Synthesis Of Foams Research Articles

Interface-Initiated Polymerization Enables One-Pot Synthesis of Hydrophilic and Oleophobic Foams through Emulsion Templating.

Unlike oil-absorbing hydrophobic and oleophilic materials, porous materials that simultaneously display hydrophilicity and oleophobicity in air are rare, but they are unique in selectively removing water from bulk oil. Preparation of such porous materials is limited to the surface coating of raw porous materials, which faces problems such as pore clogging and uneven coating on inner surfaces. Herein, a one-pot approach to fabricating hydrophilic and oleophobic foams from oil-in-water high internal phase emulsions through a facile interface-initiated polymerization strategy is reported. The foams have interconnected macroporous structure. They can absorb water drops quickly while repelling oils in air. Such foams may find applications not only in oil-water separation (e.g., fuel purification), but also for efficient removal of contaminants (e.g., dyes) from oil-containing wastewater, where the oleophobicity helps foams to eliminate the oil fouling issue.

Synthesis of Polyurethane Foam Considering Mixture Blowing Agents for Application to Cryogenic Environments

AbstractPolyurethane foams, which are among the most widely used insulating materials, are generally fabricated by the chemical reaction between isocyanate and polyol‐containing chemical additives and blowing agents. Recently, many kinds of blowing agents have been used for the fabrication process of polyurethane foam, such as hydrochlorofluorocarbons (HCFCs) and chlorofluorocarbons (CFCs). However, issues have continuously arisen regarding the destruction of the ozone layer due to these compounds. In the present study, polyurethane foams are manufactured using a mixture of water blowing agents and hydrofluorocarbons (HFC‐365mfc). These samples are subjected to mechanical tests to investigate the effects of the blowing agents on the mechanical properties of the polyurethane foam within a temperature range of 25 to −163 °C. In addition, thermal and microstructural investigations are conducted depending on the content of the HFC‐365mfc. From the scanning electron microscopy observations, the sizes of the structure cells and the windows are found to decrease with the increase in HFC‐365mfc content. In addition, from the Fourier transform‐infrared spectroscopy observations, the chemical bonds that affect mechanical performance are found to be more distributed with the increase in HFC‐365mfc content.

Synthesis of biocompatible TiZr-based bulk metallic glass foams for bio-implant application

Abstract A series of porous toxic-element-free TiZr-based bulk metallic glass foams (BMGFs) with porosities ranging from 2.0% to 38.9% were fabricated by hot-pressing method. The results indicated that the BMGFs with pore sizes of 100–300 μm exhibit relatively good mechanical properties, Young’s moduli ranging from 5.8 to 56.4 GPa and compressive strength from 33 to 979 MPa which well match the properties of human bone. In in vitro tests, the TiZr-based BMGFs with porosities of 12.7% and 34.8% showed non-cytotoxicity and high extracellular calcium deposition. Owing to the excellent combination of suitable porosities, consistent mechanical properties, and high biocompatibility, the TiZr-based BMGFs are promising candidates for use in bio-implant applications from the viewpoints of avoiding stress shielding and bio-unfriendly symptoms in the human body.

Metal-free nitrogen-rich carbon foam derived from amino acids for the oxygen reduction reaction

The following paper presents the synthesis of nitrogen-rich carbon foams (N-CFO) from amino acids through their thermal decomposition in the presence of solid and removable nanoparticles (template). N-CFO were synthesized by carbonizing l-lysine as the carbon phase precursor and using a hard template of CaCO3 (added as nano-sized powder). The carbonization process was carried out in a temperature range of 700–900 °C, under the flow of nitrogen. The results show that the textural and chemical properties among other nitrogen content of the N-CFO can be controlled by manipulating carbonization temperature. The obtained N-CFO were either micro- or mesoporous matrixes (open porosity) with high nitrogen content in the range from 4.1 to 12.4 wt%. The walls of the produced N-CFO had a thickness up to 10 nm. The metal-free catalysts such as N-rich carbon foams are valuable materials in oxygen reduction reaction, which is a key reaction for metal–air batteries. It was found that a four-electron reduction process is predominant.

Synthesis of new mesostructured cellular foams (MCFs) with NaY zeolite and their application to sorption of thorium ions

Abstract The paper presents the new way of preparation of MCF foams with NaY zeolite. Significant changes in the amount of micro and mesopores in relation to the amount of NaY zeolite and 1,3,5-trimethylbenzene (TMB) added during the synthesis was observed. It suggests the possibility of controlling the micro/mesopores ratio by applying the proposed method. Environmental aspects of using new MCF/NaY foams is related to the adsorption of thorium ions (Th+4). The term of “MCF/NaY materials” refers to the general name of the material without referring to the content and state of zeolite. The obtained materials were highly effective in relation to Th+4. The adsorption capacity was greater when the number of micropores was lower. The dependence of adsorption capacity of Th+4 ions on aluminum atoms content was also confirmed.

Sound Absorption Coefficient and Water Content Responses in Acoustic Analysis Based on Renewable Polyurethane Foam Composites

In physiological health, negative effects are felt when unwanted noise is present. Given the negative effects of the unwanted noise, it become important to examine how environmentally-friendly and efficient sound absorbing materials could be developed. Some of the materials associated with acoustic absorption properties entail polymer foams. Particularly, the foams aid in controlling noise. The central purpose of this study was to examine renewable polymer (PU) foam composites’ aspects of moisture content and acoustical properties. Four major parameters that were evaluated included the thickness of the sample, the type of filler, the ratio of the fillers, and the nature of the monomer. A design of experiment (DoE) technique was employed. To prepare the PUs foams, 28 mm and 100 mm were selected as diameters for the cylindrical shapes on focus. Plotting the main effects was achieved through ANOVA, upon which variations in the role and performance of the selected input factors were discerned. From the findings, it was established that when bio-epoxy (B) was used in conjunction with renewable PU foams, the moisture content was greater than the case involving petroleum based PU foam synthesis. Hence, renewable PU foam composite is seen to be realized at 0.9, especially if the filler ratios and size are increased; with the experimental conditions set at 3 kHz. Overall, the study established that the renewable Pus’ state of sound absorption exhibits good agreement with the case of synthetic PU foam.

Curcumin as a natural compound in the synthesis of rigid polyurethane foams with enhanced mechanical, antibacterial and anti-ageing properties

Abstract This paper presents the effect of natural compound (E,E)-1,7-bis(4-Hydroxy-3-methoxyphenyl)-1,6-heptadiene-3,5-dione (curcumin) on the antibacterial, anti-aging, mechanical and morphological properties of polyurethane (PU) rigid foams. Concentrations of 1 wt%, 2 wt% and 5 wt% of antibacterial compound was used, and the infection reduction capacity was evaluated for different types of bacteria (Escherichia coli (G-) and Staphylococcus aureus (G+). In order to determine all assumed properties the synthesized PU foams were characterized by analytical (Fourier Transform Infrared Spectroscopy, FTR), morphological (Scanning Electron Microscopy, SEM), bactericidal effects (Disc Diffusion Method), thermal characteristic (Thermogravimetric Analysis, TGA), mechanical techniques (three-point bending test and compressive test) and physical properties (apparent density, dimensional stability, contact angle, water uptake, color characteristics). Compared to the reference foam, compositions modified with 1 and 2 wt% of the curcumin showed greater compressive strength (increase of 10 and 7%, respectively), higher flexural strength (increase of 17 and 7%, respectively), less water uptake (decrease by 12 and 10%, respectively), as well as, better thermal properties. On the other hand, it has been shown, that in all cases, curcumin can be used as a natural anti-ageing additive for polymers. The addition of curcumin in the amount of 1, 2 and 5 wt% considerably improved the stabilization of the polymer. Moreover, based on the microbiological results, it has been shown that the addition of 5 wt% of the extract is suitable for the manufacturing of PU foams with enhanced antibacterial properties.

Attempts to Upcycle PET Wastes into Bio-based Long-lasting Insulating Materials

Following the green chemistry principles, three series of polyols with tailored chemical structures were obtained from PET wastes degradation via glycolysis and/or aminolysis and subsequent esterification-transesterification and/or amidation reactions, using an organic catalyst. As cleaving agents there were used various mixtures of renewable or potentially renewable reagents, selected from those that can be obtained from biomass by already applied or investigated and eventually patented biochemical and/or chemical processes. The polyols were characterized by physical-chemical methods, 1H-NMR, 13C-NMR and FT-IR Spectroscopy, and tested in the synthesis of rigid polyurethane foams, showing appropriate properties for spray foams formation and leading to materials with properties similar to conventional spray foams.

Synthesis and characterization of 3D-printable geopolymeric foams for thermally efficient building envelope materials

Synthesis and characterization of 3D-printable foamed fly ash-based geopolymer matrices for thermal insulation is the focus of this paper. A surfactant-based foaming process, multi-step mixing that ensures foam jamming transition and thus a dry foam, and microstructural packing to ensure adequate skeletal density are implemented to develop foamed suspensions amenable to 3D-printing. The foamed suspensions show lower yield stress with increasing surfactant contents, especially above the foam jamming transition. The mixtures demonstrate adequate extrudability, shape retention, and buildability. The geopolymeric foams show porosities ranging from 55 to 75% and bulk densities from 0.6 to 1.0 g/cm3, and these properties are similar irrespective of whether the mixtures are extruded or conventionally cast. The thermal conductivities of the foamed matrices range from 0.15 to 0.25 W/m-K. It is shown that designed architectures that minimize heat transfer can be printed using foamed matrices to obtain sandwich wall panels with thermal insulation properties comparable to or better than those of currently available insulated concrete wall panels. This positions 3D-printing as a strategy to develop composite systems with previously unattainable thermal performance.

Synthesis and Acoustic Study of a New Tung Oil-Based Polyurethane Composite Foam with the Addition of Miscanthus Lutarioriparius.

Polyurethane foam is commonly used in the automobile industry due to its favorable acoustic performances. In this study, a new tung oil-based polyurethane composite foam (TOPUF) was prepared by a one-step method. Different forms and contents of miscanthus lutarioriparius (ML) were used in TOPUF for improving acoustic performance. Polyurethane foams were characterized by means of Fourier transform infrared and SEM. The acoustic properties and mechanical properties of TOPUF, obtained with ML, were determined and compared with pure petroleum-based polyurethane foam. The results illustrate that the modification of TOPUF with the ML has a positive effect on the acoustic and mechanical properties in comparison to the unmodified foam. TOPUF obtained with ML powders has better acoustic performance than that obtained with ML strips. The optimum acoustic performance is achieved at the filler content of 0.3 wt%. The average sound absorption coefficient and transmission loss can reach 0.518, and 19.05 dB, respectively.

Synthesis of fish skin-derived 3D carbon foams with broadened bandwidth and excellent electromagnetic wave absorption performance

The novel three-dimensional (3D) co-doped carbon foam was fabricated via a facile hydrothermal and subsequent pyrolysis process using fish skin as carbon precursor. The fish-derived carbon foam (CFs) obtained at 650 °C (CFs-650) possesses large specific surface area of 1369.3 m2/g with natural inherited micropore-dominate porosity. Moreover, the heteroatoms O and N in the fish skin are uniformly planted into the carbon frameworks, which is highly advantageous for the attenuation of microwave energy. The unique architecture endows the 3D carbon foam with impressive microwave absorbing property. Especially, the broadest bandwidth (RL < −10 dB) of CFs-650 can be up to 8.6 GHz (9.4–18 GHz) at 3 mm with the minimum reflection loss (RL) of −33.5 dB. The optimal RL of CFs-650 is −52.6 dB at 15.8 GHz with the matching thickness of 2.6 mm. The mechanism of the microwave absorption of the carbon foam is attributed to electric conductive loss, interfacial polarization relaxation, multiple reflections and scattering. The low-cost and eco-friendly carbon foam has great potential for application of microwave absorption.

Liquefaction of Peanut Shells with Cation Exchange Resin and Sulfuric Acid as Dual Catalyst for the Subsequent Synthesis of Rigid Polyurethane Foam

The conversion of lignocellulosic biomass from renewable raw materials to high value-added fine chemicals expanded their application in biodegradable polymers materials synthesis, such as polyurethanes and phenolic resin, etc. In this work, the strong-acid cation exchange resin and sulfuric acid as the dual catalyst offered an effective way to catalyze the liquefaction reaction of the peanut shells. The properties of liquefied products were characterized by means of hydroxyl value, viscosity and solubility tests, while the properties of peanut shells and liquefaction residue were analyzed by means of ATR-FTIR, TG and SEM techniques. The results indicated that the liquefied products could be completely dissolved in deionized water, methanol and polyethylene glycol, respectively, and they could be a preferable substitution of petrochemical polyols as soft segments to synthesize the rigid polyurethane foams. Moreover, the cellulose and hemicellulose in the peanut shells were easily decomposed into smaller molecules via the breakage of the C–O bond besides five-membered and hexatomic ring, while the lignin could be degraded via the breakage of the C–O chemical bonds of β-O-4, 4-O-5 and dibenzodioxocin units. The fabricated rigid polyurethane (RPU) foam, containing higher percentage of open pores with uniform size, can be potentially utilized for flower mud and sound-absorbing materials.

Chemical structures, rheological and physical properties of biopolyols prepared via solvothermal liquefaction of Enteromorpha and Zostera marina biomass

In this work, liquefied biomass from the Baltic Sea was used for the preparation of rigid polyurethane (PUR) foams. The biomass contained 10 wt% of Enteromorpha macroalgae and 90 wt% of Zostera marina seagrass characterized by a high content of cellulose. The influence of time, temperature and the type of solvent on the efficiency of the liquefaction process and properties of biopolyols was determined. Obtained materials were analyzed in terms of chemical structure, rheological properties, thermal stability and basic physical and mechanical properties. It was found that optimal parameters for liquefaction of used biomass were: temperature of 150 °C, reaction time of 6 h and a solvent mixture containing glycerol and poly(ethylene glycol) in ratio of 50:50 (biopolyol 50G50P_150). Under these conditions, 78 wt% of biomass was liquefied and resulting biopolyol was characterized by a hydroxyl number of 650 mg KOH/g. Depending on the used solvent mixture and the liquefaction temperature, biopolyols showed the character of Newtonian or non-Newtonian liquids. Rigid PUR foams were obtained by substitution of petrochemical polyol with 10, 20 and 30 wt% of biopolyol. It was found that the addition of biopolyol to foams’ formulations did not cause significant changes in their chemical structure, while mechanical strength and thermal stability were enhanced. The presented study confirms that biomass from the Baltic Sea can be used for the synthesis of biopolyols and rigid polyurethane foams.

Development of Copolyamide-66/6 Cross-Linked Foams by a One-Step Reactive Extrusion Process

The simultaneous chemical cross-linking and foaming of aliphatic copolyamide by one-step reactive extrusion using a bifunctional trialkoxysilaneimidazoline additive is studied. The aim was to reach efficient melt strength enhancing the cell growth without coalescence. From liquid NMR analyses, the cross-linked foam synthesis was evidenced resulting from both imidazoline ring opening (further reacting with the polyamide carboxylic acid end-groups) and alkoxysilane hydrolysis–condensation reactions (leading to cross-linking reaction and ethanol formation). From these chemical modifications, ethanol concomitantly released lead to the expansion of the cross-linked copolyamide. From the knowledge of this chemical mechanism, various extruder and formulation parameters have been modified and their impact scrutinized to optimize the foam morphology. With our optimized conditions, it was possible to synthesize rigid foam with mean pore size mainly below 90 μm and a density around 0.36 kg·m–3 while reaching reasona...

Synthesis of open-cell copper foam using friction sintering

A technique for doing solid-state sintering on friction stir welding or milling machines is developed. Heat and pressure needed for sintering are generated using a rotating tool with a flat shoulder. The developed process results in fast heating and cooling rates, sharply reducing sintering time. Sintered parts can be extracted within minutes from end of sintering. The process is cost-effective and can be used to produce large, three-dimensional sintered parts. The technique is used to fabricate open-cell copper foam using sintering and dissolution process with NaCl particles as space holders. Microstructural features of fabricated foam are studied using scanning electron microscopy, microcomputed tomography, and optical microscopy. Its mechanical properties are studied using compression tests. Plateau stress, compressive strength, energy absorption density, and thermal conductivity of obtained foam are on par with those reported in literature for foams obtained using furnace sintering and friction compaction methods. The developed foam has three-scale microstructure and could be used in heat exchanger, sound absorption, catalysis, boiling, and filtration applications.

Synthesis and Characterization of Bio-Based Rigid Polyurethane Foams with Varying Amount of Blowing Agent

We report on the rigid polyurethane foam (RPUF) with varying amount of blowing agent. The effects of blowing agent in the formation of polyurethane will be characterized using scanning electron microscopy (SEM) and fourier transform infrared (FTIR) spectroscopy. SEM images revealed that varying the amount of blowing agent will significantly change the surface morphology of the resulting RPUF. The average cell size of the RPUF increases with increasing amount of blowing agent. Moreover, FTIR results revealed the presence of functional group related to formation of urethane bonds such as N-H, C=O, C=N and C-O-C stretching suggesting that polyurethane foam was successfully synthesized. This simple and straightforward process of RPUF using water as blowing agent will be economical.

Synthesis of biomass tar-derived foams through spontaneous foaming for ultra-efficient herbicide removal from aqueous solution

Pyrolysis is one of the most important approaches to convert waste biomass into renewable energy and biomaterials, and the tar is the inevitable by-product of this process. In this study, carbon foams were prepared innovatively with biomass tar as the precursor through spontaneous gas foaming approach and used for dicamba removal from aqueous solution. The results showed that prepared carbon foams had unique properties including rich microporous structure and high specific surface area (reaching 1667 m2/g). In addition, the prepared carbons had high thermal stability due to the high graphitic degree. The adsorption results indicated that pH showed a great effect on the adsorption of dicamba onto the prepared carbon foams. The carbon foam exhibited ultra-fast dicamba removal and ultra-high adsorption capacity of 891.74 mg/g at room temperature. The adsorption process was well described by pseudo-second-order kinetics and Langmuir isotherm models. The thermodynamic study indicated dicamba adsorption onto the prepared carbon foams was a spontaneous and exothermic process. In addition, the good reusability from recovery test demonstrated that the prepared carbon foams had promising potential for dicamba removal from aqueous solution.

Enhancement of Mechanical and Thermal Characteristics of Polyurethane-Based Composite with Silica Aerogel

Synthesis of polyurethane foams (PUF) with silica aerogel nanoparticles is an efficient alternative to improve the mechanical and thermal properties of the foam owing to the outstanding thermal insulation properties of porous silica aerogel nanoparticles. Silica aerogel was added into polyurethane foams at different weight percent (0, 1, 3, 5 wt.%) to observe the changes in the material properties. To confirm the applicability of the synthesized PUF to the heat insulating material, compressive tests were carried out at ambient and cryogenic temperature (20, -163°C) and the thermal conductivities were measured according to wt.%. In addition, the cell microstructure was identified using FE-SEM to analyze the effect of silica aerogels on the foam morphologies. As a result of the experiment, it was confirmed that the mechanical strength and the heat insulation performance were improved in the polyurethane foam containing 1 wt.% of silica aerogel.

Synthesis of aminophosphonate polyols and polyurethane foams with improved fire retardant properties

ABSTRACTAminophosphonated polyols with flame retardant properties are synthesized by ring opening polymerization using diethyl‐N,N‐bis(2‐hydroxyethyl) aminomethyl phosphonate (Fyrol‐6) as initiator. The influence of the catalyst type and its concentration on the polymerization rate are studied. The catalyst system formed by potassium methoxide (MeOK) in DMSO as a solvent presents the highest polymerization rate and allows reducing the polydispersity. The thermal resistance of the synthesized polyols is confirmed by the char residues formation. Finally, PU foams are synthesized containing up to a 50 pph of PFyCs[1:1], preserving good cellular structure up to a 25 pph content and improving the fire resistance by increasing the char residue from 7.79 to 22.13 wt % and decreasing the PHRR and the smoke production according to TGA and cone calorimeter tests, respectively. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47780.

Novel Biobased Polyol Using Corn Oil for Highly Flame-Retardant Polyurethane Foams

A novel bio-based polyol was synthesized using corn oil and 2-mercaptoethanol via thiol-ene reaction as an alternative to petroleum-based polyol for the synthesis of polyurethane foams. The polyol was analyzed using wet chemical techniques to obtain hydroxyl number and viscosity. Infrared spectroscopy and gel permeation chromatography were used to confirm the structural properties of the foams. Flame-retardant polyurethane foams were prepared by the addition of different concentrations of dimethyl methyl phosphonate (DMMP) in final foam composition. The effect of DMMP on the thermo-mechanical properties of the polyurethane foams was analyzed. The TGA analysis showed improved stability of the final char with addition of DMMP in the foams. All the foams maintained a well-defined cellular structure and over 95% of closed cell content. The horizontal burning test showed reduced burning time and weight loss from 115 s and 38 wt.% for the neat foams, to 3.5 s and 5.5 wt.% for DMMP-containing foams (1.94 wt.% P). The combustion test using cone calorimeter showed a considerable reduction in heat release rate and total heat release. Thus, our study shows that corn-oil based polyol can be used to produce renewable polyol for industrially producible rigid polyurethane foams. The addition of a small amount of DMMP could result in a significant reduction in the flame-retardant properties of the polyurethane foams.