Polyether-based Polyurethane Research Articles

Chlorine degradation of polyether-based polyurethane

The tensile properties of polyether-based polyurethane (PU) filaments decrease with increasing chlorine concentrations as well as with treatment times. Fourier transform infrared (FTIR) results show the formation of quinoid, azo, and aldehyde groups in the chlorine-treated PU, and increased hydrogen bonding between the COC in the soft segment and the NH in the hard segments. A breakdown mechanism involving chain cleavages along the ether linkages in the soft segments as well as at the urethane linkages of the hard–soft segment interfaces is proposed. Chlorine-treated PU showed increased solubility in tetrahydrofuran (THF). The molecular weight data of the THF-soluble portion of treated PU also support the proposed locations of chain scissions. The increased soft segment Tg and Tm with increasing chlorine concentrations are results of increased phase-mixing and hydrogen bonding. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 3263–3273, 1997

Porcine oocytes produce CEEF only during their growth period and transition to metaphase I

In this study, the effect of the structure of polyether-based polyurethane (PU) membranes on their gas separation properties has been investigated. In this regard, a series of polyurethanes based on hexamethylene diisocyanate (HDI) and 1,4-butanediol as hard segments and different soft segments such as poly(tetramethylene glycol) (PTMG, 2000 g/mol), poly(ethylene glycol) (PEG, 2000 g/mol) and PTMG/PEG mixture were synthesized. PU membranes were prepared by thermal phase inversion method and their physical properties were analyzed by FT-IR, XRD and DSC analyses. The obtained results from FT-IR and DSC analyses indicated that the phase separation of hard and soft segments decreased and chain mobility was restricted, resulting in the increase in glass-transition temperature of the soft segment, by content of the PEG in the PU structure. The permeability of pure N2, O2, CH4 and CO2 gases were determined using constant pressure method at different feed pressures and temperatures. The results of gas permeation experiments showed that by increasing the ether group content in the polymer structure, permeability of the pure gases decreased, while CO2/N2 ideal selectivity increased. The obtained results also indicated that the permeability of CO2 decrease from 132.52 barrer in PU0 (PU containing 100 wt% of PTMG in soft segment) to 20 barrer in PU100 (the PU containing 100 wt% of PEG in soft segment), respectively. CO2/N2 selectivity increased from 28 to 90. Trade-off evaluation also showed that the potential of studied membranes for commercialization in CO2/N2 and even CO2/CH4 separations increase by PEG content in polymer and the PU membrane which contains 75/25 wt% ratio of PEG/PTMG had the highest.

Assessment of resistance of non-metallic coatings to silt abrasion and cavitation erosion in a rotating disk test rig

Hydraulic damage tests have been carried out on five types of non-metallic coating materials in slurry water. A rotating disk test rig was used to simulate silt abrasion and cavitation erosion with natural silt at periphery speeds of 30 and 40 m s −1. The resistances of the various coatings to silt abrasion, and the combination of abrasion and cavitation, have been measured and compared under specified hydraulic conditions. The tests show that among the five selected materials, epoxy resin reinforced by synthetic corundum particles and castable polyether-based polyurethane rubber were the most resistant coatings to abrasion and the combined abrasion-cavitation damage, respectively. It has also been found that of the materials tested, high elasticity polyurethane had the greatest resistance to cavitation, whilst a brittle material, epoxy resin, had the least in high-silt-content water. The erosion rates of the coatings examined were generally proportional to the peripheral speed of the disk raised to the power of 3.1–4.5 under the given conditions. The synergistic effect of cavitation and abrasion on different coating materials has been discussed.

Transport of iron halides through polyurethane ether-type membranes

The transport of iron(III) using polyether-based polyurethane membranes was studied. The rate at which iron passes through the membrane depends on the formation of the HFeX 4 species, which is related to the initial acid and salt concentration of the metal solution. Iron is quantitatively transported from a cell of high acid-halide concentration to one with low concentration.

The sorption behaviour and separation of some metal thiocyanate complexes on polyether-based polyurethane foam

The preliminary screening tests on the preconcentration of lanthanum(III), aluminium(III), molybdenum(VI), gallium(III) and tungsten(VI) thiocyanate complexes in aqueous media by unloaded foam indicated a reasonable percentage of metal ions were retained on the foam. The influence of various parameters affecting the retention of these complex species from the aqueous media by the foam were critically studied and the possible mechanisms of the sorption of the compounds were suggested. However, owing to the complex chemical nature of the polyether—polyurethane foam, several mechanisms may be involved simultaneously. Attempts for the quantitative retention and recovery of the tested complexes by the foam columns were also made and satisfactory results were obtained. The height equivalent to theoretical plates (HETP) of the foam columns were calculated from the chromatograms and break through capacity curve and were found in the range 1.8–2.3 mm at flow rates up to 15 cm 3/min. The proposed foam column method has been successfully used for the separation of a series of complex mixtures of the tested metal thiocyanate complexes in aqueous media. The membrane properties of the foam sorbents offer unique advantages over conventional bulk type granular sorbents in rapid, versatile effective separations and preconcentrations of different complexes from fluid samples.

Extraction Kinetics of Uranium(VI) with Polyurethane Foam.

The extraction kinetics of uranium(VI) from aqueous nitrate solution with polyether-based polyurethane foam was investigated in a batch reactor with automatic squeezing. The extraction curves of uranium(VI) concentration in solution vs. extraction time exhibited a rather rapid exponential decay within the first few minutes, followed by a slower exponential decay during the remaining period. This phenomenon can be attributed to the presence of two-phase structure, hard segment domains and soft segment matrix in the polyurethane foam. A two-stage rate model expressed by a superposition of two exponential curves was proposed, according to which the experimental data were fitted by an optimization method. The extraction rate of uranium(VI) was also found to increase with increasing temperature, nitrate concentration, and hydration of the cation of nitrate salt.

Extraction Behavior of Uranium(VI) with Polyurethane Foam

Abstract The extraction of uranium(VI) from aqueous solution with polyether-based polyurethane (PU) foam was studied. The effects of the kinds and concentrations of nitrate salts, uranium(VI) concentration, temperature, nitric acid concentration, pH, the content of poly(ethylene oxide) in the polyurethane foam, and the ratio of PU foam weight and solution volume on the extraction of uranium(VI) were investigated. The interferences of fluoride and carbonate ions on the extraction of uranium(VI) were also examined, and methods to overcome both interferences were suggested. It was found that no uranium was extracted in the absence of a nitrate salting-out agent, and the extraction behaviors of uranium(VI) with polyurethane foam could be explained in terms of an etherlike solvent extraction mechanism. In addition, the percentage extraction of a multiple stage was also estimated theoretically.

Spectrophotometric determination of vanadium in glass and ceramics after extraction of the vanadium—salicylhydroxamic acid complex on polyurethane foam

A simple spectrophotomeric method was developed for the determination of traces of vanadium present in glass and ceramic raw materials. The method involves the formation of a vanadium-salicylhydroxamic acid complex in 1 M HF-H 2SO 4 medium, followed by extraction of polyether-based polyurethane foam and elution of the complex with acidified acetone (9.5 ml of acetone + 0.5 ml of 1 M HCl) for spectrophotomeric measurement at 520 nm. The method obeys Beer's law from 0.5 to μg V ml −1. The molar absorptivity was calculated to be 6.9 x 10 3 mol 1 −1 cm −1 at 520 nm. Interferences from other metals, viz., Fe, Co, Mo, Zr, Hf and Ti, were eliminated by using HF medium. The method was applied to several glass and ceramic samples.

Polyisobutylene‐based urethane foams. II. Synthesis and properties of novel polyisobutylene‐based flexible polyurethane foams

AbstractNovel polyisobutylene‐based flexible polyurethane foams (PIB–PUF) have been prepared manually by the prepolymer method using three‐arm star hydroxyl‐terminated polyisobutylenes (PIB–triols) and toluene diisocyanate (TDI). Solvent extraction and IR spectroscopy of PIB–PUFs indicated essentially complete crosslinking. Conventional polyether‐based polyrethane foams (PE–PUFs) and polybutadiene‐based polyurethane foams (PBD–PUFs) have also been prepared by the same method and select physical‐mechanical properties of all these urethane foams, such as tensile strength, elongation, resilience, water permeability, hot air stability, and hydrolytic stability, have been examined and compared. Although the density of PIB–PUF is lower than that of PE–PUF, its tensile strength is superior to the latter. Elongation of PIB–PUF is almost the same as those of the other foams. The PIB–PUF exhibits low resilience which indicates good damping properties. Due to the hydrophobicity of the soft segment, PIB–PUF exhibits very low water permeability. The hydrolytic and hot air stability of PIB–PUFs are outstanding. Attempts have been made to determine gas permeabilities; however, due to the open‐cell nature of the foams, these studies could not be completed. The new PIB‐based urethane foams combine excellent thermal, environmental, barrier, and mechanical properties, unmatched by conventional PUFs.

Fine colloidal silica as reinforcing filler in polyurethane polymers

Colloidal silica in the particle size range 1.4–10 nm was extracted in to tetrahydrofuran (THF). Alkali silicate solutions with SiO2 : M2O (M = Li, Na, K, Cs) ratios ranging from 3:1 to 20:1 were used as source of silica particles in the size range 1.4–4.4 nm whereas commercial silica sols were used for particles in the range 5–10 nm. Films of polyester- and polyether-based polyurethane-containing colloidal silica were prepared and their mechanical properties measured. The reinforcing effect increased with increasing silica content and showed a maximum between 1.5 and 2.5 nm for polyether-based polyurethane and between 4 and 6 nm for polyester-based polyurethane. The area under the hysteresis loops of the stress–strain curves also showed maximum in the same particle size ranges for the two types of polyurethane. Reinforcement mechanisms are discussed in terms of interactions between small particles and hard or soft segments of the polymer chains.

Extraction of Mo, W and Tc with polyurethane foam and with cyclic polyether from SCN −/HCL medium

The extraction of molybdenum, tungsten and technetium by polyether-based polyurethane foam and by a cyclic polyether from aqueous thiocyanate solutions is described. The influence of the reductants stannous chloride and ascorbic acid has also been studied. The possibilities of the polyurethane foam for preconcentration and determination of molybdenum are discussed.

DSC annealing study of microphase separation and multiple endothermic behavior in polyether-based polyurethane block copolymers

Copolymeres segmentes a base de polyoxypropylene contenant 30,4% en poids d'oxyde d'ethylene

Simultaneous SAXS-DSC study of multiple endothermic behavior in polyether-based polyurethane block copolymers

Simultaneous SAXS-DSC study of multiple endothermic behavior in polyether-based polyurethane block copolymers

Chromatographic analysis of thermoplastic, medical-grade, polyether-based polyurethane elastomers

An analytical procedure is described for rapid qualitative analysis of medical-grade polyether-based polyurethane elastomers. The elastomers are conventionally the complex reaction product of an isocyanate-terminated linear polyether prepolymer with either a diamine or a diol chain extender. The polymer is cleaved into the corresponding diamine, polyether, diol, or hydrocarbon by molten alkali fusion at high temperature. These fragments are analysed by gas and gel-permeation chromatography, after separation by a liquid—liquid extraction procedure. Polyethers are further cleaved into the corresponding polyol acetates by using a mixed anhydride reagent, before gas chromatographic analysis.

Studies on the extraction of phosphomolybdate by polyether foam

To establish the mechanism of heteropoly anion extraction, the sorption of phosphomolybdate by polyether-based polyurethane foam was investigated. The effect of several variables on the extraction was studied and the optimum conditions were ascertained. The results of this study indicate that the cation-chelation mechanism cannot account for the extraction of phosphomolybdate by polyether foam.

Extraction of monovalent and divalent cations by polyether-based polyurethane foam

The extraction of silver(I), thallium(I), barium(II), and lead(II) ions by polyester-based polyurethane foam from aqueous solution is described. The extraction equilibrium constants and the ion-pair formation constants for the picrate systems containing the four ions are reported. The sorption of these ion-pairs by polyether foam can be explained in terms of cation chelation.

Effect of molecular weight distribution of poly(oxytetramethylene)glycol on cut growth resistance of polyurethane

A new method is proposed to improve the cut growth resistance of polyether-based polyurethane elastomers, i.e., polyethers used in this method are characterized by a double-humped distribution of molecular weight (DHDM), prepared by blending low-molecular-weight components and high-molecular-weight ones. The measurements of stress–strain curves, viscoelastic properties, and DSC thermograms of polyurethane elastomers before and after fatigue tests indicate that the destruction of the super molecular structure because of fatigue is smaller in the elastomer by our method, while in the conventional elastomer it is greatly destructed to change into fibrous structure. Further, the broad line NMR measurements show that the molecular motion of DHDM-type elastomers is more active, which is considered to contribute to the improved cut growth resistance of the elastomers.