Preparation Of Polyurethane Foams Research Articles

The role of catalysis in the synthesis of polyurethane foams based on renewable raw materials

In the last years growing attention is paid to environmental concerns with a special attention to bio- and renewable resources as feedstock for the chemical industry as well as to heterogeneous catalytic processes as tools for the elimination of wastes. This paper describes the results obtained in the application of vegetable oils stabilized through a selective hydrogenation process for the preparation of polyols and therefore in the synthesis of flexible polyurethane foams which are the most common and widely used among polyurethane materials. The influence of a different catalytic system on gelling and blowing reactions was studied and then properties of obtained foams were compared. It was found that the selection of catalytic system during preparation of polyurethane foams substantially influenced the properties of the final materials.

Preparation of polyurethane foams using fractionated products in liquefied wood

AbstractLiquefaction 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.

Tertiary recycling of poly(ethylene terephthalate) wastes for production of polyurethane–polyisocyanurate foams

The present work aims at tertiary recycling of poly(ethylene terephthalate) (PET) wastes to derive raw materials for production of polyurethane–polyisocyanurate foams. The first step involves glycolytic depolymerization of PET in the presence of diethylene glycol (DEG), under the influence of microwave irradiation with an aim to reduce the energy intensiveness of the process. Experimental conditions like PET:DEG ratio and reaction time were optimized to maximize the extent of PET conversion. Multiple extrusion of PET led to reduction in its molecular weight, which increased its reactivity towards glycolysis. The time required for glycolytic depolymerization of PET could be significantly reduced by employing microwave irradiation instead of conventional thermal process. The glycolysate was subsequently reacted with two different diacids: adipic acid (AA) and sebacic acid (SA) to obtain aromatic oligoesters. For the purpose of comparison, analogous aliphatic oligoesters were also prepared by reacting AA and SA with DEG under similar reaction conditions. The oligoesters were subsequently employed as a raw material for the preparation of polyurethane foams by reacting with diphenylmethane diisocyanate. The hydroxyl:isocyanate ratio in the formulation was decreased to introduce isocyanurate linkages, which resulted in the formation of polyisocyanurate foams with high compressive strength. Various characterization techniques were employed to determine the effect of the aromatic phenyl group and chain length of the diacid on the mechanical and structural properties of the resultant foams.

Polyurethane Foams from Cellulosic Waste and Natural Oil-based Polyols – a Modified Approach

A modified approach was used to prepare polyurethane (PU) foams employing natural oil-based polyols. Functionalized polyols with different hydroxyl values were synthesized from glycoside obtained from waste paper and reacted with natural oils viz. castor oil and soy oil. The obtained polyols were used to prepare the TDI-adduct based foams. Their physical and thermal properties were studied and compared using compression tests and thermogravimetric analysis; their cellular structures were also investigated using scanning electron microscopy. Processing parameters such as cream, rising and gel times were determined for the reactivity of the prepared polyols. Confirmation of PU linkage was performed by FTIR. The prepared PU foams demonstrated compressive properties ranging from 0.2 to 1.2 MPa and microscopic studies of the foam cell structure indicated its possible use for insulation purposes.

Fractionation of the Biopolyols from Lignocellulosic Biomass for the Production of Rigid Foams

The objective of this investigation was to find a simple method for the production of phenolic-rich products and sugar derivatives via separation of liquefied lignocellulosic materials. After liquefaction, the liquefied products were separated by addition of a sufficient amount of water. It was found that those hydrophobic phenolics could be largely separated from aqueous solutions. Preparation of polyurethane foams using biopolyol and isocyanate was studied. Water was used as an environmentally friendly blowing agent. The factors influencing the cell structure of foams such as catalyst, dosage of blowing agent, and mass ratio of biopolyol to PEG were studied. The microstructure of synthesized foams was characterized by SEM.

Microwave assisted glycolysis of poly(ethylene terepthalate) for preparation of polyester polyols

AbstractThe generic aim of the present work is to reduce the time required for glycolytic depolymerization of PET by employing microwave irradiation instead of the conventional heating process. Glycolysis of PET was performed in the presence of glycols of different molecular weight under microwave irradiation. Experimental conditions like PET : glycol ratio, reaction time and concentration of glycerol were optimized to maximize the product yield. In the presence of ethylene glycol, bis‐(hydroxyethyl) terephthalate (BHET) could be obtained in excellent yields in significantly lesser time (30 min) as compared to 8–9 h by conventional heating process. The BHET yield could further be increased by a second step glycolysis of the residual oligomers. This increased efficiency of the microwave assisted process has been attributed to the high microwave absorption capacity of glycols which results from their high loss factor. PET could also be glycolysed in the presence of higher glycols, however the reactivity of diols was found to decrease with increase in the molecular weight. The polyols obtained were reacted with aromatic diphenylmethane diisocyanate to prepare polyurethane foams, which were characterized by various techniques for determination of their physical, mechanical and structural properties. The compressive strength of the polyurethane foams was found to be inversely proportional to the molecular weight of the glycolysed polyol used for its preparation. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Oligoeterole i pianki poliuretanowe z pierscieniem 1,3,5-triazynowym i atomami boru

Oligoetherols containing 1,3,5-triazine ring and boron atoms were synthesized in the reactions of N,N,N',N',N”,N”-hexakis(2-hydroxyethyl)melamine with boric acid, followed by reaction with alkylene carbonates. The structure and physical properties of the obtained oligoetherols were investigated. The oligoetherols were used for the preparation of polyurethane foams with improved thermal stability and reduced flammability. The properties of obtained foams were compared with those synthesized directly from melamine and alkylene carbonates.

Preparation of polyester polyols from unsaturated fatty acid

AbstractOleic acid is a typical unsaturated fatty acid that is found widely in vegetable oils. The objective of this investigation was to produce a new type of oleic‐based polyol from oleic acid. Possible advantages of this approach include the production of high‐performance polyurethane materials from renewable resources and value‐added research for oleic acid. Oleic‐based polyols were synthesized by a three‐step process consisting of epoxidation and ring‐opening reaction, followed by esterification. The synthesized polyols appeared as a viscous liquid at room temperature with hydroxyl numbers from 307 to 425 mg KOH/g. Preparation of polyurethane foams using oleic‐based polyols and isocyanate was studied. An environmentally friendly blowing agent, HCFC‐141b, together with a small amount of water, was used. The synthesized foams were characterized by FTIR, SEM, and TG/DSC. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Preparation of Polyurethane Foams Based on Liquefied Corn Stalk Enzymatic Hydrolysis Lignin

Preparation of Polyurethane Foams Based on Liquefied Corn Stalk Enzymatic Hydrolysis Lignin

The preparation of polyurethane foam combined with pH-sensitive alginate/bentonite hydrogel for wound dressings

Polyurethane (PU) foam was combined with protein drug-loaded pH-sensitive alginate-bentonite hydrogel for wound dressings. Alginate is a linear copolymer composed of 1–4-linked β-D-mannuronic acid (M) and its c-5-epimer α-Lguluronic acid (G). The amount of (M) and (G) and their sequential distribution are varied depending on the alginate source. Soluble sodium alginate can become a hydrogel when cross-linked with divalent cations and has widespread applications in the food, drink, pharmaceutical and bioengineering industries. Recently, it has been also proposed as a biomaterial for drug delivery systems. Bentonites are the natural inorganic polymers consisting of a large proportion of expandable clay minerals with a three-layer structure such as montmorillonite, beidellite, nontronite, etc. They are important adjutants and supports for medical products, and they have many useful physicochemical, mechanical, and biological properties such as absence of toxicity, indifference to other raw materials, sorption, swelling, and complex formation properties. Alginate-bentonite hydrogels were prepared at concentration ratios of 10/0, 7/3, 5/5, 3/7. PU foams were prepared using hydrophilic polyols. We investigated the controlled release of a protein drug from PU foam combined with alginate-bentonite hydrogel at different pH values of 4.2, 5.2, 7.2, 8.2. The mechanical properties and cytotoxicity tests of this foam were also studied.

Thermal and Morphological Properties of Polyurethane Foams Prepared from Microwave-assisted Glycolyzed Products of PET Bottles Wastes

Abstract Polyethylene terephthalate (PET) waste from post-consumer soft drink bottles was depolymerized under microwave energy instead of conventional heating with diethylene glycol (DEG) at the molar ratio between PET and DEG of 1:4 in a modified domestic microwave oven at the irradiation power of 600 W. Zinc acetate, sodium carbonate and sodium bicarbonate were used as a catalyst at 0.5% by weight of PET. It was reported that replacement of conventional heating with microwave energy shortened the chemical reaction time significantly. Polyurethane foams were then successfully prepared from the glycolyzed products by reacting them with polymeric diphenylmethane diisocyanate and polyethylene glycol as a chain extender. Thermal and morphological properties of the prepared polyurethane foams were then studied. It was found that the thermal behavior of the prepared foams was similar while their morphology was affected by the catalyst used. The most uniform cell structure was observed when the glycolyzed product that used sodium bicarbonate as a catalyst was used to prepare polyurethane foam.

Halogen‐free flame‐retardant rigid polyurethane foams: Effect of alumina trihydrate and triphenylphosphate on the properties of polyurethane foams

AbstractRigid polyurethane foam (PUF) filled with mixture of alumina trihydrate (ATH) and triphenyl phosphate (TPP) as fire retardant additive was prepared with water as a blowing agent. In this study, the ATH content was varied from 10 to 100 parts per hundred polyol by weight (php), and TPP was used at a higher loading of ATH (75 and 100 php) in a ratio of 1 : 5 to enhance the processing during PUF preparation. The effects of ATH on properties such as density, compressive strength, morphological, thermal conductivity, thermal stability, flame‐retardant (FR) behavior, and smoke characteristics were studied. The density and compressive strength of the ATH‐filled PUF decreased initially and then increased with further increase in ATH content. There was no significant change in the thermal stability with increasing ATH loading. We determined the FR properties of these foam samples by measuring the limiting oxygen index (LOI), smoke density, rate of burning, and char yield. The addition of ATH with TPP to PUF significantly decreased the flame‐spread rate and increased LOI. The addition of TPP resulted in easy processing and also improved FR characteristics of the foam. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Halogen-free, low flammability polyurethanes derived from deoxybenzoin-based monomers

Two novel deoxybenzoin-containing monomers, a diisocyanate and a diol, were synthesized and used to prepare polyurethane materials and foams. 4,4′-Diaminodeoxybenzoin was prepared by Ullmann coupling of 4,4′-dibromobenzil with tert-butyl carbamate. Reduction of one of the carbonyl groups, and t-Boc deprotection, gave the aromatic diamine, which was converted to 4,4′-deoxybenzoin diisocyanate (DBDI) with triphosgene. DBDI was then used to prepare two different polyurethanes, one by reaction with 1,3-propanediol, and the other by reaction with deoxybenzoin diol. The polyurethanes obtained from these reactions displayed low heat release capacity (HRC) values relative to conventional polyurethanes prepared from 4,4′-methyldiphenyl diisocyanate (MDI) and 2,4-toluene diisocyanate (TDI). Polyurethanes prepared in this study displayed HRC values as low as ∼130 J g−1 K−1, and char yields as high as ∼40%. In addition, deoxybenzoin-based oligomers containing hydroxyl end groups were also synthesized and used to prepare polyurethane foams that displayed markedly lower HRC values, and higher char yields, than conventional polyurethane foams, which burn readily and drip. Taken together, the integration of deoxybenzoin moieties into the diisocyanate or polyol component of the polymer structure is found to lower heat release rates and reduce flammability in the absence of any added flame retardant, such as halogenated compounds that represent health and environmental hazards.

Performance characterization of rigid polyurethane foam with refined alkali lignin and modified alkali lignin

The two kinds of rigid polyurethane (PU) foams were prepared with respectively adding the refined alkali lignin and alkali lignin modified by 3-chloro-1,2-epoxypropane to be instead of 15% of the polyether glycol in weight. The indexes of mechanical performance, apparent density, thermal stability and aging resistance were separately tested for the prepared PU foams. The results show that the mechanical property, thermal insulation and thermal stability for PU foam with modified alkali lignin are excellent among two kinds of PU foams and control samples. The additions of the refined alkali lignin and modified alkali lignin to PU foam have little effect on the natural aging or heat aging resistance except for decreasing hot alkali resistance apparently. Additionally, the thermal conductivity of modified alkali lignin PU foam is lowest among two kinds of PU foams and control samples. The alkali lignin PU foam modified by 3-chloro-1,2-epoxypropane could be applied in the heat preservation field.

Comparison of Environmentally Friendly, Selective Polyurethane Catalysts

Selected commercially available amines, including N-substituted morpholines, were evaluated as single catalysts and as catalyst mixtures for polyurethane foam preparation. The motivation was the search for economically and environmentally attractive replacements of “classical” catalysts, like diazabicyclooctane, dibutyltindilaurate, and N,N-bis(2-dimethylaminoethyl)methylamine. Especially interesting was replacing dibutyltindilaurate, and also the possibility of using reactive catalyst derivatives that would be incorporated into polyurethanes, thus reducing the content of volatile organic compounds in the polymer. The catalysts were tested on a α,ω-polybutadienediol + toluenediisocyanate-based system. In some experiments, toluenediisocyanate was replaced by the more reactive and environmentally friendly 4,4′-Methylenebis(phenylisocyanate) and polybutadienediol by polypropyleneglycol.

Atmospheric Pressure Liquefaction of Dried Distillers Grains (DDG) and Making Polyurethane Foams from Liquefied DDG

In this study, dried distillers grains (DDG) was liquefied in acidic conditions at atmospheric pressure, and polyurethane foams were subsequently prepared from the liquefied DDG. Liquefaction was examined over a range of conditions including liquefaction time of 1-3 h, temperature of 150-170 degrees C, sulfuric acid (as catalyst) concentration of 1.0-3.0 wt%, and liquefaction solvent (ethylene carbonate) to DDG ratio of 3:1-5:1. The bio-polyols in the liquefied DDG were rich in hydroxyl groups, which can react with methylene diphenyl diisocyanate (MDI) to form cross-linked polyurethane networks. The biodegradability of the prepared polyurethane foams was also evaluated. This study strives to broaden the application of DDG as a feedstock for bio-polyurethane preparation.

Structural, thermal, and mechanical properties of polyurethane foams prepared with starch as the main component of polyols

In this study, rigid polyurethane foams were prepared using starch as the main component of polyols and their structural, thermal, and mechanical properties were investigated. The starch content in polyols was 30∼50 wt.%. The prepared polyurethane foams had a cell structure. When the starch content and -NCO/-OH molar ratio (TS4-05, TS3-07, and TS3-05) was low, polyurethane foams were not formed. To confirm the formation of a urethane linkage between -OH of the starch and -NCO of the 2,4-TDI, FT-IR spectroscopic analysis was performed. The thermal properties of polyurethane foams were analyzed by DSC and TGA. DSC thermograms showed two endothermic peaks: a sharp peak at a lower temperature and a broad peak at a higher temperature. Both peaks were shifted to higher temperature with starch content in polyols and -NCO/-OH molar ratio. Thermal degradation of polyurethane foams began at a lower temperature and ended at a higher temperature than that of starch. The impact resistance, compressive stress and modulus of polyurethane foams increased with -NCO/-OH molar ratio and starch content.

Synthesis of polyetherols from melamine and propylene carbonate. II

AbstractResults of the reaction of melamine with propylene carbonate in the synthesis of polyetherols with 1,3,5‐triazine rings are presented. Optimal conditions of synthesis of the polyetherols are presented and the products characterized by determining selected physical properties and by using spectral methods [1H‐NMR, IR, mass spectroscopy (MS) electrospray ionization (ESI)]. The content of side products was established by GLC. The resulting polyetherols have been found suitable for preparation of polyurethane foams of improved thermal stability. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 104–115, 2003

Liquefaction of corn bran (CB) in the presence of alcohols and preparation of polyurethane foam from its liquefied polyol

Liquefaction of corn bran (CB) in the presence of alcohols and preparation of polyurethane foam from its liquefied polyol

Use of microorganism-immobilized polyurethane foams to absorb and degrade oil on water surface.

Highly oil-absorbent polyurethane foam (PUF) materials were obtained by polymerizing polyether polyol mixture and carbodiimide-modified D-methyl diisocyanate in a weight ratio of 10:2. The foam materials were prepared to contain inorganic nutrients (slow-release fertilizer; SRF) and oil-degrading yeast cells, Yarrowia lipolytica 180, to be applied for removal of oil films on surface waters through absorption and biodegradation after oil spills. PUFs absorbed 7-9 times their own weight of Arabian light crude oil and the oil absorbency appeared to improve as the ratio of surface area to foam weight increased. PUFs showed excellent floatability which was maintained for more than 6 months in sea water, and less than 5% of the absorbed oil was released when the foams were left on water for more than 10 days. For immobilization of yeast cells into PUFs, various immobilization techniques were tested to compare their oil degrading ability and the maintenance thereof. All immobilized cells showed oil degrading abilities as good as those of free cells immediately after the preparation of PUFs, however, the activity of chitin-immobilized cells remained at a high level for the longest period of preservation. The high efficiency of oil absorption and oil degradation by PUF-immobilized yeast cells suggested that PUF-immobilized cells have a high potential as a bioremediation technique for the treatment of oil films on surface waters.