Synthesis Of Foams Research Articles

Rigid Polyurethane Foam Obtained from Enzymatic Glycerolysis: Evaluation of the Influence of Lipase on Biopolyol Composition and Polymer Characteristics

In this study, the synthesis of biopolyols derived from castor oil and glycerol was performed by enzymatic glycerolysis in a solvent-free system applying the lipases: Novozym® 435 (N435), from Candida antarctica fraction B, immobilized on macroporous anionic resin, and Eversa® Transform 2.0, a soluble formulation from Thermomyces lanuginosus. The biopolyols presented different conversion into mono- and diacylglycerol (MAG and DAG) owing to regioselectivity of the lipases. The resulting biopolyols were employed for the synthesis of polyurethane foams using different amounts of chemical blowing agent (water). The NCO source employed was polymeric methylene diphenyl diisocyanate (pMDI). The foams were compared, and the results showed that the PU foams obtained by using the biopolyol from lipase N435 presented uniform pore size and more desirable mechanical characteristics. Although this has arisen, the results obtained by using the lipase Eversa® Transform 2.0 showed the possibility of applying a low-cost enzyme to obtain biopolyols and foams, and there may be a possibility of competition with chemical catalysts.

Glycolysis of Polyurethanes Composites Containing Nanosilica.

Rigid polyurethane (RPU) foams have been successfully glycolyzed by using diethylene glycol (DEG) and crude glycerol (CG) as transesterification agents. However, DEG did not allow to achieve a split-phase process, obtaining a product with low polyol purity (61.7 wt %). On contrary, CG allowed to achieve a split-phase glycolysis improving the recovered polyol purity (76.5%). This is an important novelty since, up to now, RPUs were glycolyzed in single-phase processes giving products of low polyol concentration, which reduced the further applications. Moreover, the nanosilica used as filler of the glycolyzed foams was recovered completely pure. The recovered polyol successfully replaced up to 60% of the raw polyol in the synthesis of RPU foams and including the recovered nanosilica in the same concentration than in glycolyzed foam. Thus, the feasibility of the chemical recycling of this type of polyurethane composites has been demonstrated. Additionally, PU foams were synthesized employing fresh nanosilica to evaluate whether the recovered nanosilica has any influence on the RPU foam properties. These foams were characterized structurally, mechanically and thermally with the aim of proving that they met the specifications of commercial foams. Finally, the feasibility of recovering the of CG by vacuum distillation has been demonstrated.

Vegetable Fillers and Rapeseed Oil-Based Polyol as Natural Raw Materials for the Production of Rigid Polyurethane Foams.

The reported study concerns the introduction of renewable raw materials into the formulation of rigid polyurethane foams in the quest for the sustainable development of polymer composites. In this study, rigid polyurethane foam composites were prepared using 75 wt.% of rapeseed oil-based polyol and 15 parts per hundred parts of polyol (php) of natural fillers such as chokeberry pomace, raspberry seeds, as well as hazelnut and walnut shells. The influence of the used raw materials on the foaming process, structure, and properties of foams was investigated using a FOAMAT analyzer and a wide selection of characterization techniques. The introduction of renewable raw materials limited reactivity of the system, which reduced maximum temperature of the foaming process. Moreover, foams prepared using renewable raw materials were characterized by a more regular cell structure, a higher share of closed cells, lower apparent density, lower compressive strength and glass transition temperature, low friability (<2%), low water absorption (<1%), high dimensional stability (<±0.5%) and increased thermal stability. The proper selection and preparation of the renewable raw materials and the rational development of the polyurethane recipe composition allow for the preparation of environmentally-friendly foam products with beneficial application properties considering the demands of the circular economy in the synthesis of rigid foams.

Synthesis of graphene foams and their sorption properties of n-hexane

The influence of preparation conditions of the graphene foams on their physicochemical properties is shown. Different graphene aerogels were obtained from various graphene oxide water suspensions using the hydrothermal method (with or without the addition of acrylic microemulsion and varying in drying time—24 and 48 h). Prolonged drying of the hydrogels resulted in smaller pores in the foams. The composition of graphene oxide (GO) and acrylic polymer water suspensions leads to the smallest surface area which is due to the closing of the pores of the composite structure. Thermal treatment of samples at 950 °C removed the polymer residues. The heating process increased the surface area and the total pore volume of all samples, which were used to test the graphene foams (GFs) for adsorption of n-hexane. These tests have shown that the most effective samples for n-hexane adsorption were the samples where for the preparation of the composite GO and acrylic resin were used. The best of obtained samples adsorbed 415 mg g−1 of n-hexane which is a better result than for activated carbon manufactured from natural cork. Further preparation and modification of graphene foams could result in a significant increase in their sorption properties and could be used for contaminated air purification in the nearest future.

Tannin foam immobilized with ferric ions for efficient removal of ciprofloxacin at low concentrations

The presence of ciprofloxacin (CIP) in natural water may cause potential threats to the environment. Adsorption is a convenient and efficient method to remove CIP from aqueous solution. Bayberry tannin (BT), a natural polyphenol, has been utilized in the synthesis of tannin foam (TF) due to its abundant polyphenolic hydroxyls to chelate with metal ions. The obtained TF was subsequently immobilized with Fe3+ via a facile chelative adsorption to fabricate functional tannin foam (TF-Fe), which was highly porous, with a porosity of 78.93%. The Fe species in the TF-Fe featured good dispersity, which were active for chelative adsorption of CIP. The adsorption of CIP on the TF-Fe was a pH-dependent process. At the optimized pH of 7.0, the TF-Fe provided the adsorption capacity of 91.8 mg g−1. When applied in removal of CIP at the low concentration of 2.0 µg mL−1, a high removal efficiency of 96.60% was still obtained, which was superior to commercial activated carbon (28.78%). The adsorption kinetics were well fitted by the pseudo-second-order rate model while the adsorption isotherms were well described by the Langmuir model. The TF-Fe was capable of recycling, which still maintained a high removal efficiency of 92.25% in the 5th cycle.

Synthesis and characterization of renewable polyurethane foams using different biobased polyols from olive oil

The overall purpose of this study was to synthesize biobased polyols to replace conventional fossil-based polyols in polyurethane foams (PUF) in a multistep approach based on green chemistry, in order to bring both improved properties and sustainability. Oleochemistry has been largely used for PUFs elaboration, but for as far as we know the use of olive oil to obtain such systems had never been reported. The synthesis of the biobased polyols is based on robust approach based on the epoxidation of the double bonds from olive oil using hydrogen peroxide, followed by the ring opening of the epoxides with acetic acid or ethanol to yield polyols with different chemical structures. The chemical structures were determined and checked by NMR and FTIR. The molar masses, the thermal stability and the viscosity were also evaluated. These biobased polyols were further tested making biobased and flexible PUF (FPUFs), with open cells. In this respect, a conventional and fossil-based polyol was partially replaced by up to 35% of each synthesized biobased polyol, alone or mixed. The structural, morphological, mechanical and thermal properties of the PFUFs obtained from the mixture of the biobased polyols were superior to the ones obtained using a sole biobased polyol. Surprisingly, these biobased foams present higher properties than the conventional and fully fossil-based PUF.

Composites of Open-Cell Viscoelastic Foams with Blackcurrant Pomace.

Taking into account the circular economy guidelines and results of life cycle analyses of various materials, it was proposed to use a blackcurrant pomace filler in the production process of viscoelastic polyurethane (PUR) foams intended for application as mattresses, pillows, or elements for orthopedics. Open-cell viscoelastic PUR foams containing 10–60 per hundred polyols (php) blackcurrant pomace were prepared. It was found that after introducing the filler to the PUR foam formulation, the speed of the first stage of the foaming process significantly decreases, the maximum temperature achieved during the synthesis drops (by 30 °C for the foam containing 40 php of filler compared to unfilled foam), and the maximum pressure achieved during the synthesis of foam containing 20 php is reduced by approximately 57% compared to the foam without filler. The growth time of the foams increases with increasing the amount of introduced filler; for the foam containing 60 php, the time is extended even by about 24%. The effect of the filler on the physical, morphological, mechanical, and functional performances of PUR foam composites has been analyzed. The use of 60 php as the filler reduced the hardness of the foams by approximately 30% and increased their comfort factor from 3 to 5.

Synthesis and characterization of flame-retardant rigid polyurethane foams derived from gutter oil biodiesel

In this study, gutter oil biodiesel-based polyols (GOBP) and a reactive-type flame retardant named diethyl bis(2-hydroxyethyl)-aminomethylphosphonate (BHAPE) were both synthesized. Subsequently, gutter oil biodiesel-based flame-retardant rigid polyurethane foams (BPUFs) were prepared with GOBP, BHAPE, aluminum hydroxide (an additive-type flame retardant) and polymeric diphenylmethane diisocyanate. The properties of the BPUFs, including density, thermal conductivity, compressive properties, chemical component, morphology, thermal stability, limiting oxygen index, cone calorimetry testing, char residues stability were characterized. Among them, BPUF-AB owning 6.97 wt% of GOBP, 18.59 wt% of BHAPE and 39.77 wt% of aluminum hydroxide obtained a lower density of 0.097 g/cm3, a lower thermal conduction of 0.048 W/(m * k) and the highest compressive strength of 187 ± 13 kPa. Fire testing revealed a highest limiting oxygen index value of 30.1% and passed the UL-94 standard test. Cone calorimetry testing revealed that the peak heat release rate and peak smoke production release of BPUF-AB were reduced by 51.08% and 57.10%, respectively. Meanwhile, the total heat release rate and total smoke production were respectively decreased by 36.88% and 40.79%. The results indicate that BPUFs derived from gutter oil biodiesel are prosperously potential biomaterials with good thermal stability for fire insulation porous materials in future architecture applications.

Open-cell polyurethane foams of very low density modified with various palm oil-based bio-polyols in accordance with cleaner production

Abstract Commercially available polyurethane foams are produced mainly from raw materials of petrochemical origin. Vegetable oils have the potential to be inexpensive and widely available resources for the synthesis of polyol compounds. The research presented here describes use of renewable and waste materials for synthesis of open-cell polyurethane foams. This paper discusses the results of studies on the influence of the palm oil’s origin on the properties of bio-polyols. Three oil versions have been chosen: refined, unrefined, as well as used cooking palm oil. A two-stage method based on epoxidation and oxirane ring opening was used to synthesize bio-polyols and these were characterized by hydroxyl values from 150 to 156 mgKOH/g. The open-cell polyurethane foam was synthesized and modified by replacing 20 wt% of petrochemical polyol with bio-polyols synthesized from palm oil. It was found that the modified polyurethane foams comply with requirements for commercial products. The modified foams were characterized by thermal conductivity ranging from 39 to 42 mW/m·K, and apparent densities between ca. 13 and 15 kg/m3. What is more, addition of bio-polyol from unrefined oil and used cooking oil had a beneficial effect on the mechanical strength of the resulting foams. The foams were characterized by more than 95% open-cell content.

A novel catalytic two-step process for the preparation of rigid polyurethane foams: synthesis, mechanism and computational studies

Synthesis of polyurethane foams catalyzed by sodium chloride both in prepolymer preparation and elongation step. The reaction mechanism involves the role of a proton shuttle between two terminal OH groups of PEG 400.

Synthesis and Preparation of Hydrophobic CNTs-Coated Melamine Formaldehyde Foam by Green and Simple Method for Efficient Oil/Water Separation

Hydrophobic porous polymeric materials have attracted great interests recently as potential candicate for oil-water separation due to their high selectivity and sorption capacity. Herein, we present a green, simple and cost-effective method to change hydrophilic melamine formaldehyde (MF) foam to hydrophobic carbon nanotubes (CNTs) coated MF foam through an immersion process. The MF foam was produced from the MF resin which was synthesized in a laboratory by a condensation reaction between melamine and formaldehyde under alkaline condition with a molar ratio of melamine to formaldehyde of 1:3. The MF foam has an open-cell structure with the average pore diameter of 350 m, density of 25 kg •m-3 and porosity of 98 %. The as-prepared CNTs-coated MF foam exhibits high sorption capacity (23–-66 g/g) for oils and organic solvents, good recyclability and high selectivity.

Composites of Semi-Rigid Polyurethane Foams with Keratin Fibers Derived from Poultry Feathers and Flame Retardant Additives.

Semi-rigid composites of polyurethane foams (SRPUF) modified with the addition of keratin flour from poultry feathers and flame retardant additives were manufactured. Ten percent by mass of keratin fibers was added to the foams as well as halogen-free flame retardant additives such as Fyrol PNX, expandable graphite, metal oxides, in amounts such that their total mass did not exceed 15%. Thermal and mechanical properties were tested. Water absorption, dimensional stability, apparent density and flammability of produced foams were determined. It was found that the use of keratin fibers and flame retardant additives changes the foam synthesis process, changes their structure and properties as well as their combustion process. The addition of the filler made of keratin fibers significantly limits the amount of smoke generated during foam burning. The most favorable reduction of heat and smoke release rate was observed for foams with the addition of 10% keratin fibers and 10% expandable graphite. Systems of reducing combustibility of polyurethane foams using keratin fillers are a new solution on a global scale.

Potential use of black liquor as lignin source for synthesis of polyurethane foam

This study was conducted to recover lignin from black liquor for synthesis of lignin-based polyurethane foam (LPUF). To do so, lignin was precipitated from black liquor through acid precipitation at different pH values. The precipitated lignin samples were characterized by mid-infrared spectroscopy (MIR), thermogravimetric analysis (TGA), proton nuclear magnetic resonance (1H-NMR), and ultraviolet–visible (UV–Vis) spectroscopy (UV–Vis) techniques. After that, lignin sample with higher purification and lower molecular weight was selected for preparation of lignin polyol. Then, microwave-assisted liquefaction was employed to liquefy lignin sample. The obtained lignin polyol was used successfully to synthesize LPUF samples in different 4, 4′-diphenylmethane diisocyanate (MDI) indexes. The effect of MDI index on properties of LPUF samples was investigated through MIR, scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and compressive strength tests. The results demonstrated that MDI content could change morphology of the prepared LPUF samples and caused reduction of cell size and more regularity of cellular structure. Also, thermal and mechanical properties of LPUF samples were found to be influenced by MDI index.

Synthesis and Modification of Polyurethane Foam Doped with Multi-walled Carbon Nanotubes for Cleaning up Spilled Oil from Water

Marine oil spills have raised widespread environmental concerns. Adsorbents with high oil absorption efficiency and reusability are highly desirable. This paper demonstrates a technical route for the manufacture of polyurethane-based adsorbents, aiming at developing robust and efficient materials for treating oil-contaminated water or remedying emergency oil spill accidents. The investigation includes the synthesis of polyurethanes modified with multi-walled carbon nanotubes, the characterizations of their properties, and the analysis of the capacity and feasibility of their applications in oil–water separation. The compositions of the products were characterized by FTIR, XPS, and Raman spectroscopy; the morphologies were analyzed by SEM; the hydrophobicities were tested by the water contact angle, and the thermal properties by TGA; the mechanical properties were depicted by Young’s modulus and the tensile-strain response performance; and the measurements of the absorption capacities and their performance in applications for oils-water separation were conducted in a self-designed apparatus and determined by gravimetric analysis. The results indicate that the developed adsorbents are superhydrophobic and highly robust with a water contact angle of 159°, tensile strain 27% higher and compressive strain 35% lower than regular polyurethanes, absorption capacity up to 60 g g−1, and reusability of 900 absorption–desorption cycles. The high oil absorption efficiency, capacity, and reusability of the adsorbents were confirmed by various oil/organics-water systems, such as engine oil-, silicone oil-, chloroform-, hexane-, toluene-, and kerosene-water system. It is concluded that the adsorbents are efficient not only for floating oils/organics-water but also for well dispersed or mixed oils/organics-water systems; and they can be operated in not only a batch mode for high absorption–desorption cycles but also in a continuous mode for a long operational period, which exhibits great potential and is of particular interest for the adsorbents to be used in large scale oil/organics spill cleanups.

Polyol and polyurethane foam from cellulose hydrolysate

AbstractBACKGROUNDAt present the majority of polyurethanes, including polyurethane foams (PUF), are obtained from petrochemical substrates. However, green chemistry policy worldwide and restricted crude oil resources are driving the use of biological substrates to make polyurethanes. Widely available cellulose seems to meet the expectation of a polyol substrate for use in synthesizing polyurethane foams provided that it is converted first into liquid resin with free hydroxyl groups.RESULTSCellulose hydrolysate was functionalized with glycidol and ethylene carbonate to obtain polyol. The product was characterized by infrared and proton nuclear magnetic resonance spectroscopy and matrix‐assisted laser desorption ionization–time‐of‐flight spectrometry. The polyol then was used to obtain rigid polyurethane foam. The foam was characterized by physicochemical methods to determine apparent density, water uptake and polymerization shrinkage.CONCLUSIONSNew polyol was obtained from cellulose hydrolysate by reaction with glycidol and ethylene carbonate in the presence of potassium carbonate as catalyst without solvent. This polyol contains hydroxyalkylated cellulose units incorporated into its structure and is suitable for synthesis of polyurethane foams. The properties of the foam were close to those of typical rigid polyuerethane foams used in industry. The foam showed good thermal resistance. Thermal exposure of obtained foam results in increase of compression strength. © 2020 Society of Chemical Industry (SCI)

Recovery of Residues from Olive Industry: Characterization of Simple and Acetylated Lignin

Lignin is a renewable material obtained in large quantities as a by-product of the olive industry. In this context, this study aims to examine lignin as macro-monomers in the synthesis of rigid polyurethane foam after chemical modification. Indeed, the lignin extracted from the olive residue is used by chemical treatment according to the organosolv process. Comparison by characterization of the single isolated lignin and the acetylated lignin according to the physicochemical analysisTGA, DSC, FTIR, C-13 NMR, 1-H NMR, and molar mass distribution (sec) shows its value as biomass capable of being transformed into polyol afterchemical modification. acetylation increases the weight and the number of molar masses by 25-50% was also determined. Acetylation has a greater effect on the short chains which are probably richer in free phenolic groups. Mass distribution analyzes reveal a relatively high molar mass in organosolv lignin moreover, polydispersity values are very high (20 &gt;&gt; 1). The characterization of spent olive cake reflects the interest of using this biomass as a source of renewable energy for the production of industrial polymers.

Ni mesostructured catalysts obtained from rice husk ashes by microwave-assisted synthesis for CO2 methanation

Abstract In this work, rice husk ashes were used to obtain a high purity silica precursor to synthesize mesoporous silica frameworks. A novel route for the synthesis of mesocellular silica foam (MCF) was developed using microwave irradiation during the hydrothermal treatment. Cyclohexane and cetyltrimethylammonium bromide were employed as swelling and structure-directing agents, respectively. Ni-based catalysts supported on MCM-41 and MCF mesostructured materials were obtained using two methods, one-pot and incipient wetness impregnation. The catalysts prepared for both methods presented noticeable differences in the metal-support interaction, which were observed by TEM, SAXRD, TPR and XPS. The impregnated catalysts showed preferentially Ni particles inside the pore structure of the support while the one-pot catalysts also showed Ni particles within the silica framework. The catalysts were evaluated in the CO2 methanation reaction between 200 and 500 °C at atmospheric pressure. The samples prepared by impregnation showed better catalytic performance than those prepared by the one-pot method. Thereby, the Ni particles highly distributed within the pore improved the CO2 methanation reaction. The Ni/MCF_ch_iwi presented the best catalytic performance reaching CO2 conversions and CH4 selectivities close to the reaction equilibrium, from 350 to 500 °C. The Ni/MCF_ch_iwi also showed high structure and catalytic stability, as well as coke resistance formation under reaction conditions.

Synthesis and Characterization of Graphite Composite Foams for Oil Spill Recovery Application

The aim of this paper is the synthesis and characterization of a composite silicone foam filled with expanded graphite (EG) for oil spill recovery applications. The EG foams were obtained using a foaming slurry consisting of a mixture of siloxane compounds as the matrix with an EG filler. The effect of the filler content’s performance on an innovative composite silicone-based foam was investigated. All the obtained samples exhibited an open cell morphology. Each foam was evaluated in four commonly used oils (kerosene, pump oil, naphtha and crude oil). Additionally, kinetics was studied in order to investigate the physical, chemical and mass transport mechanisms that act during the absorption phenomenon and uptake evolution of the contaminants. Foam filled with 3% of EG exhibited the highest absorption capacity, particularly with light oils kerosene and virgin naphtha (854 and 1016 wt.%, respectively). Furthermore, the kinetic study showed that pseudo-second order mechanisms better fitted the composite absorption performances, suggesting that the oil sorption into EG filled polydimethylsiloxane (PDMS) foams could be related to chemisorption mechanism. The results evidenced a good oil sorption capability and water/oil selectivity indicating this class of materials as a potentially applicable material for oil spill remediation.

Glass bubble reinforced polyurethane foams with high mechanical strength for cryogenic temperature insulation

AbstractIn this study, glass bubble (GB) is added to polyurethane (PU) foams at different weight ratios—0, 0.25, 0.5, 0.75, and 1 wt% —to investigate the changes in the mechanical and thermal properties of the foam. By conducting several tests and measurements, the density, cell morphology, compressive strength, and thermal conductivity of the foam are studied. In particular, the effect of GB additives is examined by conducting compression tests at various temperatures (−163, −100, −40, and 20°C). Scanning electron microscopy and X‐ray microscope reveal that the foams exhibit higher stability below 0.5 wt%, which improves the thermal performance. On the other hand, the compressive strength of the foams increases for all weight ratios of GB, and it increases sharply at 0.75 wt%. In addition, the chemical interactions and the dispersion of additives in the PU matrix are investigated through Fourier transform infrared and X‐ray diffractions analysis. It is found that the synthesis of PU foams with GB nanoparticles is an efficient method for improving the mechanical properties and insulation performance of the foam for LNG insulation technology.

Synthesis of Carbon Foam Using Xanthan-Gum Additive and Characterization for its Heat Absorbing and Retarding Properties

In this work a facile synthesis method is adopted to demonstrate the large mesoporous carbon foam. The green foam was made from fine flour, yeast and xanthan gum were used as a base, leaving agent and binding agent respectively. After the blowing process the foam is placed in a tube furnace for pyrolysis. Finally, the foam heat absorption properties as well as heat retarding properties were established in contrast to traditional aluminum-based heat sink as well as K23 (aluminosilicate refractory) brick.