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.     

Elaboration and Characterization of Advanced Biobased Polyurethane Foams Presenting Anisotropic Behavior

Biobased and open cell polyurethane (PU) foams are produced from a synthesized sorbitol‐based polyester polyol. Different formulations are developed with various blowing agent systems (chemical vs physical blowing). Synthetized foams are fully characterized and compared. The cell morphology is carefully investigated by tomography and scanning electron microscopy. The chemical nature of the primary compounds, foaming kinetics, density, thermal behavior, and conductivity are fully studied, with also the main transition materials temperatures. It is shown that blowing agents especially impact the foaming kinetics. In the case of chemically blowing foams, higher foaming rate and temperatures are obtained. The mechanical behavior is particularly analyzed using quasi‐static compression tests, according two main axes compared to the rise direction. A direct relationship is observed between the formulation, foam structure, foam morphology, and corresponding mechanical properties. Results clearly highlight unexpected properties of biobased PU foams with unveil anisotropic mechanical properties.     

Rigid polyurethane foams from a soybean oil-based Polyol

Polyurethane (PU) rigid foams were synthesized by substituting a polypropylene-based polyol with soybean oil-based polyol (SBOP). All the soy-based foams maintained a regular cell structure and had even smaller average cell size than the control foams. The density of soy-based foams was within 5% of the controls, except that the density of foams from 100% SBOP was 17% higher. Soy-based foams also had comparable initial thermal conductivity (k value) and closed cell content, higher T_g and compressive strength. However, while foams from 50% SBOP showed similar increase in k value to the 0% SBOP foams, under accelerated aging conditions, the 100% SBOP foams aged faster. Gas permeation tests performed on PU thin films showed higher N₂ permeation for PU thin films made from SBOP which is believed to be the cause of accelerated thermal aging.     

催化剂对废旧PU硬泡回收再利用的影响

用含有小分子醇的交联剂和催化剂使废旧聚氨酯（PU）硬泡进行降解能够获得多元醇，将降解料与聚醚多元醇、催化剂和发泡剂共混以制备白料，然后与黑料异氰酸酯混合均匀，得到再生PU硬泡。通过对降解产物的黏度、羟值以及获得的再生PU硬泡材料的密度、强度、吸水率、热稳定性、扫描电子显微镜、红外光谱和热失重等进行测试分析，得出了催化剂添加量对废旧PU材料回收再利用的影响因素。结果表明，催化剂（KOH）用量为0.9 g时废旧PU的降解效果最好，获得的再生PU硬泡的密度为37.6 kg/cm³，压缩强度为164.2 kPa，热导率为0.015 24 W/（m·K），吸水率为0.429 5 %。     

Development of water‐blown bio‐based thermoplastic polyurethane foams using bio‐derived chain extender

Water‐blown bio‐based thermoplastic polyurethane (TPU) formulations were developed to fulfill the requirements of the reactive rotational molding/foaming process. They were prepared using synthetic and bio‐based chain extenders. Foams were prepared by stirring polyether polyol (macrodiol), chain extender (diol), surfactant (silicone oil), chemical blowing agent (distilled water), catalyst, and diisocyanate. The concentration of chain extender, blowing agent, and surfactant were varied and their effects on foaming kinetics, physical, mechanical, and morphological properties of foams were investigated. Density, compressive strength, and modulus of foams decrease with increasing blowing agent concentration and increase with increasing chain extender concentration, but are not significantly affected by changes in surfactant concentration. The foam glass‐transition temperatures increase with increasing blowing agent and chain extender concentrations. The foam cell size slightly increases with increasing blowing agent content and decreases upon surfactant addition (without any dependence on concentration), whereas chain extender concentration has no effect on cell size. Bio‐based 1,3‐propanediol can be used successfully for the preparation TPU foams without sacrificing any properties. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Preparation and properties of rigid polyurethane foam based on modified castor oil

Castor oil polyol (COP) having a hydroxyl number of 400?mg?KOH/g was prepared through the transesterification reaction of castor oil with glycerol. The effect of reaction temperature on the composition, hydroxyl number and viscosity of the COP products was studied. A series of rigid polyurethane foams were synthesised using the mixtures comprising COP and a petroleum-based polyol with various proportions as polyol component. It was found that the foaming rate, compressive strength and dimensional stability and morphology of resulting foams were dominated by the foam formulation, in a more accurate way, COP content in the polyol mixtures. The combination of expandable graphite and dimethyl methyl phosphonate exhibited stronger flame retardant function which was ascribed to the synergistic effect associated with the simultaneous presence of the two additives. An improvement in thermal stability was observed due to the inclusion of the flame retardants.     

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.     

苯酐聚酯多元醇聚氨酯硬泡的阻燃性研究

以国产苯酐聚酯多元醇为主要原料制备了组合聚醚，再与多异氰酸酯反应，制备了阻燃型聚氨酯硬质泡沫。讨论了苯酐聚酯多元醇、硅油及发泡剂等因素对泡沫阻燃性的影响。结果表明，该组合聚醚与多异氰酸酯反应，制得的阻燃型聚氨酯硬质泡沫，其氧指数在28以上，压缩强度为300kPa，达到了国家标准GB／T8624-1997中B2级氧指数的要求。     

Improvement of thermal and mechanical properties by control of formulations in rigid polyurethane foams from polyols functionalized with graphene oxide

This article addresses the optimization of water-blown rigid polyurethane (RPU) foams obtained from a polyol functionalized with graphene oxide (GO). For this purpose, a series of RPU foams are herein synthesized by varying either the isocyanate index, the contents of catalyst or the contents of surfactant, or a combination of these three components. The modifications introduced in the formulation are based on the effect of GO on the reaction kinetics. These strategies are mainly focused on the increase of both isocyanate conversion and polymerization reaction, which decrease for the foams containing GO. Density, cellular structure, thermal conductivity, and mechanical properties of the resulting foams are herein investigated. The results show how controlling PU formulation allows to improve both the thermal and the mechanical behavior in these RPU foams containing GO. The highest cell size reduction of 25% and the lowest thermal conductivity are obtained for the sample with a simultaneous increase in isocyanate index, catalyst content, and surfactant content. Moreover, the adequate combination of these components leads to a high improvement of 59% of the relative Young's modulus and of 54% of the relative collapse stress. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47474.     

Porous polyurethane foams based on recycled poly(ethylene terephthalate) for oil sorption

In using recycled poly(ethylene terephthalate) (PET) as a petroleum sorbent we tried to achieve two important objectives simultaneously. PET waste was glycolized using trimethylolpropane (TMp) or pentaerytheritol (PEr) to produce suitable polyol oligomers for polyurethane (PU) foams. The glycolysis was carried out in the presence of manganese acetate as a catalyst under normal pressure in m‐cresol at 220 °C. Producing polyols, PEr degraded PET into lower molecular weights than TMp. So prepared oligomers were reacted with 2,4‐toluene diisocyanate providing several types of PU foam. The effect of various variables (polyol reactivity, water content, type of catalyst, isocyanate amount and surfactant) on the foam structure and properties were analyzed. Porosity of the PU foams was examined using environmental scanning electron microscopy. Foams based on glycolized TMp contain small uniform cells whereas other foams form less uniform cells with varying sizes including closed cells. Dynamic mechanical analysis gives much lower storage moduli for TMp‐based PUs that for those based on PEr, an effect of dangling ethylene chains in the former case. The glass transition temperatures T_g are higher when PEr rather than TMp is used. Our PU foams show good sorption properties and sufficient reusability. Copyright © 2012 Society of Chemical Industry     

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.     

Bio-based engineered nanocomposite foam with enhanced mechanical and thermal barrier properties

Bio-based polyurethane (PU) foams were developed from bio-polyol (castor oil-based) in the presence of selective catalyst, surfactant, and blowing agent. Bentonite nanoclay (NC) was incorporated into the bio-polyol mixture as nano-reinforcement, while, triethyl phosphate was used as flame-retardant agent. After fabrication, these bioengineered foam nano-composites were studied for microstructural, mechanical and thermal characterizations. Fourier transform infrared spectroscopy analysis indicated the presence of characteristic functionalities within biopolyol segments, which was influenced by reactant activity within the polyurethane (PU) foams. Scanning electron microscopy revealed the cellular morphology of the foam. Thermogravimetric analysis enabled the study of foam decomposition behavior for different sample compositions. Incorporation of NC into pristine foam was found to delay the onset degradation temperature. Flammability studies depicted significant enhancement of flame retardancy with incorporation of NC up to a certain loading level. Compression tests demonstrated that significant improvement of compressive strength properties of foams could be achieved by incorporating bentonite nanoclay, owing to nucleation effect of nanoclay and corresponding enhanced structural integrity. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47063.     

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.     

环戊烷发泡剂/组合聚醚体系的研究

通过相容性、自由发泡、模具发泡和流动性实验对环戊烷发泡剂/组合聚醚体系进行了研究。探讨了聚醚多元醇、催化剂和泡沫稳定剂对聚氨酯发泡体系性能的影响。结果表明:用环戊烷发泡剂/组合聚醚体系制备的聚氨酯泡沫流动性好成,本低泡,沫性能符合冰箱及冰柜指标要求。     

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     

Solvent-blown,rigid urethane foams from low cost castor oil-polyol mixtures

The preparation of solvent-blown rigid urethane foams from low cost castor oil-polyol mixtures was investigated. Solutions of triisopropanolamine, and of mixtures of triisopropanolamine and triethanolamine in castor oil, were used as the polyol component of these foams. Foams were prepared by reacting these polyol mixtures, in the presence of catalyst, surfactant, and trichlorofluoromethane, with prepolymers prepared from toluenediisocyanate and certain polyether polyols or mixtures of these polyether polyols with castor oil. The effect of polyol and prepolymer composition and blowing agent concentration on such foam properties as density and compressive strength was investigated. The properties of the castor oil-based foams were comparable to those of foams obtained from more costly polyols. Presented at the Spring Meeting of the American Oil Chemists' Society, St. Louis, Missouri, May 1–3, 1961. A laboratory of the Western Utilization Researchand Development Division, Agricultural Research Service, U. S. Department of Agriculture.     

Physical and mechanical properties of soy protein-based plastic foams

Flexible plastic foams using soy protein isolate (SPI), soy protein concentrate (SPC), and defatted soy flour (DFS) were produced by interacting proteins with glycerol-propylene oxide polyether triol (polyol), surfactant, triethanolamine (crosslinking agents), tertiary amine (catalyst), and water (blowing agent). The density, compressive stress, resilience, and dimensional stability of foams with SPI, SPC, and DFS increased as the initial concentration of soy protein increased. The foam density increased with increasing weight percentage of SPI, SPC, and DFS. The resilience values of SPI containing foam increased with the increasing addition of SPI up to a maximum 30% SPI addition. An increase in SPI up to 20% caused an increase in the compressive stress (225 kPa) in comparison to control polyurethane foam (187 kPa). The control foam and foam containing 20% DFS had a similar load-deformation relationship. The foam containing 20% SPI and SPC also exhibited a similar shape, but with a higher compressive stress. The compressive stress of all foams was steeply increased after 55% strain, since the foams completely collapsed upon compression.     

The effect of resin formulation on the cellular morphology and mechanical properties of phenolic foams

In the present study, the effects of blowing agent concentration, surfactant, and resin viscosity on the cellular structure, density, and compressive strength of phenolic foams were investigated. The mechanism of foaming was studied by thermal analyses, as well. The scanning electron microscopy was performed to investigate the morphology of foams. The presence of surfactant was essential to obtain a foam structure. By increasing the amount of blowing agent in the formulation, the bubbles became larger. The variation of the resin viscosity had the sharp effect on the cell size and its distribution so that the cell size dropped from 108 to 77 μm in the sample with the highest viscosity. The mechanical properties were significantly affected by foam structure as well as the cell uniformity. By decreasing the average cell sizes, the compression strength and modulus were improved up to more than 60%. Finally, the optimum values for viscosity of resin and, blowing agent, and surfactant concentrations were obtained. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48331.     

Improved dimensional stability of water-blown polyurethane foam with aluminum hydroxide and magnesium hydroxide

Water is eco-friendly and safe; thus, it used as a blowing agent in the fabrication of water-blown polyurethane (PU) foam. However, water-blown PU foam may experience dimensional instability due to shrinkage of the cells inside the foam. In order to reduce cell shrinkage due to the loss of CO₂ gas, vacuum formation is prevented in the closed-cell foam and the maximum reaction temperature must be raised to increase the degree of curing of the PU foam. In this study, two flame retardants, aluminum trihydrate (ATH) and magnesium dihydrate (MDH), were selected as additives to partially open the cells and increase the maximum reaction temperature. ATH and MDH were both effective for increasing the maximum foam reaction temperature and decreasing dimensional change. Notably, PU foams with 7.5 wt% ATH were the most dimensionally stable at both room temperature and high temperature. Moreover, the compressive strength and flexural strength of such foams were also improved compared to those of the foams without any additive.     

Novel preparation and mechanical properties of rigid polyurethane foam/organoclay nanocomposites

A novel method for preparing rigid polyurethane (PU) foam/organoclay nanocomposites was developed through the direct incorporation of an organoclay into PU foam matrices without the addition of any physical or chemical blowing agent. The resultant foams with an appropriate content of the organoclay had a finer cell structure than the pristine PU foams because the organoclay not only acted as a nucleating agent as expected but also acted as a blowing agent of the PU foams; this could be attributed to the bound water between the interlayers of the organoclay. In addition, the incorporation of the organoclay up to 4 phr resulted in improvements in the tensile and compressive strengths, with the maximum values appearing at 2 phr (110 and 152%, respectively). The significant improvement in the mechanical properties could be attributed to the finer cell structure and the increased internal strength of the materials due to the higher degree of hydrogen bonding. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007