Extraction of aurocyanide ion-pairs by poly(oxyethylene) extractants

Aurocyanide ion-pairs with alkali-metal ions are extracted efficiently into organic phases with the aid of long-chain polyethers. The results of distribution experiments can be rationalized by molecular mechanics calculations. The polyether is shown to co-ordinate to the alkali-metal cation through the ether oxygen atoms, wrapping around the cation in a helical configuration. High extraction efficiencies are obtained with high dielectric-constant solvents, which tend to stabilize the helical polyether-cation complex. The preferential secondary solvation of the aurocyanide anion by the chosen solvents also has an important influence on the extraction efficiency.     

Mechanical properties of polyurethane foams modified by polymer-polyols

The mechanical properties of polyurethane foams based on tolylene diisocyanate and polyether modified by polymer-polyol, which is a styrene-acrylonitrile copolymer grafted onto polyol, were studied. The breaking stress, the hardness at 40% compression, the elongation at break, and the density depend on the amount of both the hard phase in the polymer-polyol and the polymer-polyol component in the polyurethane foam composition. Samples with a density of ～30 kg/m³ were prepared to have other mechanical properties practically identical to those of standard samples with a density of ～37–47 kg/m³.     

Epoxy modified polyurethane rigid foams

Rigid IPN foams were prepared by sequential polymerization of polyurethane and epoxy systems. Significantly higher compressive modulus and strength were observed with the IPN foams in comparison to the corresponding polyurethane rigid foams. The IPN foams show one glass transition temperature. The single T_g indicates the very small domain size in the PU-epoxy IPN's.     

Thermal behaviour of rigid polyurethane foams

The effects of P- and Cl-containing reactive antipyrenes with different compositions and structures on the mechanism and kinetics of the total thermal decomposition of rigid polyurethane foams, together with the possibility of evaluating their effectiveness as combustion inhibitors, were studied by means of a combined thermal analysis technique. It is shown that dynamic thermal analysis can register the changes resulting in the mechanisms and kinetics of the thermal decompositions of the investigated polyurethanes from comparatively low concentrations and differences in the concentrations and from differences in the chemical compositions and structures of the antipyrenes. The most sensitive characteristics associated with the influence of antipyrenes in this case were the coke residue determined at 850? in an inert medium and the areas of exothermic peaks I and II in the DTA curve in air medium.     

Preconcentration of strontium on polyurethane foams

A method for the preconcenration of strontium on loaded and unloaded polyurethane foams is described. Parameters affecting the extraction of metal ion, such as pH, reagent concentration and background medium have been investigated. The method can be applied to preconcentrate strontium from aqueous samples.     

Thermal behaviour of rigid polyurethane foams

By means of a combined thermal analysis technique, the thermal behaviour of rigid polyurethane foams containing additive antipyrenes was studied. The presence of phosphorus- and phosphorus/chlorine-containing antipyrenes based on phosphate and phosphonate and a combination of them led to decreases in the rates of heat and weight loss during heating. More steps of decomposition were formed and the interval of decomposition was widened and shifted to higher temperatures. Some thermal characteristics make it possible to predict the optimum antipyrene compositions and concentrations with minimum time, labour and material consumption under laboratory conditions.

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Zusammenfassung Mittels einer kombinierten Technik wurde das thermische Verhalten eines starren, Antipyrene als Additiv enthaltenden Polyurethanschaumes untersucht. Phosphor und Phosphor/Chlor enthaltende Antipyrene auf Phosphat- und Phosphonatbasis und eine Kombination dieser Substanzen vermindern die Geschwindigkeit der Wärmeentwicklung und des Gewichtsverlustes während des Aufheizvorganges. Es treten mehr Zersetzungsschritte auf und das Temperaturintervall der Zersetzung ist größer und nach höheren Temperaturen hin verschoben. Einige thermische Kennwerte ermöglichen die Voraussage der optimalen Zusammensetzung und Konzentration des Antipyren-Additivs für minimalen Zeit-, Arbeits- und Materialaufwand unter Laboratoriumsbedingungen.

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Thermal properties of lignin-and molasses-based polyurethane foams

Lignin-and molasses-based polyurethane (PU) foams with various lignin/molasses mixing ratios were prepared. The hydroxyl group in molasses and lignin is used as the reaction site and PU foams with various isocyanate (NCO)/the hydroxyl group (OH) ratios were obtained. Thermal properties of PU foams were investigated by differential scanning calorimetry (DSC), thermogravimetry (TG) and thermal conductivity measurement. Glass transition temperature (T _g) was observed depending on NCO/OH ratio in a temperature range from ca. 80 to 120°C and thermal decomposition temperature (T _d) from ca. 280 to 295°C. Mixing ratio of molasses and lignin polyol scarcely affected the T _g and T _d. Thermal conductivity of PU foams was in a range from 0.030 to 0.040 Wm⁻¹ K⁻¹ depending on mixing ratio of lignin and molasses.     

New polyurethane foams modified with cellulose derivatives

New polyurethane foams were elaborated with different cellulose derivatives as raw material, by the one-shot process. The foams were submitted to soxhlet extraction in order to quantify the amount of cellulose derivative incorporated in the foam by chemical bonding. The foams were characterized by means of FTIR, solid state ¹³C NMR spectroscopy, thermogravimetric analysis, differential scanning calorimetry, scanning electron microscopy and dynamic mechanical analysis (DMA). The FTIR- and solid state ¹³C NMR showed characteristic peaks for cellulose derivatives and polyurethane. DMA measurements indicated that storage modulus increased with increasing content of cellulose derivatives. The highest value was obtained for foams prepared with cellulose sulphate.     

N-Aryltetramethylguanidines,living catalysts for polyurethane foams

N-Aryltetramethylguanidines catalyze the formation of polyurethane foams by a novel exchange reaction involving C?N double bond of the guanidines and the isocyanate groups of the polyisocyanates. The catalyst sites are transferred to the growing polymer network, achieving a rapid catalytic build-up of the foam.     

Extraction of azo dyes by polyurethane foam

The extraction of 12 closely related mono-azo dyes by polyester and polyether-type polyurethane foams was studied to gain more information regarding the mechanism of the extraction of organic compounds. The effects on extraction of solution pH, dye concentration and salt concentration were investigated. It was found that the extraction of the dyes involved a neutral zwitterionic species and is highly dependent on the parameters studied. The dependency of the extraction on these parameters can be explained in a manner consistent with solvent extraction; however, the dual-mode sorption mechanism seems a more likely model. This mechanism involves both absorption related to solvent extraction, and an added component for surface adsorption. While the dual-mode sorption model explains the observed extraction behaviour, the data suggest that surface adsorption plays a much larger role than previously considered.     

单宁聚氨酯土壤微生物降解研究

采用凝胶渗透色谱仪(GPC)、傅立叶变换红外光谱仪(FT-IR)和电子扫描显微镜(SEM)等实验手段,考察了单宁聚氨酯(WT-PU)在土壤微生物降解前后的化学结构与微观形态的变化,而作为比较用的模型化合物(TMP-PU)在同样的条件下几乎没有变化。结果表明单宁一这交联点在PU整体中以无规降解的方式优先降解,在整个降解过程中,不仅伴随着PU硬段的氢键减弱,软段的氢键也同样有相当的减弱。     

Extraction behavior of ion-pairs of azo-dye cations and their analytical applications

The extraction of ion-pairs of monovalent organic acid anions and inorganic anions with 4-(4-diethylaminophenylazo)-N-alkylpyridinium cation (azo-dye cation) is described. The alkyl groups studied were methyl, ethyl, propyl, butyl and benzyl groups. The ion association, distribution and extraction constants for the ion-pairs were determined from partition equilibrium studies. These azo-dye cations can extract chelate anions containing sulfonic acid groups into chloroform. The cobalt complex of 2-nitroso-1-naphthol-4-sulfonic acid is extracted quantitatively into chloroform with the propyl derivative as a 1:3 Co: dye complex; measurement of the absorbance of the extracted ion-pair provides a very sensitive determination of cobalt, the apparent molar absorptivity in chloroform being 1.66 × 10⁵ l mol^-1 cm^-1 at 566 nm. The methyl derivative is suitable for cation extraction of monovalent anions such as the complex nickel anion of 4-chloro-2-nitroso-1-naphthol, and anionic surfactants. The possibilities for application of these azo-dye cations in extraction-spectrophotometric determinations are very large.     

Extraction of aromatic organic compounds by polyurethane foam

The mechanism of extraction of organic compounds by open-cell polyurethane foam has been investigated through a detailed study with simple aromatic compounds. Comparison with identical extractions into diethyl ether suggests that the basic extraction mechanism is an ether-like solvent extraction process. The addition of salt increases the extraction and changing the dielectric constant of the aqueous solution also affects the extraction. For organic compounds which have a group capable of hydrogen bonding, some additional factor appears to influence the extraction. This appears to be hydrogen bonding with the polyurethane foam; it is stronger with polyether foam and reduced by the presence of a strong intramolecular hydrogen-bonding group placed ortho to the hydrogen-bonding group. Thermodynamic studies support these conclusions.     

Tensile deformation behaviour of the polymer phase of flexible polyurethane foams and polyurethane elastomers

The change in micromorphology of the polymer phase (single strut) of a flexible polyurethane foam during deformation has been investigated by attenuated total reflection infrared spectroscopy - linear dichroism and by atomic force microscopy. Deformation and, therefore, orientation take place mainly in the soft rubbery phase. This two-phase elastic deformation process has been translated into a mathematical model, which correctly predicts the shape of a single-strut stress-strain curve. The theory also predicts the ultimate shape of stress-strain curves of polyurethane elastomers at various hard phase contents and of low-density polyethylene at various temperatures. Deviations from the elastic behaviour could be ascribed to yielding in combination with the rubbery behaviour.     

Glass transition temperature of polyurethane foams derived from lignin by controlled reaction rate

Sodium ligninosulfonate (LS)-based polyurethane (PU) foams were prepared using three kinds of ethylene glycols, diethylene glycol, triethylene glycol or polyethylene glycol. Two kinds of industrial NaLS, acid-based and alkaline-based NaLS, were mixed with various ratios, and foaming reactions were controlled. Mixing, cream, and rise time were used as an index of foaming reaction. Mixing time was defined as the time interval from adding isocyanate to detection of evolved heat under stirring, cream time as the time interval from termination of stirring to starting of foaming, and rise time as the time interval from starting to completion of foaming. The above reaction time increased with increasing amount of acid base NaLS content in polyols. Apparent density, compression strength and compression modulus of PU foams linearly increased with reaction time. Thermal decomposition temperature was measured by thermogravimetry and glass transition temperature by differential scanning calorimetry. Glass transition temperature can be controlled in a temperature range from 310 to 390 K by changing the mixing rate of two kinds of LS and molecular mass of ethylene glycols. It was found that mechanical and thermal properties of PU foams are controllable through the foaming reaction rate using two kinds of industrial lignin.     

Extraction of tin by the use of polyurethane foam

Three types of polyurethane foam were tested for the extraction of tin by static and flow systems. The amount of tin extracted varied with the type of foam, acid strength, and chloride and metal-ion concentrations. Quantitative extraction and recovery could be achieved. Open-cell polyurethane foam sponge is thought to act as a "solid solvent-extractant" for tin from aqueous solution. Distribution coefficients up to 5.6 x 10(3) were obtained and the capacity of the foam was up to 8% tin by weight.     

软质聚氨酯泡沫塑料用无卤阻燃剂的研究

本文以羟基苯氧膦丙烯酸(CEPP)和三聚氰胺(MA)为原料合成了一种含磷、氮无卤阻燃剂(CMA),采用FT-IR表征了阻燃剂的化学结构,并将该阻燃剂用于软质聚氨酯泡沫(FPUF)的阻燃。用扫描电镜(SEM)研究了阻燃剂的加入对FPUF的形态的影响,通过LO I和垂直燃烧(Cal.117A)测试研究了该阻燃剂对FPUF的阻燃效果。结果表明,CMA可以有效提高FPUF的阻燃性:当CMA的添加量为10%时,FPUF即可通过Cal.117A测试,其LO I值也从17.3提高到23.0;随阻燃剂添加量的增加,FPUF的阻燃性能也逐渐提高。TG测试结果表明CMA的加入对FPUF的热稳定性没有多大影响。     

Effects of biopitch on the properties of flexible polyurethane foams

Biopitches are industrial residues obtained by the distillation of the tar recovered during Eucalyptus charcoal production and can be used as a renewable polyol source. Flexible polyurethane foams were prepared with different proportions of biopitch and HTPB (hydroxyl-terminated polybutadiene) and using polymeric MDI (4,4′ diphenyl methane diisocyanate), N,N dimethylcyclohexylamine as a catalyst and water as a blowing agent. Elemental analysis, thermal analysis (TG/DSC), Fourier Transform Infrared Spectroscopy (FTIR), scanning electronic microscopy (SEM), and density results were used aiming to discuss the contribution of biopitch to foams properties. The higher the biopitch content, the higher the thermal stability and the lower the density of the flexible foams (air atmosphere), behaviors similar to those of lignin-based polyurethanes. Biopitch enhanced the oxygen content of the polyurethane foams synthesized, and their reaction with HTPB resulted in stable foams.