blending ratio and pyrolytic pressure on pore structure transition were systematically studied by SEM and micro-computed tomography beamline (micro-CT) followed by 3D modeling analysis. Furthermore, catalytic graphitization coupled with air activation were used to tailor the structure of CFs as anodic materials for LIBs. The impacts of carbon microstructure and hierarchical pore structure of CFs on the electrochemical performance of LIBs were investigated. The battery test of porous graphitic CFs exhibited an enhanced LIBs performance of 463.1 mAh/g under the current density of 0.1 A/g compared to CFs without treatments. There was 71.49% retention after 1000 cycles at 1 A/g, and the coulombic efficiency remained at 99.99%.

Polyurethane foams from vegetable oil-based polyols: a review.

Polyurethane is a versatile material that can be converted into various forms according to applications. PU foams or PUFs are the most commonly used polyurethanes. These are materials of low density and low thermal conductivity that make them highly suitable for thermal insulating applications. Most of the synthesis of PUFs is still based on the petrochemical industry. There are issues associated with the oil industry, such as environmental pollution, sustainability, and market instability. More recently, we have experienced the COVID-19 pandemic which has destroyed the global supply chain of raw materials. Such sudden disruption of the supply chain affects the global economy. To eliminate the reliance on special ingredients, it is important to find and produce alternate and domestic raw materials. Vegetable oils are organic, cost-effective, and economically viable and present in abundant amounts. The oil consists of triglycerides. It can be functionalized to provide polyol for PU foam synthesis. Herein, we review the literature on factors influencing the properties of PUFs depending on polyols from vegetable oil as well as present a glimpse of the conversion of vegetable oils into polyols for PUF synthesis.

Foam Synthesis of Nickel/Nickel (II) Hydroxide Nanoflakes Using Double Templates of Surfactant Liquid Crystal and Hydrogen Bubbles: A High-Performance Catalyst for Methanol Electrooxidation in Alkaline Solution.

This work demonstrates the chemical synthesis of two-dimensional nanoflakes of mesoporous nickel/nickel (II) hydroxide (Ni/Ni(OH)2-NFs) using double templates of surfactant self-assembled thin-film and foam of hydrogen bubbles produced by sodium borohydride reducing agent. Physicochemical characterizations show the formation of amorphous mesoporous 2D nanoflakes with a Ni/Ni(OH)2 structure and a high specific surface area (165 m2/g). Electrochemical studies show that the electrocatalytic activity of Ni/Ni(OH)2 nanoflakes towards methanol oxidation in alkaline solution is significantly enhanced in comparison with that of parent bare-Ni(OH)2 deposited from surfactant-free solution. Cyclic voltammetry shows that the methanol oxidation mass activity of Ni/Ni(OH)2-NFs reaches 545 A/cm2 gcat at 0.6 V vs. Ag/AgCl, which is more than five times higher than that of bare-Ni(OH)2. Moreover, Ni/Ni(OH)2-NFs reveal less charge transfer resistance (10.4 Ω), stable oxidation current density (625 A/cm2 gcat at 0.7 V vs. Ag/AgCl), and resistance to the adsorption of reaction intermediates and products during three hours of constant-potential methanol oxidation electrolysis in alkaline solution. The high-performance electrocatalytic activity of Ni/Ni(OH)2 nanoflakes is mainly derived from efficient charge transfer due to the high specific surface area of the 2D mesoporous architecture of the nanoflakes, as well as the mass transport of methanol to Ni2+/Ni3+ active sites throughout the catalyst layer.

One-step foam assisted synthesis of robust superhydrophobic lignin-based magnetic foams for highly efficient oil-water separation and rapid solar-driven heavy oil removal

Taking effective measures to remove oil and organic pollutants from water has become a top priority. In this study, we developed a novel superhydrophobic and magnetic lignin-based polyurethane foam for highly efficient adsorption of organic pollutants and removal of viscous crude oil from water. The superhydrophobic bio-based magnetic foam was prepared by the addition of Fe3O4 nanoparticles during the foaming process followed by the immersion in an octadecyltrimethoxysilane (OTMS) solution. After modification by OTMS, the water contact angle (WCA) of the foam adsorbent was increased by 37.1°, exhibiting a high WCA of 156°. Fe3O4 nanoparticles endowed the foam with excellent photo-thermal performance, allowing the efficient adsorption of both crude oil and a wide range of organic solvents. The foam adsorbent had a high adsorption capacity up to 18.8 times of its own weight. The bio-based adsorbent could still retain a high adsorption capacity after over ten cycles. The magnetic property facilitated control and recycling of the foam adsorbent by using a magnetic field. Moreover, the bio-based foam adsorbent was fully degraded in a methanol/sodium hydroxide solution (0.5 mol/L) at 60 °C after 8 h. The outstanding mechanical stability, reusability, and environmental friendliness make these bio-based foam adsorbent highly promising for cleaning up pollutions in water.

Synthesis, antibacterial activity, and enzymatic decomposition of bio-polyurethane foams containing propolis

Polyurethane foam (PUF) is formed by reacting sugar, propolis, and polyisocyanate, and then blowing with CO2, formed by reacting polyisocyanate with water. An optimum foaming rate of 1440% was found for 15 wt.% of sugar and 20 wt.% of propolis, and the synthesis and cell structure of polyurethane were analyzed by scanning electron microscopy (SEM) and Fourier transform infrared (FT-IR) spectroscopy. Under the optimized conditions, the apparent density and thermal conductivity of the PUF-containing propolis were 0.04 – 0.147 g/mL and 0.028 – 0.029 W/(mK), respectively. The bacterial reduction rate was 92.7% in the PUF containing 20 wt.% propolis. PUF can be broken down by enzymatic reactions in water using invertase. The degradation reaction of invertase was kinetically analyzed. This study showed that eco-friendly polymers can be synthesized using sugar and propolis and decomposed through antibacterial activity and enzymatic green recycling.

Cascade (Dithio)carbonate Ring Opening Reactions for Self-Blowing Polyhydroxythiourethane Foams.

Polyurethane (PU) foams are very common materials that have found many applications over the years. Their use is constantly improving due to their unique physical properties and easy blowing which does not require the addition of a blowing agent. Greener routes have been explored in the recent years to replace isocyanates. One of the most promising routes is leading to polyhydroxyurethanes (PHU). However, with PHUs, external blowing agent are usually required to obtain a foam. Thus, the work focuses on PHU foam synthesis using in situ reaction to produce NIPU foam. Hence, the aminolysis of thiocyclic carbonate triggers Pearson reaction between released thiols and cyclic carbonates which serves as a chemical blowing agent.

Controllable synthesis of a robust sucrose-derived bio-carbon foam with 3D hierarchical porous structure for thermal insulation, flame retardancy and oil absorption

The fast exhaustion of the fossil fuels has led to an imperious need for more energy-efficient and environmentally friendly strategies to develop the carbon materials with high structural efficiency and multi-functional integration. Sucrose represents a promising biomass source for obtaining the carbon foams. However, the uncontrolled foaming restricts the preparation and performance of the efficient sucrose-based carbon foams. Herein, a novel route of template-free mechanical foaming-gel has been reported to fabricate the robust and multifunctional sucrose-derived carbon foams with the hierarchical porous structure. The pore structure and porosity could be flexibly controlled by tuning the sucrose concentration during the mechanical stirring process. The synergy between sucrose and epoxy hydrogel as a network skeleton endowed the carbon foams with a high carbon yield (44.7%) and optimal specific mechanical properties. The carbon foams after heat treatment at 1200 °C displayed a low density (0.089–0.195 g/cm3) and a high compression strength (1.02–4.93 MPa). The foams also exhibited excellent heat insulation performance and flame retardancy. The thermal conductivity of the carbon foam with a density of 0.089 g/cm3 was as low as 0.092 W/m·K at room temperature and 0.269 W/m·K at 1200 °C under argon atmosphere. Furthermore, the carbon foams revealed a high oil absorption capacity, together with an optimal recyclability on combustion. Meanwhile, the foams also maintained superhydrophobicity after immersion in acidic, alkaline and salty media for 120 days. The developed strategy could not only realize the preparation of the energy-efficient and environmentally-friendly bio-carbon foams with a reliable self-adaptability to the extreme environments, but also exhibited promising universality and flexibility in designing the carbon materials for applications in aerospace and oil spill cleanup.

A processable Prussian blue analogue-mediated route to promote alkaline electrocatalytic water splitting over bifunctional copper phosphide.

Prussian blue analogues (PBAs) as a class of metal-organic frameworks demonstrate a promising platform to develop cost-effective high-performance electrocatalysts. However, the construction of delicate micro/nanostructures and controllable doping are still a challenging task for the fabrication of highly efficient copper-based electrocatalysts. Herein, we report a facile synthesis of copper foam supported Cu3P@Co-Cu3P (CH@PBA-P/CF) sub-microwire arrays as an active electrocatalyst for alkaline water splitting. The Co-Cu3P shell derived from the Cu3[Co(CN)6]2 PBA serves as the source of active sites. Co doping and construction of core-shell structures endow the CH@PBA-P/CF electrocatalyst with abundant catalytic sites, enhanced intrinsic activity, and low charge transport resistance. The catalytic electrode integrated with 3D copper foam and 1D sub-microwire arrays is highly conductive and stable, which promotes the charge transport and improves the structural stability. As a consequence, CH@PBA-P/CF shows impressive catalytic performances toward the HER and OER in terms of low overpotentials of 231 and 312 mV at a current density of 50 mA cm-2 in 1 M KOH, respectively. Notably, the water electrolyzer using the CH@PBA-P/CF electrode exhibits better water splitting performance than the one using noble metal-based couples.

Preparation of rigid polyurethane foam from lignopolyol obtained through mild oxypropylation.

Lignin, one of the main components of lignocellulose, can be used as an alternative to chemical polyols in the production of polyurethane because of its abundant phenolic and alcohol hydroxyls. Traditionally, lignin is directly applied in the preparation of polyurethane; however, modified lignin has been proved to be superior, especially that obtained by the oxypropylation reaction. Therefore, lignopolyol obtained by mild and efficient oxypropylation was utilized in the production of rigid polyurethane foam in this study. Specifically, the effects of the content of lignopolyol on the chemical structure, morphological structure, mechanical properties and thermal stability of the lignin-based rigid polyurethane foam were investigated. It was found that the compressive strength of the rigid polyurethane foam was significantly improved with the addition of lignopolyol compared with that of the pure polyurethane foam, which was attributed to the fact that oxypropylation made lignin into highly branched and functionalized polyols by transforming all phenolic hydroxyls into aliphatic hydroxyls. Moreover, when the molal weight of lignopolyol accounted for 40% of the added polyols, the generated foam showed optimal uniformity and regularity, and the compressive strength reached 0.18 MPa, meeting the requirements of industrial application, below which, the amount of undesired reactions is bound to increase. As a consequence, the added amount of lignopolyol was increased as much as possible on the basis of guaranteeing the desired properties, which was more conducive to realizing the green degradation and economic synthesis of rigid polyurethane foam.

Performance of geopolymer foams of blast furnace slag covered with poly(lactic acid) for wastewater treatment

This research investigated a new method to produce geopolymer foams from blast furnace slag (BFS) with poly(lactic acid) (PLA) covering the developed porosity into the materials. A porous alkali-activated material was developed, and a biodegradable polymer was used to cover the geopolymer in the bulk state. Geopolymer foams were synthesized with a sodium metasilicate solution, and the porosity was developed by adding hydrogen peroxide (H 2 O 2 ). Foams of materials were produced with two stoichiometries of 1.4 and 1.6 g/L between solid/liquid with a hydrogen peroxide solution. The dimensional stability was achieved after coating geopolymer foams with PLA, improving the molding capacity on different geometries for the composite materials. Specimens of the geopolymer foam/PLA composites were characterized by X-ray fluorescence (XRF), Fourier transformed infrared (FTIR), thermogravimetry (TGA), and field emission gun scanning electron microscopy (FEG-SEM). The permeation analysis of metal oxide particles through the composites foam specimens was performed using water dispersions containing bismuth oxide or titanium oxide. The test resulted in high performance in the retention of particulate materials. The highlights of the results indicated the efficiency in the synthesis of geopolymer foam, a good formation of porosity, and an effective PLA coating on the internal interfaces of geopolymer foam through the development of a new bulk state coating method, improving the dimensional stability and the retention of bismuth and titanium oxides particles by the produced geopolymer foams for water depollution.

Synthesis of photocatalytic pore size-tuned ZnO molecular foams

MolFoams, photocatalytic foams synthesised via sol gel to form a continuous monolith free from discrete particles, effectively removed carbamazepine, a known organic micropollutant, outperforming both slurries and supported photocatalysts.

A study on coconut fatty acid diethanolamide-based polyurethane foams.

The possibility of using coconut fatty acid diethanolamide, a derivate from coconut oil as a bio-based polyol for the synthesis of polyurethane foam was explored. The intrinsic tertiary amine moiety in this polyol (p-CFAD) endowed an auto-catalytic effect in the synthesis process of polyurethane foams, combined with a shorter cream and gelation time compared to the fossil-based polyol 3152. H-nuclear magnetic resonance (1H-NMR) and Fourier transform infrared spectrometry (FTIR) were conducted to characterize the chemical structural features of the p-CFAD, and rheology measurement showed the shear-thinning behavior due to the branched structure. A thermal conductivity comparable to the commercial rigid polyurethane foam was achieved when 40wt% fossil-based polyol 3152 was substituted with the bio-based p-CFAD. With the increased content of the p-CFAD, a transition of the physical properties from rigid PU foam to soft PU foam was observed. Scanning electron microscopy (SEM) revealed the occurrence of the interconnected pores on the cell walls with the increase of the added p-CFAD, implying the possibility of regulating the cellular structure and foam properties via the incorporation of the p-CFAD. Results showed the feasibility of using p-CFAD as a potential polyol in the development of bio-based polyurethane foams with high performance.

Comparison of dehydration methods for untreated lignin resole by hot air oven and vacuum rotary evaporator to synthesize lignin-based phenolic foam

We investigate two different dehydration methods to determine their suitability for preparing resoles for foam synthesis. A simplified process for synthesizing lignin foam (LF) from lignin resole (LR) dehydrated in a hot air oven (HAO) is compared with that dehydrated using a vacuum rotary evaporator (VRE). First, the LR formulation is prepared by mixing phenol with untreated lignin (0%–15% by weight), and subsequently, the prepared LRs are dehydrated using an HAO and a VRE. We find that for the same dehydration time, both techniques yield LRs with the same chemical compositions; however, the HAO technique affords a moisture removal of 13–17% by weight, whereas the VRE technique removes 9–12% moisture by weight. The LR obtained by the HAO is more viscous and maintains a circular shape after being dropped on a plate. In our experimental synthesis of LF containing VRE resole, biofoam is not formed owing to insufficient viscosity, whereas biofoam is obtained with the HAO resole. The synthesized LF exhibits a density range of 44.96–85.68 kg/m3 and a compressive strength of 103.28–152.27 kPa. Scanning electron microscopy investigations show that the morphology of the foam is a closed-cell structure. The simplified synthesis of LF from the HAO-treated resole offers significant advantages over the complexity of the conventional VRE approach in terms of equipment cost and energy consumption. The resulting foam exhibits a thermal stability and thermal performance comparable with the counterpart properties of phenolic foam.

Foamed geopolymers for fire protection: Burn‐through testing and modeling

SummaryGeopolymer (GP) foam as a fire protective coating was synthesized, deposited on a steel plate, hardened and evaluated using a burn‐through test at a reduced scale. It was shown that the GP foam acts as an efficient fire barrier (with 250°C reduction compared to virgin steel evaluated in the same conditions). A numerical model using Comsol Multiphysics (finite element code) was performed to simulate the fire behavior of the GP foam. It was based on the complete characterization of the GP foam to provide accurate input data for the model. The latter captures well the temperature rise, including the endothermal effect due to water vaporization. A parametric study of the porosity and the emissivity at the surface of the GP foam brings new insights to optimize the performance of the GP foam. It is shown that a porosity of 90% and an emissivity lower than 0.75 should provide the highest performance to GP foam. The fabrication of an optimized GP foam is feasible using a technology of low emissivity thin coating and by adjusting the synthesis of the GP foam to increase its porosity.

Reduction in Noise Pollution of a Gas Power Plant under Construction Using Synthesis of Copper and Nickel Alloy Foam in a Simulated Setting

Noise pollution is one of the challenges of installing equipment and developing industries. The control of noise generated by small power plants is a necessity for its use development. Designing the synthesis of copper and nickel alloy foam and using this foam to reduce noise pollution in the exhaust is one of the effective methods to control and reduce noise pollution from power plants. The purpose of this study was to synthesize copper and nickel alloy foam and compare the effect of results of spl changes in software ANSYS for three ductless, ideal wall and multilayer wall modes at different frequencies. In this regard, the adjunct duct is modeled as 3D by software ANSYS, and the output sound intensity of the duct in the acoustic setting is analyzed in several different modes. The results show that three different modes in the exhaust output indicate that the multilayer wall at most frequencies reduces the sound pressure level relative to the ductless or ideal wall modes.

An insight into the role of biomass, biocompounds and synthetic polymers as additives to coal for the synthesis of carbon foams

Carbon foams were synthesized from blends of coal and several C-containing additives of different nature, with the aim to study their influence on the foaming step, and hence in the final properties of the obtained foams. The additives included biomass and agricultural products, and thermoplastic and thermosetting polymers, at different concentrations, ranging from 5 to 20 wt%. The effects of the additives on pore structure, carbon matrix and thermal properties of the resulting foams were investigated. The presence of additives during pyrolysis had no effect on the yield of carbonaceous product. However, all the additives, except the polybutadiene phenyl terminated (PBP) elastomer, led to a reduction in the fluidity of the blend. This difference in the effect can be related to the liquid nature of PBP, which favors the impregnation of coal particles, to the decomposition pattern overlapping with that of the coal, and to a high chemical affinity of the degradation products of PBP and coal. Analysis of the fluidity development of the blends and the changes in volatile matter production at different temperature intervals showed that bio-type additives with the maximum emission of volatiles in the coal pre-plastic stage provided improvements in the porosity of the C-foams. In contrast, synthetic polymers like low-density polyethylene (LDPE) and PBP generated most of their thermal degradation products during the plastic and the own thermal degradation stages of coal, leading to a reduction in the porosity of the carbon foams. This behavior can be attributed to a blocking of some macropores in the C-foams by deposition, in the pore mouths, of molten LDPE and/or oligomers from its backbone promoted by the conditions applied during the long residence time inside the reactor. The addition of polyethylene terephthalate (PET) resulted in no foam formation. Regardless of the additive, the resulting foams derived from binary blends showed lower thermal conductivity compared to that synthesized from the unmixed coal. The values of thermal conductivity are closely related to the porous and carbon structure displayed by the foams.

Facile fabrication of the porous adsorbent from natural plant Angelica Sinensis stabilized liquid foam for dye removal

Porous materials as emerging high-efficiency adsorbents have attracted increasing attention in recent years, due to the high specific surface area, fast adsorption rate, favorable adsorption capacity to heavy metal, dyes, and other pollutants, etc. Among various approaches, the foam template method with the advantage of flexible operation and controllable pores structure is proposed to prepare net type of porous adsorbents with superior adsorption capacity and rapid adsorption rate. In this process, natural plant Angelica Sinensis (AS) was treated with a simple alkaline-heat process, and the resultant product was used firstly to prepare foam with high stability, and the positive effect of the cellulose dissociation and the conversion of ligustilide into amphiphilic moleculars on improving the stability of Pickering foam was revealed. The liquid foam can serve as pore-foaming template and precursor of polymerization for synthesizing porous adsorbent by one-step integrated process of free radical polymerization and silane hydrolysis. The porous adsorbent showed the sufficient porous structure and excellent adsorption performance for cationic dye, with maximum adsorption capacities of 386.13 mg g-1 and 284.20 mg g-1 for methyl violet (MV) and malachite green (MG). In a word, the novel approach can provide an important reference for green synthesis of high stable foam and the superporous material, and the adsorbent showed great application potential in the field of water treatment.

Cellulose nanocrystals supported—PolyHIPE foams for low‐temperature latent heat storage applications

AbstractParaffin‐based shape‐stabilized composite phase change materials (PCM) containing surface modified cellulose nanocrystals (CNCs) for thermal energy storage applications were prepared. In this respect, a three‐step experimental procedure consisting nanoparticle modification, macroporous foam synthesis, and composite PCM preparation was implemented. While CNCs were modified via freeze‐templating, high internal phase emulsion (HIPE) templating was used for the synthesis of polymeric foams ‐ known as polyHIPEs. Meanwhile a simple method was applied to impregnate n‐hexadecane (HD), which is a paraffin‐based PCM within the polyHIPE foam matrix. It was demonstrated that surface modified CNCs can be efficiently used to prepare polyHIPE foams with improved properties. It was also shown that the impregnation of HD into the ‐polyHIPE foam matrix supported by CTAB‐CNCs can be achieved with an incorporation rate of up to 55.7%. Moreover, the phase transition temperature and thermal energy storage capacity of the obtained composite PCM was determined as 22.7°C and 117 J/g, respectively.