Direct silanization of polyurethane foams for efficient selective absorption of oil from water

Absorption is an effective method to collect oil spills and solvent leakages from water. However, the currently used oil absorbents are still suffering from high cost, tedious preparation, and low recyclability. In this work, we report an extremely simple and low‐cost strategy to produce oil absorbents by directly coupling alkoxysilane onto the surface of polyurethane (PU) foams. Such direct silanization renders the initially amphiphilic foams a strong hydrophobicity and consequently a water‐repelling and oil‐absorptive functionality. The silanized foams exhibit highest absorption capacities as well as best recyclability among all PU‐based oil absorbents. More practically, the silanized PU foams can be used to recover crude oil spills with an absorption capacity of higher than 75 times of their own weight, and maintain 90% of the initial absorption capacity after eight times reusage. Interestingly, we invent portable oil suckers for continuous oil absorption from water by filling vacuum cleaners with the silanized foams. © 2017 American Institute of Chemical Engineers AIChE J, 63: 2232–2240, 2017     

Synthesis and performance of different polyurethane foams as oil sorbents

Oil sorption (g g^?1) through different polyurethane foams has been investigated in this study. Polyurethane foams were synthesized with different additives: glycerol, propylene glycol, polyethylene glycol 400, and 1‐dodecanol. All foams were applied as sorbents of diesel, motor oil, gasoline, kerosene, and crude oil. The foams were characterized using Fourier transform infrared spectroscopy, thermogravimetry and differential scanning calorimetry, compressive resistance at 10% deformation and the elastic modulus, scanning electron microscopy, and apparent density. The best performance of oil sorption was achieved with PUF‐3, which has the greatest amount of the chain extender polyethylene glycol 400 and lowest density of all the evaluated foams. The sorption capacities (g g^?1) of PUF‐3 were 16.8 (diesel), 15.7 (gasoline), 20.7 (oil motor), 25.4 (kerosene), and 29.8 (crude oil) and 100% removal of diesel from water was achieved, approximately. The foams with chain extenders and lower density values performed better as oil sorbents. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 45409.     

Polyurethane foams from soyoil‐based polyols

The focus of this work was to synthesize bio‐based polyurethane (PU) foams from soybean oil (SO). Different polyols from SO were produced as follows: soybean oil monoglyceride (SOMG), hydroxylated soybean oil (HSO), and soybean oil methanol polyol (SOMP). The SOMG was a mixture of 90.1% of monoglyceride, 1.3% of diglyceride, and 8.6% of glycerol. The effect of various variables (polyol reactivity, water content curing temperature, type of catalyst, isocyanate, and surfactant) on the foam structure and properties were analyzed. SOMG had the highest reactivity because it was the only polyol‐containing primary hydroxyl (? OH) groups in addition to a secondary ? OH group. PU foams made with SOMG and synthetic polyol contained small uniform cells, whereas the other SO polyols produced foams with a mixture of larger and less uniform cells. The type of isocyanate also had an influence on the morphology, especially on the type of cells produced. The foam structure was found to be affected by the water and catalyst content, which controlled the foam density and the cure rate of the PU polymer. We observed that the glass transition (T_g) increased with the OH value and the type of diisocyanate. Also, we found that the degree of solvent swelling (DS) decreased as T_g increased with crosslink density. These results are consistent with the Twinkling Fractal Theory of T_g. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Effect of auxiliary blowing agents on properties of rigid polyurethane foams based on liquefied products from peanut shell

The bio‐based rigid polyurethane (PU) foams were successfully prepared based on liquefied products from peanut shell with water as the blowing agent. The influence of reaction parameters on properties of rigid PU foams was investigated. Rigid PU foams showed excellent compressive strength and low shrinkage ratio, whereas their open‐cell ratio and water absorption were higher. Therefore, rigid PU foams were synthesized with petroleum ether, diethyl ether, and acetone as auxiliary blowing agents and their inner temperature, shrinkage performance, density, compressive strength, water absorption, and open‐cell ratio were determined. The results indicated that above rigid PU foams showed lower compressive strength than the original foam but their water absorption and close‐cell ratio were improved. Compared with the original foam, the highest inner temperature of rigid PU foams with petroleum ether, diethyl ether, and acetone as auxiliary blowing agents was reduced by 11, 19, and 23 °C, respectively. Typically, foams with petroleum ether as auxiliary blowing agent displayed better water absorption and swelling ratio in water and exhibited obvious improvement in close‐cell ratio. These foams were preferable for application in thermal insulation materials because of low thermal conductivity and better corrosion resistance. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45582.     

Flexible polyurethane foams synthesized employing recovered polyols from glycolysis: Physical and structural properties

Polyurethane (PU) is one of the most important polymers with a global production of 17.565 million tons, which makes its recycling an urgent task. Besides, the main goal of PU recycling is to recover constituent polyol as a valuable raw material that allows to obtain new PU with suitable properties. Split‐phase glycolysis can be considered the most interesting PU recycling process since provides high‐quality recovered products in terms of polyol purity. The aim of this work was to evaluate several recovered polyols as replacement of the raw flexible polyether polyol in the synthesis of new flexible PU foams. These recovered polyols come from the split‐phase glycolysis of different types of PU foams and employing as cleavage agents diethylene glycol or crude glycerol (biodiesel byproduct). The influence of the foam waste type and of the cleavage agent on the foams properties was analyzed. The recovered polyols were evaluated by performing several foaming tests according to the method of free expansion foaming of conventional flexible foam. Synthesized flexible foams containing different proportions of recovered polyols were characterized by means of scanning electron microscopy, density and tensile properties; obtaining similar and sometimes even better values compared to the foams manufactured from commercial polyols. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45087.     

Preparation and characterization of microencapsulated ammonium polyphosphate and its synergistic flame‐retarded polyurethane rigid foams with expandable graphite

A facile and effective method for the preparation of microencapsulated ammonium polyphosphate (MAPP) by in situ surface polymerization was introduced. The ‘polyurethane‐like’ shell structure on the surface of MAPP was characterized by using Fourier transform infrared spectroscopy. The hydrophobicity and thermal behavior of MAPP were studied by using water contact angle tests and thermogravimetric analysis. The foam density and mechanical properties of polyurethane (PU) rigid foams were investigated. The flame retardancy of PU rigid foams formulated with MAPP was evaluated by using limiting oxygen index and cone calorimetry. The results show that MAPP can greatly increase the flame retardancy of PU materials. Also, there is a synergistic effect between MAPP and expandable graphite in flame retarding PU rigid foams. Moreover, the water resistance property of PU/MAPP composites is better than that of PU/ammonium polyphosphate. The morphology and chemical structure of PU/MAPP rigid foams after burning were systematically investigated. © 2013 Society of Chemical Industry     

Interpenetrating polymer networks based on polyol modified castor oil polyurethane and poly(2‐ethoxyethyl methacrylate): Synthesis,chemical, mechanical,thermal properties,and morphology

Interpenetrating polymer networks (IPNs) of glycerol modified castor oil polyurethane (GC‐PU) and poly(2‐ethoxyethyl methacrylate) poly(2‐EOEMA) were synthesized using benzoyl peroxide as initiator and ethylene glycol dimethacrylate (EGDM) as crosslinker. GC‐PU/poly (2‐EOEMA) interpenetrating polymer networks were obtained by transfer molding. The novel GC‐PU/poly (2‐EOEMA) IPNs are found to be tough films. These IPNs are characterized in terms of their resistance to chemical reagents thermal behavior (DSC, TGA) and mechanical behavior, including tensile strength, Young's modulus, shore A hardness, and elongation. The morphological behavior was studied by scanning electron microscopy. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 1029–1034, 2004     

Sound absorption properties of polyurethane/nano‐silica nanocomposite foams

In this study, polyurethane (PU)/nano‐silica nancomposite foams were prepared. The effects of isocyanate index, cell size, density, and molecular weight of polyols on the sound absorption ratio of PU/nano‐silica foams were investigated. With increasing nano‐silica content, the sound absorption ratio of PU/nano‐silica foams increases over the entire frequency range investigated in this study. Decrease of isocyanate index, cell size, and increase of density leads to the increase of sound absorption ratio of PU/nano‐silica foams. PU/nano‐silica foams have a broad T_g centered around room temperature by decreasing molecular weight of polyol resulting in good sound absorbing ability. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Flexible polyurethane foams modified with biobased polyols: Synthesis and physical‐chemical characterization

A series of flexible polyurethane foams with different polyol compositions were synthesized through the replacement of a portion of the petroleum‐based polyether polyol with biobased polyols, namely, glycerol (GLY) and hydroxylated methyl esters (HMETO). HMETO was synthesized by the alkaline transesterification of tung oil (TO; obtaining GLY as a byproduct) and the subsequent hydroxylation of the obtained methyl esters with performic acid generated in situ. FTIR spectroscopy, ¹H‐NMR, and different analytical procedures indicated that the hydroxyl content increased significantly and the molecular weight decreased with respect to those of the TO after the two reaction steps. The characterization of the obtained foams, achieved through the measurement of the characteristic reaction times, thermal and dynamic mechanical analysis, scanning electronic microscopy, and density measurements, is reported and discussed. The most important changes in the modified foams were found with the addition of GLY to the formulation; this led to an increased foam density and storage rubbery modulus, which were associated with a higher crosslinking density because of the decrease in the chain length between crosslinking points. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43831.     

Biodiesel from rapeseed oil,methanol and KOH. 3. Analysis of composition of actual reaction mixture

Detailed analysis is described of the samples taken after suitable reaction times from the actual reaction mixture during the production of biodiesel fuel using methanolysis of rapeseed oil catalyzed by KOH. Three methods for stoppage of reaction (neutralisation of catalyst, dilution by two suitable solvents) in the sample are used. The contents of mono‐, di‐ and triacylglycerols, methylesters of fatty acids (biodiesel) and potassium salts of fatty acids of rapeseed oil, glycerol (by HPLC method), basicity (by potentiometric titration) and water (by GC and Karl‐Fischer method) in the samples are determined. An example of these determinations is described.     

Preparation and Characterization of Sustainable Polyurethane Foams from Soybean Oils

Polyol derived from soybean oil was made from crude soybean oil by epoxidization and hydroxylation. Soy-based polyurethane (PU) foams were prepared by the in-situ reaction of methylene diphenyl diisocyanate (MDI) polyurea prepolymer and soy-based polyol. A free-rise method was developed to prepare the sustainable PU foams for use in automotive and bedding cushions. In this study, three petroleum-based PU foams were compared with two soy-based PU foams in terms of their foam characterizations and properties. Soy-based PU foams were made with soy-based polyols with different hydroxyl values. Soy-based PU foams had higher T _g (glass transition temperature) and worse cryogenic properties than petroleum-based PU foams. Bio-foams had lower thermal degradation temperatures in the urethane degradation due to natural molecular chains with lower thermal stability than petroleum skeletons. However, these foams had good thermal degradation at a high temperature stage because of MDI polyurea prepolymer, which had superior thermal stability than toluene diisocyanate adducts in petroleum-based PU foams. In addition, soy-based polyol, with high hydroxyl value, contributed PU foam with superior tensile and higher elongation, but lower compressive strength and modulus. Nonetheless, bio-foam made with high hydroxyl valued soy-based polyol had smaller and better distributed cell size than that using low hydroxyl soy-based polyol. Soy-based polyol with high hydroxyl value also contributed the bio-foam with thinner cell walls compared to that with low hydroxyl value, whereas, petroleum-based PU foams had no variations in cell thickness and cell distributions.     

Eco-friendly foams of castor oil based-polyurethane with Artemisia residue fillers for discarded vegetable oil sorption

In this article, a new approach is applied to reuse Artemisia residue (AR) as filler in polyurethane (PU) foam for vegetable oil sorption for discarded cooking oil applications. The pristine PU and PU/X%AR foams (X stands for AR content of 5–20%wt/wt) were characterized by SEM, density, contact angle (CA), thermogravimetric analysis, and Fourier transform infrared spectroscopy. The influence of two experimental factors, such as contact time (30–180 s) and initial vegetable oil concentration (20–200 g/L), was investigated in vegetable oil and vegetable oil/mineral water systems. The AR loading of the foams increased the foams' density and influenced the morphological, physical, thermal, and sorption properties. The PU/20%AR sample presented the highest CA (122.5°) and the best sorption capacity and efficiency in both systems due to the small pores size and higher frequency of pores. Langmuir and Freundlich isotherm models well defined the sorption mechanisms. The Langmuir model represented the best fit of experimental data for PU/20%AR with a maximum adsorption capacity of 16.86 g/g. The PU/20%AR presented reusability of 7 cycles, conserving their hydrophobicity after the process. Therefore, AR is an innovative route as fillers in PU foams for discarded vegetable oil sorption, and the circular economy can benefit from the reuse of discarded vegetable cooking oil.     

Preparation of polyurethane foams using fractionated products in liquefied wood

Liquefaction of sawdust was studied using glycerol and methanol as mix solvents. A new bio‐polyol product consisting of high purity multi‐hydroxy compounds was obtained by precipitation of the hydrophobic organics from the liquefied product in an aqueous solution. As identified by GC‐MS, the dominate components in bio‐polyol were glycerol, glycerol derivatives, and multiple types of sugar derivatives. By using the mass ratio of m (sawdust) : m (glycerol) = 1 : 1, the total content of multi‐hydroxy compounds reached 90.84%. The hydroxyl number of the bio‐polyol was 1287 mgKOH/g with a rotational viscosity of 1270 cP. Preparation of polyurethane foams using bio‐polyol and isocyanate was also studied. Water was used as an environmental friendly blowing agent. The factors that influence the cell structure of foams (i.e., catalyst, dosage of blowing agent, and mass ratio of bio‐polyol to PEG‐400 were studied. The compressive strength of the synthesized foam was 150 Kpa, which met the requirement of Chinese specification for rigid foams. The synthesized foams were characterized by FTIR, SEM, and TG. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40096.     

Preparation of semirigid polyurethane foam with liquefied bamboo residues

Bamboo residues were liquefied by using a solvent mixture consisting of polyethylene glycol 400 and crude glycerol (4/1, w/w) with 98% sulfuric acid as catalyst at 160°C for 120 min. The liquefied bamboo had hydroxyl values from 178 to 200 mg KOH/g and viscosities from 507 to 2201 mPa S. The obtained bamboo‐based polyols were reacted with various amounts of polyaryl polymethylene isocyanate (PAPI), using distilled water as blowing agent, silicone as surfactant, and triethylenediamine and dibutyltine dilaurate as cocatalyst to produce semirigid polyurethane (PU) foams. The [NCO]/[OH] ratio was found to be an important factor to control the mechanical properties of PU foams. At a fixed [NCO]/[OH] ratio, both density and compressive strength of PU foams decreased with the increase of bamboo content. The microstructure of PU foams indicates that [NCO]/[OH] ratios are important for cell formation and chemical reactions. The uniformity and cell structure of the foams are comparable to their corresponding compressive strengths. Moreover, the thermogravimetry analysis showed that all the semirigid PU foams had approximately the same degradation temperature of about 250 to 440°C. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Polyurethane foams based on crude glycerol-derived biopolyols: One-pot preparation of biopolyols with branched fatty acid ester chains and its effects on foam formation and properties

Environmentally friendly biopolyols have been produced with crude glycerol as the sole feedstock using a one-pot thermochemical conversion process without the addition of extra catalysts and reagents. Structural features of these biopolyols were characterized by rheology analysis. Rigid polyurethane (PU) foams were obtained from these crude glycerol-based biopolyols and the foaming mechanism was explored. Investigations revealed that partial carbonyl groups hydrogen-bonded with N–H were replaced by aromatic rings after the introduction of branched fatty acid ester chains in the “urea rich” phase, and that distinct microphases had formed in the foams. Studies showed that branched fatty acid ester chains in the biopolyols played an important role in reducing the degree of microphase separation and stabilizing bubbles during foaming processes. PU foams with thermal conductivity comparable to commercial products made from petroleum-based polyols were obtained. These studies show the potential for development of PU foams based on crude glycerol, a renewable resource.     

Open‐cell polypropylene/polyolefin elastomer blend foams fabricated for reusable oil‐sorption materials

The fabrication of high‐performance oil sorbents is of great significance for oil spill cleanup. The main objective of this study was to prepare open‐cell polypropylene/polyolefin elastomer (PP/POE) blend foams for fabrication of reusable sorbents for oil sorption. Open‐cell PP/POE blend foams were prepared via continuous‐extrusion foaming using supercritical carbon dioxide as the blowing agent. The interconnected open‐cell structure was characterized by scanning electron microscopy. The hydrophobicity and lipophilicity of PP/POE open‐cell foams were revealed by tests of contact‐angle measurement, water and cyclohexane sorption on the foam surface, CCl₄ and cyclohexane sorption in water, and oil/water separation. Further, the sorption tests indicated that PP/POE blend foams showed larger oil‐uptake capacities than pure PP foams. In addition, cyclic compression tests showed that PP/POE open‐cell foams had excellent ductility and significantly improved recoverability compared to pure PP foams. In cyclic sorption–desorption tests, the sorption kinetics was studied in terms of capacity and saturation time, showing that PP/POE foams kept larger sorption capacities for 10 cycles, with larger sorption rates and good reusability. Based on the high open‐cell content, the good hydrophobic and oleophilic properties, the high oil‐sorption capacity, the improved recoverability, the large sorption rate, and the good reusability in cyclic oil‐sorption performance, the PP/POE open‐cell foams have shown promise as potential oil sorbents in applications for oil spill cleanup. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43812.     

Physical properties of new polyurethanes foams from benzene polyols synthesized from erucic acid

High density triol‐based polyurethane (PU) foams were developed from aromatic triol isomers prepared from erucic acid. The triol monomers were crosslinked with 4,4′‐diphenylmethane diisocyanate (MDI) into PU foams. The foam's properties were studied by Fourier transform infrared (FTIR) spectroscopy, X‐ray diffraction (XRD), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), scanning electron microscopy (SEM), and thermogravimetric analysis (TGA). The foams were analyzed for closed cell content and compression strength. The effect of the benzene ring in the polyol structure on the physical properties of these new PU foams was compared with high density foams made from aliphatic polyols originating from canola oil. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Effect of different concentration of rapeseed‐oil‐based polyol and water on structure and mechanical properties of flexible polyurethane foams

Flexible polyurethane foams (FPURFs) with varied concentration of water from 3.2 to 4.2% and rapeseed oil based polyol (ROP) in the range of 13–22% in polyol premix were obtained. Effects of changes in polyurethane (PUR) formulation on the foaming process and mechanical properties of FPURFs were analyzed. It was found that the change of water content in PUR formulation influences its foaming process. Higher water content in the PUR formulation increases the growth velocity and the temperature of reaction mixture. In the case of foams modified with ROP, an opposite effect can be observed, where higher content of that component resulted in overall downturn of the foaming process and decreases of registered temperature inside the foams core. An addition of ROP beneficially influences on foams cellular structure favoring creation of finer cells. Such modification of PUR formulation with ROP increased apparent density, reduced hardness, and resilience of flexible foams. What is more the support factor of FPURFs with ROP was higher in comparison to the reference foam. Along with higher water content in the PUR formulation, apparent density and hardness has decreased and foams ability to absorb energy has been increased. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42372.     

Surface‐modifiers of clay on mechanical properties of rigid polyurethane foams/organoclay nanocomposites

Three different surface modifiers, octadecyl trimethyl ammonium (ODTMA), octadecyl primary ammonium (ODPA), and decanediamine (DDA) were used to modify Na⁺? montmorillonite (MMT), and the resultant organoclays were coded as ODTMA‐MMT, ODPA‐MMT, DDA‐MMT, respectively. Rigid PU foams/organoclay composites were prepared by directly using organoclay as the blowing agent without the addition of water. Investigation shows that the morphology of the nanocomposites is greatly dependent on the surface modifiers of clay used in the composites. In detail, DDA‐MMT is partially exfoliated in the PU matrix with the smallest cell size, while two others are intercalated in the PU matrices with smaller cell sizes. The sequence of their cell sizes is pristine PU foams > rigid PU foams/ODTMA‐MMT > rigid PU foams/ODPA‐MMT > rigid PU foams/DDA‐MMT, and the average cell size of rigid PU foams/DDA‐MMT composites decreases evidently from 0.30 to 0.07 mm. Moreover, all rigid PU foams/organoclay composites show remarkable enhanced compressive and tensile strengths as well as dynamic properties than those of PU foams, and the enhancement degree coincides well with the relative extent of internal hydrogen bonding of materials and gallery spacing of organoclay. For example, in the case of rigid PU foams/DDA‐MMT composite, 214% increase in compressive strength and 148% increase in tensile strength compared with those of pure PU foams were observed. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Forest‐based resources as fillers in biobased polyurethane foams

Six fillers from forestry wastes (wood, bark, cones and needles from young pine trees, kraft lignin, and recycled paper sludge from industry wastes) were incorporated into polyurethane (PU)‐based foams prepared via free‐rise pouring method. Variable filler contents (1, 5, and 10 wt %) and NCO/OH ratios (0.6, 0.9, and 1.2) were investigated. A simple mixture (1:3) of castor oil and crude glycerin (byproduct from biodiesel production) was used as biobased polyol. The foam composites were investigated through spectroscopy, morphological, mechanical, and hygroscopic analyses. The addition of fillers decreased water uptake and yielded rigid PU systems with more homogenous cell structure. The 1% and 5% reinforcement wood were the most effective among the studied compositions, with better mechanical and hygroscopic performance, probably due the higher compatibility of the wood with the PU system, which promote urethanic bonds between filler and isocyanate, as indicated by wet chemical results and micrographs. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45684.