Polyurethanes from benzene polyols synthesized from vegetable oils: Dependence of physical properties on structure

Asymmetric and symmetric aromatic triol isomers were synthesized from erucic acid. The pure asymmetric and symmetric triols were crosslinked with MDI into their corresponding polyurethane sheets. The physico‐chemical properties of these polyurethanes were studied by Fourier transform infrared (FTIR) spectroscopy, X‐ray diffraction (XRD), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), thermogravimetric analysis coupled with Fourier transform infrared (TGA‐FTIR) spectroscopy, and tensile analysis. The A‐PU and S‐PU demonstrated differences in their glass transition temperatures (T_g) and crosslinking densities. The difference in T_g of these polyurethanes could be explained by the differences in crosslinking densities, which could be related to the increase in steric hindrance, to the crosslinking MDI molecules, between adjacent hydroxyl groups of the asymmetric triol monomers. Overall, it was found that both polyurethanes had similar mechanical and thermal properties. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

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 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     

Rigid polyurethane foams made from high viscosity soy‐polyols

This study investigated the physical properties of water‐blown rigid polyurethane (PU) foams made from VORANOL®490 (petroleum‐based polyether polyol) mixed with 0–50% high viscosity (13,000–31,000 cP at 22°C) soy‐polyols. The density of these foams decreased as the soy‐polyol percentage increased. The compressive strength decreased, decreased and then increased, or remained unchanged and then increased with increasing soy‐polyol percentage depending on the viscosity of the soy‐polyol. Foams made from high viscosity (21,000–31,000 cP) soy‐polyols exhibited similar or superior density‐compressive strength properties to the control foam made from 100% VORNAOL® 490. The thermal conductivity of foams containing soy‐polyols was slightly higher than the control foam. The maximal foaming temperatures of foams slightly decreased with increasing soy‐polyol percentage. Micrographs of foams showed that they had many cells in the shape of sphere or polyhedra. With increasing soy‐polyol percentage, the cell size decreased, and the cell number increased. Based on the analysis of isocyanate content and compressive strength of foams, it was concluded that rigid PU foams could be made by replacing 50% petroleum‐based polyol with a high viscosity soy‐polyol resulting in a 30% reduction in the isocyanate content. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

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.     

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     

Fabrication,characterization and low‐velocity impact testing of hybrid sandwich composites with polyurethane/layered silicate foam cores

A series of nanophased hybrid sandwich composites based on polyurethane/montmorillonite (PU/MMT) has been fabricated and characterized. Polyaddition reaction of the polyol premix with 4,4′‐diphenylmethane diisocyanate was applied to obtain nanophased PU foams, which were then used for fabrication of sandwich panels. It has been found that the incorporation of MMT resulted in higher number of PU cells with smaller dimensions and higher anisotropy index (cross sections RI and RII). The obtained materials exhibited improved parameters in terms of thermal insulation properties. The results also show that nanophased sandwich structures are capable of withstanding higher peak loads than those made of neat PU foam cores when subject to low‐velocity impact despite their lower density than that of neat PU foams. This is especially significant for multi‐impact recurrences within the threshold loads and energies studied. POLYM. COMPOS., 2011. © 2010 Society of Plastics Engineers     

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.     

Thermo‐responsive polyurethane hydrogels based on poly(ethylene glycol) and poly(caprolactone): Physico‐chemical and mechanical properties

In this work, we present the synthesis and characterization of chemically crosslinked polyurethanes (PU) composed of poly(ethylene glycol) (PEG) and poly(caprolactone) diol (PCL‐diol), as hydrophilic and hydrophobic segments respectively, poly(caprolactone) triol (PCL‐triol), to induce hydrolysable crosslinks, and hexamethylene diisocyanate (HDI). The syntheses were performed at 45 °C, resulting in polyurethanes with different PEG/PCL‐diol/PCL‐triol mass fractions. All the PUs are able to crystallize and their thermal properties depend on the global composition. The water uptake capacities of the PU increase as the PEG amount increases. The water into hydrogels is present in different environments, as bounded, bulk and free water. The PU hydrogels are thermo‐responsive, presenting a negative dependence of the water uptake with the temperature for PEG rich networks, which gradually changes to a positive behavior as the amount of poly(caprolactone) (PCL) segments increases. However, the water uptake capacity changes continuously without an abrupt transition. Scanning electron microscopy (SEM) analyses of the hydrogel morphology after lyophilization revealed a porous structure. Mechanical compression tests revealed that the hydrogels present good resilience and low recovery hysteresis when they are subject to cycles of compression–decompression. In addition, the mechanical properties of the hydrogels varies with the composition and crosslinking density, and therefore with the water uptake capacity. The PU properties can be tuned to fit for different applications, such as biomedical applications. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43573.     

Mechanical properties of BaTiO3 open-porosity foams

Barium titanate (BaTiO₃) foams synthesized via direct foaming method using silicon-free, rigid polyurethane systems (PU), commercially purchased and lab developed, are being engineered for piezocomposites in sonar applications. The mechanical properties of these foams were measured using confined compression testing to evaluate the suitability of these foams for the intended application. Compressive modulus and collapse strain determined from the experimental data increased with increasing density. Additionally, the foams fabricated using the lab developed PU (LPU) showed a higher mechanical strength due to a higher average density than the foams developed using commercial PU (CPU) system. The data was then fit with a phenomenological model to verify the values of the compressive properties extracted from the experimental data and also to extract additional properties such as tensile strength. Based on these findings, it is proposed that these foams can be successfully incorporated into piezocomposites by infiltrating the foams with polymer.     

Preparation and properties of novel poly(propylene oxide)‐block‐polylactide‐based polyurethane foams

A novel degradable flexible polyurethane (PU) foam was prepared by varying the ratio of poly(propylene oxide) (PPO) and triarm poly(propylene oxide)‐block‐polylactide copolymer (PPO‐b‐PLA), and was compared with conventional PU foams based on toluene diisocyanate (TDI) and PPO. Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC) showed that introducing PLA segments were able to result in a transition from a microphase separated state to a microphase mixed state and improve the microphase mixing. The changes in structure and domain size distribution associated with this transition were found to have led to enhanced mechanical properties such as the tensile strength, the elongation at break, and the rebound resilience for the PU foams containing PLA segments. Furthermore, it was observed that the network structure was destroyed by hydrolytic degradation in alkali solution (10 wt%/vol%) at 80°C for 50 h, and that as the PLA content increased, the degradation rate of PU foams enhanced. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers     

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     

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     

Physicomechanical,friction, and abrasion properties of EVA/PU blend foams foamed by supercritical nitrogen

Elastomer foams based on EVA, PU, and EVA/PU blends formulated for shoe‐sole applications were prepared by a supercritical N₂ batch foaming process and characterized for physicomechanical, friction and abrasion properties. The blending of EVA with PU was aimed for improving the friction and wear characteristics of the EVA based foams. All of the foams prepared showed spherical cells with closed‐cell morphology and the cell sizes varied with varying the EVA/PU blend ratio and CaCO₃ content of the foams. The properties such as hardness and resilience, friction coefficients and abrasion resistance improved for the EVA/PU blend foams compared to the EVA foam, but their compression set, tensile strength, and tear strength were inferior to the EVA foam. The incorporation of CaCO₃ filler increased density, hardness, tensile strength, and tear strength of the EVA/PU blend foams but decreased resilience, compression set, friction coefficients, and abrasion resistance. The improvement in friction coefficients and wear resistance obtained in the EVA/PU blend foams was significant for shoe‐sole applications. POLYM. ENG. SCI., 2017. © 2017 Society of Plastics Engineers     

Processing and properties of an ethylene–vinyl acetate blend foam incorporating ethylene–vinyl acetate and polyurethane waste foams

Waste polyurethane foam (w‐PU) and waste ethylene–vinyl acetate foam (w‐EVA) were used as fillers for the production of an ethylene–vinyl acetate (EVA) blend foam. Two different foaming techniques (single‐stage and heat–chill processes) were used for this purpose. The waste foam concentration was varied up to 30 wt % of the original EVA. The physical, mechanical, and morphological properties of the filled foam were studied. The single‐stage process produced blend foams with a lower density and a greater cell size than the foams obtained by the heat–chill process. The density and compression strength of the blend foam increased as the percentage of w‐PU foam increased. However, for the w‐EVA/EVA blend foams, the addition of w‐EVA foam did not significantly affect the density or compression strength compared to the original EVA foams. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44708.     

Morphology and tensile properties of crosslinked nanocomposite foams of low‐density polyethylene and poly(ethylene‐co‐vinyl acetate) blends

This paper studies the morphology and tensile properties of nanocomposite foams of blends of low‐density polyethylene (LDPE) and poly(ethylene‐co‐vinyl acetate) (EVA). Preparations of LDPE/EVA nanocomposites were conducted in an internal mixer, and then samples were foamed via a batch foaming method. Morphology of the nanocomposite blends and nanocomposite foams was studied by X‐ray diffraction, transmission electron microscopy, and scanning electron microscopy. Morphological observations showed that nanoparticle dispersion in the polymeric matrix was affected by the blend ratio in a way such that EVA‐rich samples had a better dispersion of nanoclay than LDPE‐rich ones. In addition, the tensile properties of the nanocomposite foams were related to different variables such as blend ratio, clay content, and foam density. J. VINYL ADDIT. TECHNOL., 2010. © 2010 Society of Plastics Engineers     

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.     

Hexamethoxycyclotriphosphazene as a flame retardant for polyurethane foams

Polyurethane (PU) foams were protected by phosphorous and nitrogen‐based molecular flame retardant hexamethoxycyclotriphosphazene c‐[N = P(OMe)₂]₃ (HMCPT). This compound was synthesized, analyzed, and investigated with respect to its thermal behavior, compatibility, and efficiency as a flame retardant (FR) for PU foams. The decomposition of HMCPT starts at 186 °C in air and under argon, as indicated by TG/DSC measurements. It was possible to introduce 5 per hundred parts polyol (phpp) of HMCPT into the PU foams. The mechanical and morphological characteristics of the protected foams—compression load deflection, tenacity, tensile elongation, air perviousness, and raw density—were investigated indicating that the FR has an impact on all of these properties. The flame retardancy was evaluated with the FM VSS 302 test, where an self‐extinguishing classification was reached with 5 phpp of HMCPT. Cone calorimeter measurements provide evidence for a flame poisoning mechanism. Copyright © 2013 John Wiley & Sons, Ltd.     

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.     

Chemical recycling of reinforced polyurethane from the automotive industry

R-RIM PU (reinforced-reaction injection molding polyurethanes) from the automotive industry (production scrap and parts at the end of their life cycle) can be recycled for the production of new RIM PU by a chemical process. Among the various possible chemical processes (hydrolysis, alcoholysis, aminolysis, and pyrolysis), we have examined glycolysis, a particular form of alcoholysis, for the purpose of obtaining a mixture of oligomers sufficiently similar to a polyol to be used in the production of new R-RIM PU. Glycolysis with dipropylene glycol (DPG) of R-RIM PU forms a monophasic product that could be used in the preparation of new, highly crosslinked polymers, similar to those used in the preparation of rigid thermal insulation foams. The same product, because of its high hydroxyl number, cannot be directly re-used in the production of new RIM PU. Partial substitution of free DPG in the glycolysis product with a triol having high molecular weight forms a homogeneous mixture suitable for production of new RIM PU. This final product has been used in the original R-RIM application introducing an appropriate optimization of formulation. In comparison with RIM PU obtained from only virgin materials, the loss in properties of molded parts based on even high amounts of regenerated polyol was only marginal.