Polyurethanes from vegetable oils and applications: a review

Among the various polymers, polyurethanes are likely the most versatile specialty polymers. These polymers are widely used in many applications such as foams, coatings, insulations, adhesives, paints and upholstery. Similar to many polymers, polyurethanes relies on petrochemicals as raw materials for its major components. Indeed, nowadays many researches have focused to replace petroleum-based resources with renewable ones to improve polyurethanes sustainability. Polyurethanes are synthesized by polymerization reactions between isocyanates and polyols. Only a few isocyanates are commonly used in polyurethane industries, while a variety of polyols are available. Renewable materials such as vegetable oils are promising raw materials for the manufacture of polyurethane components such as polyols. Vegetable oils are triglycerides which are the esterification product of glycerol with three fatty acids. Several highly reactive sites including carbon-carbon double bond, allylic position and ester group in triglycerides and fatty acids open the opportunities for various chemical modifications for new polyol with different structures and functionalities. Different methods such as are epoxidation, ozonolysis, hydroformylation and metathesis have been widely studied to synthesise bio-polyol from vegetable oil for new polyurethanes, which depend on triglyceride and isocyanate reagents used. The incorporation of a vegetable oil moiety can enhance thermal stability and mechanical strength of polyurethanes. Similar to bio-polyol, the development of renewable resource based bio-isocyanates is also gained attention to produce entirely bio-polyurethanes. This article comprehensively reviews recent developments in the preparation of renewable resource based polyols and isocyanates for producing polyurethanes and applications.     

Flame-retarding materials. II. Synthesis and flame-retarding properties of phosphorus-on-pendent and phosphorus-on-skeleton polyols and the corresponding polyurethanes

A phosphorus-on-skeleton compound was synthesized by reacting phenyl dichlorophosphate (PDCP) with 2-hydroxyethyl methacrylate (HEMA). This monomer was then copolymerized with other acrylic monomers to form a hydroxy-containing copolymer, which was then used as the polyol in the synthesis of a polyurethane. Phosphorus-on-pendent copolymers and phosphorus-free copolymers and their corresponding polyurethanes were also prepared for comparison with the phosphorus-on-skeleton material in terms of their flame-retardant properties. The flame retardancy and degradation mechanism of these copolymers and polyurethanes were analyzed with thermogravimetric analysis (TGA) and infrared spectroscopy. Although those phosphorus-on-skeleton copolymer polyols have less flame-retarding ability than that of the phosphorus-on-pendent copolymer polyol because of less phosphorus content, it was evident that the phosphorus-on-skeleton polyurethanes were more effective flame retardants than the phosphorus-on-pendent polyurethanes. This was attributed to the fact that the crosslinking arising from the phosphorus-on-skeleton copolymer polyols has a tremendous effect on the flame-retarding ability of the corresponding polyurethanes. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 343–357, 2001     

Synthesis of trimethylolpropane esters of tall oil fatty acids and properties of polyurethane coatings on their basis

Tall oil fatty acids (TOFA) were esterified with trimethylolpropane (TMP) without a catalyst at different molar ratios of TMP to TOFA. A molar ratio was defined, at which a polyol stable in long-term storage, with the maximum content of TMP monoesters, was synthesized. Fourier transform infrared spectroscopy and gas chromatography were used for the identification of the polyols’ chemical structure and composition. Based on the synthesized polyols, polyurethane coatings were prepared. The effect of the isocyanate index and concentration of traditional Sn-based and less toxic Bi-based catalysts on the gel time of the polyurethane composition, and the mechanical and thermal properties of the coatings was studied. It was found that the new coatings had high tensile strength and modulus of elasticity, comparable with the strength and modulus of the polyurethane based on diethanolamides of TOFA. The initial temperature of decomposition of these coatings was higher than that of the polyurethanes based on esters of TOFA and a number of uralkyds. The coatings based on TMP esters of TOFA were obtained without the use of solvents, and potentially, these esters can be used in spray-applied VOC-free polyurethane coatings’ formulation.     

Synthesis of new polyester polyols from epoxidized vegetable oils and biobased acids

Biobased polyols were synthesized from reaction between epoxidized soybean oil and lactic, glycolic, or acetic acids. Polyols were characterized by NMR, alcohol and acid titration, and SEC. These analyses allowed to determine an average hydroxyl functionality between 4 and 5, with an oligomer content close to 50 wt%. Synthesized polyols were formulated with isocyanate to yield polyurethanes (PUs). Thermal and mechanical properties of obtained materials showed that synthesized polyols lead to rigid and brittle material with Young moduli higher than 900 N/mm² at RT and with T_g values around 50°C. Practical application: The products of the chemistry described in this contribution, i.e.: polyol from vegetable oils and lactic, glycolic, or acetic acids, provide biobased building blocks for further PUs syntheses by reaction with diisocyanates. The obtained PUs are partially biobased and may be applied as binders and coatings.     

Biobased flexible polyurethane foams manufactured from lactide-based polyester-ether polyols for automotive applications

In this study, biobased polyester-ether polyols derived from meso-lactide and dimer acids were evaluated for flexible polyurethane foams (PUF) applications. Initially, the catalyst concentration was optimized for the biobased PUF containing 30% of biobased polyol (70% petroleum-based polyol). Then, the same formulation was used for biobased PUF synthesis containing 10%–40% of biobased polyols. The performance of biobased PUF was compared with the performance of the control foam made with 100% petroleum-based polyol. The characteristic times (cream, top of the cup, string gel, rise, tack-free) of biobased PUF were determined. The biobased PUF were evaluated for the mechanical (tensile and compressive) and morphological properties. As the wet compression set is important for automotive applications, it was measured for all biobased PUF. The thermal degradation behavior of biobased PUF was also evaluated and compared with the control foam. The effect of different hydroxyl and acid values of polyols on the mechanical properties of biobased PUF is also discussed. The miscibility of all components of PUF formulations is crucial in order to produce a foam with uniform properties. Thus, the miscibility of biobased polyols with commercial petroleum-based polyol was studied.     

A Review on Waterborne Thermosetting Polyurethane Coatings Based on Castor Oil: Synthesis,Characterization, and Application

Waterborne polyurethane coatings made from castor oil as polyol resource, replacing oil from fossil fuels are attracting lot of recognition during recent decades. In this review, castor oil and its modifications to synthesize various biobased waterborne polyurethane and their nanocomposite systems have been addressed. Various synthesis procedures for waterborne polyurethane dispersions and their applications as a coating material have been described. This review will be helpful to the green research community for selection of monomer and further development of biobased waterborne polyurethane utilizing advanced technology.     

Synthesis and Characterization of the Different Soy-Based Polyols by Ring Opening of Epoxidized Soybean Oil with Methanol, 1,2-Ethanediol and 1,2-Propanediol

Three soy-based polyols intended for application in polyurethanes were prepared by ring opening the epoxy groups in epoxidized soybean oil (ESO, 0.385 mol/100 g epoxy rings) with methanol, 1,2-ethanediol and 1,2-propanediol in the presence of tetrafluoroboric acid catalyst. The effect of the different opening reaction reagents, different low molecular weight alcohols, on the polyols was investigated by spectroscopic, chemical and physical methods. The viscosities, viscous-flow activation energies, molecular weight and melting point of the samples increased in the following order: polyol (3) > polyol (2) > polyol (1) > ESO [polyol (1); polyol (2) and polyol (3) represented the samples synthesized from the same epoxidized soybean oil generated by opening reactions with methanol, 1,2-ethanediol and 1,2-propanediol, respectively]. All the samples were crystalline solids below their melting temperature, displaying multiple melting point peaks. Compared with polyol (1), polyol (2) had a primary hydroxyl group, promoting the reactive activity of the polyol with isocyanates; polyol (3) contained large numbers of hydroxy groups, improving the properties of polyurethanes.     

Highly functional biobased polyols and their use in melamine–formaldehyde coatings

Highly functional sucrose soyate polyol (SSP) resins were synthesized by ring-opening epoxidized sucrose soyate with methanol or ethanol and were subsequently crosslinked with a melamine–formaldehyde (MF) resin in the presence of an acid catalyst or blocked acid catalyst. The biobased polyols were characterized by Fourier transform infrared spectroscopy, gel permeation chromatography, proton nuclear magnetic resonance spectroscopy, Brookfield viscosity, and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. The thermal properties of the biobased MF coatings were studied using differential scanning calorimetry and dynamic mechanical analysis. As controls, a soybean oil polyol (SBOP) with lower functionality and a commercial polyester polyol were studied for comparison. Overall, MF coatings formulated with SSPs showed superior properties to coatings formulated with SBOP and comparable properties to the commercial polyester which was attributed to the high hydroxyl functionality.     

Preparation and properties of eco-friendly two pack PU coatings based on renewable source (sorbitol) and its property improvement by nano ZnO

Today most of the coating formulations are based on petroleum sources, which are limited. Therefore, it is necessary to use any eco-friendly renewable source for making polymers, as they are renewable and may be non-hazardous, easily available and cheaper. In the present work we selected sorbitol as a renewable source, which is derived from naturally occurring polymer, i.e., cellulose. The technology of converting cellulose to sorbitol is well established. Hence we directly utilized sorbitol in the preparation of polyester polyols. These polyols were synthesized with the help of sorbitol, 1,2,3,6-tetrahydro phthalic anhydride, adipic acid, diethylene glycol and zinc acetate (catalyst). The synthesized polyols were characterized for their acid value, hydroxyl value, molecular weight, IR spectroscopy, etc. The polyol is further used in polyurethane coatings after reacting with polyisocyanates. For further improvement in properties, these coatings were prepared by adding nano sized ZnO. This ZnO was prepared in the laboratory and characterized for its size by SEM. The prepared PU coatings were analyzed for their coating properties such as gloss, scratch resistance, flexibility, impact test, chemical properties and anticorrosive properties.     

Synthesis and characterization of polyurethane coatings derived from polyols synthesized with glycerol, phthalic anhydride and oleic acid

Polyester polyols, with various oleic acid contents were used in the preparation of polyurethane (PUR) coatings. The polyols were designated as Alk28, Alk40 and Alk65, in which 28, 40 and 65 represents the percentages of oleic acid in the respective formulations. The physical properties of the polyols such as acid value and hydroxyl value have been determined and the infrared (IR) spectroscopic analysis of the polyols is reported. The polyols were reacted with aromatic isocyanate (toluene 2,4-diisocyanate, TDI) to form PUR coatings. The effects of varied NCO/OH ratio and oleic acid content of polyols on physical properties of PUR coatings on mild steel panel were determined. The characterization of PUR coatings carried out by IR spectroscopic analysis and physico-chemical properties such as drying time, pencil hardness, adhesion properties, solvent resistance and corrosion/chemical resistant determination were reported. The coatings obtained from polyol Alk28, exhibits the best overall properties followed by Alk40. PUR coatings from Alk65 were softer. As the NCO/OH ratio of the coatings increased, there were progressive increases in mechanical and anticorrosive properties for all the coatings. Overall, these studies showed that the material holds promise for use as effective surface coating compound by designing the formulation of the desired performance.     

Energetic polyurethanes from branched glycidyl azide polymer and copolymer

Branched glycidyl azide polymer (GAP) and glycidyl azide–ethylene oxide copolymer (GEC) have been prepared by a degradation process using different polyols in the synthesis reaction. The azido homopolymers and copolymers were characterized by gel permeation chromatography and viscometry techniques. Energetic polyurethanes were then obtained from the curing of branched glycidyl azide polymers and copolymers using isophorone diisocyanate as a curing agent. The polyurethanes were characterized using thermomechanical analysis and tensile testing. The polyurethane copolymers have generally a higher elongation at break and a lower glass transition temperature than their GAP homopolymer counterparts. The polyol reactant used in the synthesis of GAP and GEC had an effect on the mechanical properties of the polyurethanes obtained from these polymers. © 1996 John Wiley & Sons, Inc.     

Synthesis and characterization of polyurethane coatings derived from polyols synthesized with glycerol,phthalic anhydride and oleic acid

Polyester polyols, with various oleic acid contents were used in the preparation of polyurethane (PUR) coatings. The polyols were designated as Alk28, Alk40 and Alk65, in which 28, 40 and 65 represents the percentages of oleic acid in the respective formulations. The physical properties of the polyols such as acid value and hydroxyl value have been determined and the infrared (IR) spectroscopic analysis of the polyols is reported. The polyols were reacted with aromatic isocyanate (toluene 2,4-diisocyanate, TDI) to form PUR coatings. The effects of varied NCO/OH ratio and oleic acid content of polyols on physical properties of PUR coatings on mild steel panel were determined. The characterization of PUR coatings carried out by IR spectroscopic analysis and physico-chemical properties such as drying time, pencil hardness, adhesion properties, solvent resistance and corrosion/chemical resistant determination were reported. The coatings obtained from polyol Alk28, exhibits the best overall properties followed by Alk40. PUR coatings from Alk65 were softer. As the NCO/OH ratio of the coatings increased, there were progressive increases in mechanical and anticorrosive properties for all the coatings. Overall, these studies showed that the material holds promise for use as effective surface coating compound by designing the formulation of the desired performance.     

不同合成工艺的聚醚多元醇对聚氨酯弹性体性能的影响

分别采用低不饱和度聚醚多元醇DL-1000D和氧氧化钾体系聚醚多元醇DL-1000与TDI-80反应合成出聚氨酯预聚体,比较了2种不同聚醚多元醇合成预聚体的工艺性能、预聚体的稳定性和由它们合成聚氨酯弹性体制品的力学性能和耐磨性能。结果表明,二者的丁艺性能和稳定性相当,采用前者合成的聚氨酯弹性体的力学性能比后者高10％左右,耐磨性能按阿克隆磨耗测试提高17．6％。     

Effect of dicarboxylic acids on the performance properties of polyurethane dispersions

A series of low molecular weight linear polyester polyols were synthesized by using various diacids, neopentyl glycol, as a diol, and a trimethylol propane, as a branching monomer. Polyurethane dispersions were prepared primarily from isophorone diisocyanate, polyester polyol, and dimethylol propionic acid, as potential ionic center for water dispersibility, and were subsequently chain extended with ethylene diamine. The effect of polyester polyols based on variable diacids, on the physico‐chemical and thermal properties of polyurethane dispersions were evaluated by hardness, flexibility, impact resistance, solvent resistance, thermogravimetric analysis, and differential scanning calorimetry. Particle size was evaluated by particle size analyzer. It was observed that the number of alkylene groups present in the polyester polyol soft segment in addition to its molecular weight had a pronounced effect on the particle size, physico‐chemical, and thermal properties. With a proper selection of the soft segment, it is possible to fine‐tune properties of aqueous polyurethane dispersion coatings with respect to the final application. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Moisture-cured polyurethane based on polyester and polycarbonate polyols

Moisture-cured polyurethanes were prepared by reacting toluene diisocyanate and sebacic acid-based hydroxy esters such as ethylene glycol sebacate, propylene glycol sebacate, diethylene glycol sebacate, and polyester polyols such as poly(ethylene glycol sebacate), poly(propylene glycol sebacate), poly(diethylene glycol sebacate), and poly(butane diol sebacate). The effect of molecular weight of the esters on film properties and the catalytic effect of 3–5% triethylamine, triethanolamine, and 2-diethylaminoethanol on curing of such films were investigated. Polyurethanes were also prepared using a blend of poly(butane diol carbonate) polyol with polyester polyols. Best polyurethane compositions were obtained when sebacic acid-based polyester polyols were blended with poly(butane diol carbonate) polyol in the ratio of 3:2. These polyurethanes show good tensile strength (120–215 kg/cm²) and elongation (340–460%) properties, having high melting points (247–268°C) and good resistance to solvents and chemicals. Moreover, they are colorless and transparent.     

Synthesis and properties of polyurethane networks derived from new soybean oil‐based polyol and a bulky blocked polyisocyanate

BACKGROUND: Developing vegetable oil‐based polyols for polyurethane manufacturing is becoming highly desirable for both economic and environmental reasons. Most vegetable oils do not bear hydroxyls naturally. The objective of this work was to prepare a new soybean oil‐based polyol with high functionality of hydroxyl groups and built‐in (preformed) urethane bonds. RESULTS: A facile and improved method was developed for the transformation of epoxidized soybean oil into carbonated soybean oil under ambient pressure of CO₂ gas, with tetrabutylammonium bromide/calcium chloride as catalyst/co‐catalyst couple. Ring‐opening reaction of the carbonated oil with ethanolamine led to the desired polyol. A one‐pack polyurethane system was prepared via combination of the polyol and a blocked polyisocyanate. The polyol and final polyurethanes were fully characterized, and their physical, mechanical, viscoelastic and electrical insulating properties were studied. CONCLUSION: The application of this newly developed soybean oil‐based polyol for preparation of electroinsulating casting polyurethanes was examined. The prepared soy‐based polyurethanes offered excellent thermal and electrical insulating properties. Also, tunable physical and chemical properties for the final polyurethanes were achieved by replacing part of the soybean oil‐based polyol with poly(propylene glycol) (M_n = 1000 g mol^?1). Copyright © 2008 Society of Chemical Industry     

Fully biobased polyester polyols derived from renewable resources toward preparation of polyurethane and their application for coatings

Renewable resources such as isosorbide and dimer acid were used to prepare fully biobased polyester polyols and polyurethane (PU) coatings. The structural features of polyester polyols were studied by end-group analysis and spectroscopic methods. Then polyols were utilized in the preparation of PU coatings by reacting with diisocyanate. The prepared PU coatings were tested for both mechanical and chemical testings, which involved gloss, cross-cut adhesion, pencil hardness, anticorrosion performance by immersion and Tafel plot methods, and chemical resistance against water, solvent, and acid media. The prepared PUs were also tested for their thermal stability using a thermogravimetric analyzer and surface morphology by a scanning electron microscopy. Tested mechanical properties, chemical resistance, and thermal stability results demonstrated that the renewable sources used in the preparation of PU coatings can be good substitutes over petroleum resources. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47558.     

The relative physical and thermal properties of polyurethane elastomers: Effect of chain extenders of bisphenols,diisocyanate, and polyol structures

Polyurethane elastomers based on polyols such as polycaprolactone diol of molar mass 2000 and polytetramethylene glycol of molar mass 2000; diisocyanantes such as diphenyl methane 4,4′ diisocyanate and dicyclohexyl methane 4,4′ diisocyanate; and chain extenders such as bisphenol-A, bisphenol-S,bisphenol-AF, and their brominated derivatives were synthesized. The effects of polyol, diisocyanate, and chain extender on the physical and thermal properties were also studied. The polyurethane elastomers were investigated by X-ray diffraction (XRD), differential scanning calorimetry, thermogravimetric analysis, and dynamic mechanical analysis. Their limiting oxygen indexes (LOIs), solubilities, tensile strengths, hardnesses, and elongations were also determined. XRD analyses revealed that all of the polyurethanes were semicrystalline. However, the addition of bromine atoms in the polyurethanes markedly decreased their degrees of crystallinity. The brominated polyurethane elastomers have good flame retardancy, as indicated by large LOIs. All of the unbrominated polyurethanes showed good mechanical properties and high thermal stabilities. Polyurethanes based on bisphenol-S had lower solvent resistance caused by the dipolar nature of sulfonyl groups in the polymer chains. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 1251–1265, 1997     

Synthesis,characterization, and properties of novel polyetherester polyols and developed polyurethanes

Three kinds of cyclic anhydrides, which stand for aliphatic anhydride, aromatic anhydride, and anhydride containing double bond: succinic anhydride, phthalic anhydride, and maleic anhydride have been copolymerized with propylene oxide and low molecular weight polyoxypropylenediol via ring‐opening copolymerization initiator by double metal cyanide complex catalyst to synthesis a series of polyetherester (PEE) polyols. The structure of the obtained copolymers was confirmed by several analysis methods. Three kinds of polyetherester polyurethane (PEEPU) were thus synthesized by polymerization of as‐synthesized PEE polyol with 4,4′‐diphenylmethane diisocyanate. The mechanical properties of the obtained PEEPU were tested. The results showed that the mechanical properties of three polyurethanes are different based on their structure and composition. The inducing of the rigid phenyl group in the soft segment can improve the mechanical strength remarkably. The influences of ester content in soft segment and the hard segment content on the mechanical properties of PEEPU were studied. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 417–424, 2007     

Grafting of polyesters onto carbon whisker surface

Summary Polymerization of N-(p-aminobenzoyl)-caprolactam (PAC) in melts of polyols such as dihydroxy-terminated oligo(oxytetramethylene) with M_n=2000 g/mol at 200°C afforded stable dispersions of poly(p-phenylenebenzamide) whiskers in polyol. In spite of the low molecular weight of the polyaramide, which was isolated by solvent extraction, the microparticles are efficient reinforcing agents of polyurethanes because of the excellent interfacial adhesion resulting from covalent attachment of the polyols onto the microparticle surfaces. The role of the competing formation of p-aminobenzoate-terminated polyols via esterification of PAC was investigated. Morphological and mechanical properties of polyurethane microcomposites, prepared from poly(p-phenylenebenzamide)/poly(oxytetramethylene)diol dispersions and 4,4-diisocyanatodiphenylmethane, were determined as a function of the microparticle content. When compared to conventional polyurethanes, containing equivalent amounts of spherical organic and inorganic fillers, the microcomposites give higher Young's modulus, tensile strength without sacrificing high elongation at break.