Ionomeric interpretation of thickening of polyesters by alkaline earth metal oxides

Four resins of poly(propylene glycol adipate) were mixed with different amounts of MgO and their viscosities were measured after a month. The viscosities increased by several thousand but the increase was less for resins containing more water. The existing explanations of the thickening behavior, namely the polymerization and the coordinate complex formation theories, were found to be inadequate in accounting for the observations. Small-angle x-ray scattering (SAXS) and transmission electron microscopy (TEM) of the thickened resins revealed formation of aggregates of magnesium ions, much like those observed in other ionomers. It is postulated that domain formation is the cause of observed thickening. A correlation between the viscosity of thickened resins and the amount of metal oxide reacted, the water content, and other properties of resin was obtained.     

Analysis of products of the thickening reaction between polyesters and magnesium oxide

The products of the reaction between MgO and polypropylene-glycol adipates of different acid values and water contents were analyzed for the water generated and the magnesium reacted into the resin by means of Karl Fischer titration and atomic absorption spectroscopy, respectively. The results conclusively show that both basic and neutral salts are present in the products. The ratio of the amounts of basic and neutral salts present in the mixture, r_B/N, could also be calculated from the results. It was found that as R, the moles of MgO added per mole of acid groups, is increased both the amount of oxide reacted and r_B/N increase while these are relatively unaffected by the water content of the resin. The minimum value of R at which basic salt exists in the reaction products was found to increase with decreasing acid value. It is proposed that diffusional effects account for these observations as well as those reported in literature.     

Au nanoparticles and polyaniline coated resin beads for simultaneous catalytic oxidation of glucose and colorimetric detection of the product

In this letter, we report the synthesis of Au nanoparticles (NPs) and polyaniline (PANI) on the same cation-exchange resin beads and demonstrate their use in catalyzing the oxidation of glucose to gluconic acid by Au NPs and simultaneously in detecting the formation of the acid by the color change of PANI. The synthesis was carried out by exchanging the cations of the resins with HAuCl4 and anilinuium chloride and then reducing the metal ions by NaBH4 to produce Au NPs followed by polymerization of aniline using H2O2. The green emeraldine salt form of PANI thus obtained was treated with NaOH to be converted to blue emeraldine base before use. The deposition of Au NPs was confirmed by a change in color of the bead, visible spectroscopy, X-ray diffraction, and scanning electron microscopic measurements. On the other hand, the presence of PANI was confirmed by Fourier transform infrared (FTIR) and ultraviolet-visible (UV-vis) spectroscopy. The formation of gluconic acid from glucose was confirmed by FTIR spectroscopy. We could detect the presence of glucose of a minimum 1.0 mM concentration in water, using the present method. Our experimental observations demonstrate the possibility of the incorporation of multifunctional components on the surfaces of resins for carrying out a chemical reaction as well as detection of the product.     

Reductive sorption of molecular oxygen from water on silver-KU-23 sulfo-cation exchanger nanocomposites in different ionic forms

New silver-containing nanocomposites different in their dispersity of metal were synthesized on the basis of strongly and weakly basic anion-exchange resins. The chemical activity of the nanocomposites with respect to oxygen dissolved in water was investigated. It was shown that silver nanoparticles in samples based on strongly basic anion exchangers and weakly basic anion exchangers in the NO₃⁻ salt form are not oxidized by oxygen; for weakly basic matrices in the free amine form, this process occurs to only a small extent. The resistance to oxygen is explained by inhibition of processes of formation of silver oxides. Nanocomposites based on strongly basic anion-exchange resins are recommended for testing as to catalytic activity.     

Chemical activity of silver nanoparticles in anion-exchange matrices with respect to molecular oxygen dissolved in water

New silver-containing nanocomposites different in their dispersity of metal were synthesized on the basis of strongly and weakly basic anion-exchange resins. The chemical activity of the nanocomposites with respect to oxygen dissolved in water was investigated. It was shown that silver nanoparticles in samples based on strongly basic anion exchangers and weakly basic anion exchangers in the NO ₃ ^? salt form are not oxidized by oxygen; for weakly basic matrices in the free amine form, this process occurs to only a small extent. The resistance to oxygen is explained by inhibition of processes of formation of silver oxides. Nanocomposites based on strongly basic anion-exchange resins are recommended for testing as to catalytic activity.     

Activity of metal chromate and phosphate supported on ion‐exchange resins toward hydrogen peroxide decomposition

The mixed resins, Dowex MR‐3 and MR‐12, in the H⁺/Cl⁻ form, and the cation resin, Dowex‐50W, in the H⁺ form, were used as a support for some metal chromate and phosphate salts. Similarly, anionic resin, Amberlite IRA‐400, in the Cl⁻ form, was used as a support for some metal chromate salts. The activity of these metal salt‐supported on four different resins toward hydrogen peroxide decomposition was investigated. The decomposition of H₂O₂, with these catalysts, was found to follow first‐order kinetics with respect to [H₂O₂]. Factors that affected the rate of reaction, such as mesh size of the support, amount of supported salt, and the electrostatic interactions, were investigated. With Ag(I)‐chromate supported on mixed resin MR‐3 in the Ag⁺/NO₃⁻ form, the rate of reaction was greater than that with the mixed resin MR‐12 in the same form. Moreover, the rate with Ag(I) chromate supported on the anion resin IRA‐400 in the R‐NO₃⁻ form was greater than mixed resins. Also, the rate with Fe(III) chromate supported on Amberlite IRA‐400 in the R‐CrO₄²⁻ form was greater than other counter‐anionic forms as well as Dowex‐50W resin in the metal ion form. However, Fe(III)‐chromate supported on cation resin R‐Fe³⁺ showed greater activity than other cationic forms. On the other hand, the rate with MR‐3 resin in the Na⁺/PO₄³⁻ form was greater than that in the presence of supported Fe(III) phosphate. However, the rate of reaction increased when Fe(III) was replaced by Ba(II). Iron(III) phosphate supported on Dowex‐50W resin in the Na⁺ form showed greater activity compared to MR‐3 resin in the Na⁺/PO₄³⁻ form. In the case of Fe(III) phosphate supported on mixed resin MR‐12, the rate was much greater than that with unsupported resin. However, when Ba(II) phosphate was incorporated instead of Fe(III) phosphate, the rate of reaction increased considerably. The activity of Fe(III) chromate is greater than that of Fe(III) phosphate supported on the same cation resin. Activation parameters were evaluated and a probable reaction mechanism was proposed. © 2000 John Wiley & Sons, Inc. Int J Chem Kinet 32: 667–675, 2000     

Characterisation of solute mobility in hypercross-linked resins in solvents of different polarity: two promising supports for catalysis

Two hypercross-linked resins stemming from a gel-type poly-chloromethylated styrene-divinylbenzene resin (GT) in beaded form are investigated with a combination of spectroscopic techniques (EPR and time-domain (TD)-NMR spectroscopy) to evaluate their use as supports for the development of operationally flexible heterogeneous metal catalysts, suitable to be employed in liquid and gas phase. The first resin (HGT) is the direct product of the hypercross-linking reaction, whereas the second one (HGS) is the sulphonated analogue of HGT obtained by exchanging approximately 3?wt?% of the chloromethyl groups with sulphonic groups. HGT and HGS absorb both polar and apolar solvents in the permanent nanoporosity created by the hypercross-linking, and NMR data highlight that the pore size is not affected by the different properties of the investigated liquid media. The EPR analysis of the dry resins reveals that during the hypercross-linking process paramagnetic species are formed in the HGT beads, which persist in the sulphonated resin. The mobility of solutes inside the polymers framework was investigated with EPR spectroscopy upon soaking the resins with solutions of two spin probes (2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) and 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPOL)) in THF, toluene, n-heptane and water. The EPR spectra show that, depending on the solvent, the two resins can act as sorbents, able to trap the solutes in the polymer framework, or as simple supports that allow free diffusion of the solutes. Our results suggest that HGT and HGS are promising supporting materials for metal catalysts, provided one chooses carefully the solvent to be employed for the catalysed reaction as this choice strongly affects the mobility of the substrates and, thus their effective reactivity.     

Characterisation of Solute Mobility in Hypercross‐Linked Resins in Solvents of Different Polarity: Two Promising Supports for Catalysis

Two hypercross‐linked resins stemming from a gel‐type poly‐chloromethylated styrene‐divinylbenzene resin (GT) in beaded form are investigated with a combination of spectroscopic techniques (EPR and time‐domain (TD)‐NMR spectroscopy) to evaluate their use as supports for the development of operationally flexible heterogeneous metal catalysts, suitable to be employed in liquid and gas phase. The first resin (HGT) is the direct product of the hypercross‐linking reaction, whereas the second one (HGS) is the sulphonated analogue of HGT obtained by exchanging approximately 3 wt % of the chloromethyl groups with sulphonic groups. HGT and HGS absorb both polar and apolar solvents in the permanent nanoporosity created by the hypercross‐linking, and NMR data highlight that the pore size is not affected by the different properties of the investigated liquid media. The EPR analysis of the dry resins reveals that during the hypercross‐linking process paramagnetic species are formed in the HGT beads, which persist in the sulphonated resin. The mobility of solutes inside the polymers framework was investigated with EPR spectroscopy upon soaking the resins with solutions of two spin probes (2,2,6,6‐tetramethylpiperidine‐1‐oxyl (TEMPO) and 4‐hydroxy‐2,2,6,6‐tetramethylpiperidine‐1‐oxyl (TEMPOL)) in THF, toluene, n‐heptane and water. The EPR spectra show that, depending on the solvent, the two resins can act as sorbents, able to trap the solutes in the polymer framework, or as simple supports that allow free diffusion of the solutes. Our results suggest that HGT and HGS are promising supporting materials for metal catalysts, provided one chooses carefully the solvent to be employed for the catalysed reaction as this choice strongly affects the mobility of the substrates and, thus their effective reactivity.     

Kinetics of Neutralization of Weak Electrolyte Ion-Exchange Resins

The adsorption of acids and alkalis by weak electrolyte resins is described by diffusion of the ions through the resin bead, with an accompanying neutralization reaction. A model proposed by Helfferich has been extended to account for the situation where the solution concentration of the reagent is changing during the rate experiment. Two mechanisms are necessary, depending on the concentration of the reagent. The rate expression for systems where the reagent concentration is greater than 0.01 M is given. It predicts that the adsorption rate is dependent on the solution hydrogen ion concentration in the case of weakly basic resins, and that it varies inversely with the square of the particle radius. The rate should also be unchanged by the resin of added salt.

Experimental evidence in the form of rate data for the uptake of hydrochloric acid by a commercial weakly basic resin support the derived equation, which can be modified further to account for the diffusional resistance of the liquid film around the resin particle.     

“非保护型”金属胶体纳米簇形成机理研究

碱-乙二醇法制备的"非保护型"金属及合金纳米簇由表面吸附的溶剂分子和简单离子实现稳定化,它们被广泛用于制备高性能复相催化剂和研究复相催化剂中的尺寸、组成、载体表面基团以及修饰剂对催化性能的影响。关于此类非保护金属纳米簇的形成过程及机理的认识尚有待进一步深化。本文采用原位快速扫描X射线吸收精细结构谱(QXAFS)、原位紫外-可见(UV-Vis)吸收光谱、透射电子显微镜和动态光散射技术研究了碱-乙二醇法合成中非保护型金属胶体纳米簇的形成过程与机理。结果表明,在碱-乙二醇法合成非保护型Pt金属纳米簇的过程中,室温下即有部分Pt(IV)被还原至Pt(II)。随着反应温度的升高,OH-逐渐取代与Pt离子配位的Cl-,在Pt―Pt键形成之前,反应体系的UV-Vis吸收光谱中可观察到明显的纳米粒子的散射信号,原位QXAFS分析表明Pt纳米簇是由Pt氧化物纳米粒子还原所形成的;在Ru金属纳米簇的形成过程中,OH-首先取代了Ru Cl_3中的Cl~-,形成羟基配合物Ru(OH) _6~(3-),后者进一步缩合形成氧化钌纳米粒子,最终Ru金属纳米簇由乙二醇还原氧化钌纳米粒子形成。由于先形成了氧化物纳米粒子,后续的还原反应被限制在氧化物纳米粒子内,使最终得到的非保护型金属纳米簇具有尺寸小、分布窄的特点。本工作所获得的知识对发展高性能能源转化催化剂、精细化学合成催化剂、传感器等功能体系具有重要意义。     

Study on liquid oxygen compatibility of bromine‐containing epoxy resins for the application in liquid oxygen tank

The liquid oxygen compatible epoxy resin was obtained by the polycondensation between tetrabromobisphenol A and neat epoxy resins. The results of liquid oxygen impact test indicated that the synthetic epoxy resins were compatible with liquid oxygen. The relationship between impact reaction sensitivity (IRS) and flame retardancy were studied by liquid oxygen impact test and limiting oxygen index test. The results showed that the flame‐retardant modification of epoxy resin was valuable to reduce the IRS. The thermal gravimetric analysis results indicated that the Br · radical was quickly released in relatively low temperature (approximately 370°C) for compatible epoxy resin. The Br · radical was a key factor to promote the epoxy resin compatible with the liquid oxygen. The X‐ray photoelectron spectroscopy was used to survey the distribution of functional groups on the surface of samples before and after impact. The results showed that the oxidation reaction and carbonization process may occur on the surface of samples after impact. The liquid oxygen compatibility mechanism is proposed in this paper. The bromine‐containing epoxy resin has the potential to be the material used in liquid oxygen tank. Copyright © 2015 John Wiley & Sons, Ltd.     

对-氨基苯甲酸改性环氧树脂的性能表征及乳化性质

以对氨基苯甲酸改性环氧树脂,使其成为具有亲水性的树脂.实验结果表明,改性后树脂在有机溶剂中的溶解性变差,在碱性溶剂中溶解性增强.对改性树脂进行了红外表征,并根据环氧基特征峰的吸收对环氧基转化率进行了定量分析.测定了改性产物的DSC曲线,发现随着反应物中对氨基苯甲酸比例的升高,改性产物的玻璃化转变温度升高.此外还研究了改性环氧树脂水基微乳液制备过程的电导率变化规律,并探讨了羧酸基中和程度及溶剂极性对乳液粒径以及粒子形态的影响.     

Comparisons of sorption of aquatic humic matter by DAX-8 and XAD-8 resins from solid-state (13)C NMR spectroscopy's point of view

Aquatic humic solutes were separated in parallel by the non-ionic macroporous DAX-8 and XAD-8 resins from four different fresh water sources. On average, the sorptive power of the DAX-8 resin does not differ systematically from that of the XAD-8 resin. The DAX-8 resin seems to have more precise column characteristics compared with the XAD-8 resin. There was no significant difference between the major elemental compositions of the parallel humic-solute bulks obtained by these two resins. According to the (13)C NMR spectroscopy the content and quality of aliphatic carbons, especially those representing terminal methyl groups or methylene carbons, were the most systematic and powerful discriminating factors between the humic extracts obtained by these two resins. Generally speaking the DAX-8 and XAD-8 resins seem to isolate humic-solute bulks almost equally, although the content of aliphatics is slightly greater for the former, producing mixtures with similar structural compositions for general purposes. The structural composition and quantity of the humic-solute mixture isolable with a weakly basic DEAE-cellulose anion exchange resin differs partially from any humic fraction obtained by non-ionic sorbing solids. The environmental impact was also visible on the quality of the structural fine-chemistry of the different humic isolates obtained both by the DAX-8 and XAD-8 resins.     

Organic/inorganic hybrid epoxy nanocomposites based on octa(aminophenyl)silsesquioxane

Octa(aminophenyl)silsesquioxane (OAPS) was used as the curing agent of diglycidyl ether of bisphenol-A (DGEBA) epoxy resin. A study on comparison of DGEBA/OAPS with DGEBA/4,4′-diaminodiphenyl sulfone (DDS) epoxy resins was achieved. Differential scanning calorimetry was used to investigate the curing reaction and its kinetics, and the glass transition of DGEBA/OAPS. Thermogravimetric analysis was used to investigate thermal decomposition of the two kinds of epoxy resins. The reactions between amino groups and epoxy groups were investigated using Fourier transform infrared spectroscopy. Scanning electron microscopy was used to observe morphology of the two epoxy resins. The results indicated that OAPS had very good compatibility with DGEBA in molecular level, and could form a transparent DGEBA/OAPS resin. The curing reaction of the DGEBA/OAPS prepolymer could occur under low temperatures compared with DGEBA/DDS. The DGEBA/OAPS resin didn’t exhibit glass transition, but the DGEBA/DDS did, which meant that the large cage structure of OAPS limited the motion of chains between the cross-linking points. Measurements of the contact angle indicated that the DGEBA/OAPS showed larger angles with water than the DGEBA/DDS resin. Thermogravimetric analysis indicated that the incorporation of OAPS into epoxy system resulted in low mass loss rate and high char yield, but its initial decomposition temperature seemed to be lowered.     

Qualitative spectroscopic characterization of the matrix–silane coupling agent interface across metal fibre reinforced ion exchange resin composite membranes

The characterization of novel metal reinforced electro-dialysis ion exchange membranes, for water desalination, by attenuated total reflectance Fourier transform infrared spectroscopy mapping is presented in this paper. The surface of the porous stainless steel fibre meshes was treated in order to enhance the amount of surface oxide groups and increase the material hydrophilicity. Then, the metal membranes were functionalized through a sol–gel reaction with silane coupling agents to enhance the affinity with the ion exchange resins and avoid premature metal oxidation due to redox reactions at the metal–polymer interface. Polished cross sections of the composite membranes embedded into an epoxy resin revealed interfaces between metallic frameworks and the silane layer at the interface with the ion exchange material. The morphology of the metal–polymer interface was investigated with scanning electron microscopy and Fourier transform infrared micro-spectroscopy. Fourier transform infrared mapping of the interfaces was performed using the attenuated total reflectance mode on the polished cross-sections at the Australian Synchrotron. The nature of the interface between the metal framework and the ion exchange resin was shown to be homogeneous and the coating thickness was found to be around 1 μm determined by Fourier transform infrared micro-spectroscopy mapping. The impact of the coating on the properties of the membranes and their potential for water desalination by electro-dialysis are also discussed.     

Preparation and degradation of salts of poly(methacrylic acid)—Part II: Magnesium,calcium, strontium and barium salts

The thermal degradation behaviour of the alkaline earth metal polymethacrylates has been compared with that of the corresponding acetates and that of the alkali metal polymethacrylates, using thermal volatilisation analysis, thermogravimetry and analysis of the several product fractions and partially degraded polymer. The salt polymers resemble the acetates only in the order of their stabilities which increase with the size of the metal ion. Chain scission and depolymerisation, which was found to be an important process in the alkali metal polymethacrylate series, cannot occur to the same extent in the alkaline earth metal series because, except in the case of the magnesium salt, the monomers are involatile and cannot distil out of the reaction zone. The alternative process, involving formation of ketones and metal carbonate or oxide, therefore predominates. There is some evidence that chain scission occurs in the case of magnesium polymethacrylate. The mechanism of degradation is discussed.     

Synthesis and properties of a chelating resin containing triazolethiol groups

A macroreticular poly(acrylic acid)-based resin with triazolethiol as the functional group has been synthesized. The stability of the resin in acidic media and the behaviour in sorption and desorption of various metal ions have been investigated and compared with those of the acylthiosemicarbazide resin which is an intermediate in synthesis of the triazolethiol resin. Both resins show high affinity for copper(II) silver, cadmium and mercury(II), and high selectivity for silver and mercury(II) at low pH (1–2), and even at pH 7 if EDTA is present. The triazolethiol resin sorbs metal ions faster than the acylthiosemicarbazide resin does and sorbs mercury(II) from high concentrations of acids and neutral salt solutions. This resin has been applied to the concentration of silver and mercury(II) from sea-water samples by column operation.     

Synthesis and metal binding behavior of hydroxamic acid resins from poly(ethyl acrylate) crosslinked with divinylbenzene and hydrophilic crosslinking agent

Porous poly(hydroxamic acid) chelating resin was prepared by the reaction with poly(ethyl acrylate) crosslinked with divinylbenzene and hydrophilic crosslinking agent, and hydroxylamine. The hydrophilic crosslinking agents and diluent used in this article were ethylene glycol dimethacrylate or butanediol dimethacrylate, and 2,2,4-trimethyl pentane, respectively. The characterization of this type chelating resin was carried out by IR spectroscopy, density measurement, and scanning electron microscopy. Various metal binding properties such as extraction, kinetics, and selectivity were investigated with atomic absorption spectrometer and inductively coupled plasma spectrometer. Poly(hydroxamic acid) resins crosslinked with mixed crosslinking agents showed better metal extraction properties and faster adsorption rate than those crosslinked with divinylbenzene alone. And alkali treatment enhances the binding rate for metal ions because of the formation of other chelating ligands or micropores. © 1995 John Wiley & Sons, Inc.     

Characterization of transition metal nitride formation in rapid thermal processing (RTP)

The potential of RTP for the preparation of transition metal nitrides by reaction of metal thin films in molecular nitrogen was investigated. The films and the nitridation process were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), energy dispersive x-ray analysis (EDX) in a scanning electron microscope (SEM) and secondary neutral mass spectrometry (SNMS). The chemical states of vanadium at the utmost surface, detected by XPS, are related to V₂O₅ before RTP and to vanadium nitride, oxide and oxynitride after RTP. The deposition of a 3 nm Si top layer prevents V from oxidation and its selective removal before RTP enhances the proportion of nitride determined by XPS after RTP. From comparative experiments in a conventional tube furnace the advantages of RTP became obvious. With short process times of the RTP technique the integral amount of residual oxygen is kept low and oxide formation is largely avoided. The nitrogen content and the different polycrystalline phases formed by varying process time and temperature provide information about reactivity and the nitridation process. The nitrogen to vanadium ratio was determined by EDX and SNMS, revealing that the N content reaches saturation after only 5 seconds at 1100?°C.     

Study of the reaction of polyester resins with magnesium oxide

The reaction of polyester resin and magnesium oxide, which is the basis of the thickening process of sheet-molding compound technology, has been characterized in a systematic study. The effect of reactant equivalency ratios, temperature, and added water on viscosity development have been determined. Excess amounts of magnesium oxide are necessary for thickening. Water increases the initial rate of thickening but reduces the overall level attained. A new thickening mechanism is proposed on the basis of a model study with polyester resin and sodium hydroxide.