Electrochemical behavior of europium (III) in N-butyl-N-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide

N-butyl-N-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide (BMPyNTf₂) was synthesized and characterized by CHNS elemental analysis, ¹H and ¹³C NMR and IR spectroscopy. Europium tris[bis(trifluoromethylsulfonyl)imide] (Eu(NTf₂)₃) was prepared and studied for the electrochemical behavior of Eu(III) in BMPyNTf₂ at glassy carbon and stainless steel working electrodes at 298-373 K by cyclic voltammetry, chronopotentiometry and chronoamperometry. Cyclic voltammogram of Eu(III) in BMPyNTf₂ consisted of a quasi-reversible cathodic wave at −0.45 V (vs. Fc/Fc⁺, 373 K), which could be attributed to the reduction of Eu(III) to Eu(II) and an irreversible wave at −2.79 V (vs. Fc/Fc⁺) due to reduction of Eu(II) to Eu(0). The diffusion coefficient of Eu(III) in BMPyNTf₂ was determined to be in the range of ∼10⁻⁷ cm² s⁻¹ by various electrochemical methods and the charge transfer rate constant was determined to be ∼10⁻⁵ cm s⁻¹ by cyclic voltammetry.     

Cure Kinetics and Sorption Characteristics of Neoprene-Based Rubber Ferrite Composites

Rubber ferrite composites were prepared by incorporating nickel ferrite in a neoprene rubber matrix. Kinetics of the cure reaction were determined from the rheometric torque values and found to follow first-order kinetics. Analysis of the swelling behavior of the rubber ferrite composites in toluene elucidates the mechanism of solvent penetration and sorption characteristics, and reveals the extent of the physical interaction of the ferrite particles with the neoprene rubber matrix. Mechanical properties of rubber ferrite composites were determined, which support the reinforcing nature of nickel ferrite to the neoprene rubber matrix. These results show that magnetic composites with the required processing safety can be prepared economically by incorporating higher amounts of nickel ferrite in the neoprene rubber matrix.     

Curing Characteristics and Aging Properties of Natural Rubber/Epoxidized Natural Rubber and Cellulose II

In this work, natural rubber (NR) and regenerated cellulose (cel II) latexes were co-coagulated and to the mixture epoxidized natural rubber (ENR) was added on a two-roll mill. The cellulose content was fixed at 20 phr while ENR content varied from 0 to 75 phr. The influence of ENR was studied through the cure characteristics, aging and dynamic-mechanical properties. The aging provides nanocomposites with better solvent resistance and increased tensile strength at ENR content of 25 phr. The results suggest that a new type of light-colored nanocomposites were obtained, which presented high mechanical performance and resistance to solvents.     

茶多酚改性天然胶乳复合材料的制备及性能研究

以多羟基结构的茶多酚作界面改性剂,制备了埃洛石纳米管/天然胶乳复合材料及二氧化硅/天然胶乳复合材料,研究了茶多酚对复合材料界面作用及力学性能的影响。结果表明,茶多酚分别能与埃洛石纳米管和二氧化硅形成氢键,改善了填料与橡胶基体间的界面作用。茶多酚改性天然胶乳复合材料的力学性能显著提高,其原因归因于复合材料界面状态的改善。     

Curing Characteristics and Mechanical Properties of Oil Palm Wood Flour Reinforced Epoxidized Natural Rubber Composites

Abstract

The paper reports on the curing characteristics and mechanical properties of oil palm wood flour (OPWF) reinforced epoxidized natural rubber (ENR) composites. Three sizes of OPWF at different filler loadings were compounded with a two roll mill. The cure (t ₉₀) and scorch times of all filler size decrease with increasing OPWF loading. Increasing OPWF loading in ENR compound resulted in reduction of tensile strength and elongation at break but increased tensile modulus, tear strength and hardness. The composites filled with smaller OPWF size showed higher tensile strength, tensile modulus and tear strength. Scanning electron microscope (SEM) micrographs showed that at lower filler loading the fracture of composites occurred mainly due to the breakage of fibre with minimum pull-out of fibres from the matrix. However as the filler loading is increased, the fibre pull-out became very prominent due to the lack of adhesion between fibre and rubber matrix.     

Efficient and Eco‐Friendly Process for the Synthesis of Bis(1H‐indol‐3‐yl)methanes using Ionic Liquids

Indoles react smoothly with carbonyl compounds in 1‐butyl‐3‐methylimidazolium tetrafluoroborate ([bmim]BF₄) or 1‐butyl‐3‐methylimidazolium hexafluorophosphate ([bmim]PF₆) ionic liquids under mild reaction conditions to afford the corresponding bis‐indolylmethanes in excellent yields. These ionic liquids can be recovered and recycled in subsequent reactions without any apparent loss of activity.     

Influence of Alkyl Chain Length on Thermal Properties,Structure, and Self-Diffusion Coefficients of Alkyltriethylammonium-Based Ionic Liquids

The application of ionic liquids (ILs) has grown enormously, from their use as simple solvents, catalysts, media in separation science, or electrolytes to that as task-specific, tunable molecular machines with appropriate properties. A thorough understanding of these properties and structure–property relationships is needed to fully exploit their potential, open new directions in IL-based research and, finally, properly implement the appropriate applications. In this work, we investigated the structure–properties relationships of a series of alkyltriethylammonium bis(trifluoromethanesulfonyl)imide [TEA-R][TFSI] ionic liquids in relation to their thermal behavior, structure organization, and self-diffusion coefficients in the bulk state using DSC, FT-IR, SAXS, and NMR diffusometry techniques. The phase transition temperatures were determined, indicating alkyl chain dependency. Fourier-transformed infrared spectroscopy studies revealed the structuration of the ionic liquids along with alkyl chain elongation. SAXS experiments clearly demonstrated the existence of polar/non-polar domains. The alkyl chain length influenced the expansion of the non-polar domains, leading to the expansion between cation heads in polar regions of the structured IL. ¹H NMR self-diffusion coefficients indicated that alkyl chain elongation generally caused the lowering of the self-diffusion coefficients. Moreover, we show that the diffusion of anions and cations of ILs is similar, even though they vary in their size.     

Ionogels Based on Poly(methyl methacrylate) and Metal-Containing Ionic Liquids: Correlation between Structure and Mechanical and Electrical Properties

Ionogels (IGs) based on poly(methyl methacrylate) (PMMA) and the metal-containing ionic liquids (ILs) bis-1-butyl-3-methlimidazolium tetrachloridocuprate(II), tetrachloride cobaltate(II), and tetrachlorido manganate(II) have been synthesized and their mechanical and electrical properties have been correlated with their microstructure. Unlike many previous examples, the current IGs show a decreasing stability in stress-strain experiments on increasing IL fractions. The conductivities of the current IGs are lower than those observed in similar examples in the literature. Both effects are caused by a two-phase structure with micrometer-sized IL-rich domains homogeneously dispersed an IL-deficient continuous PMMA phase. This study demonstrates that the IL-polymer miscibility and the morphology of the IGs are key parameters to control the (macroscopic) properties of IGs.     

Solubility of CO2 in Methanol, 1-Octyl-3-methylimidazolium Bis(trifluoromethylsulfonyl)imide, and Their Mixtures

Solubility data of carbon dioxide (CO₂) (1) in methanol (2), 1-octyl-3-methylimidazolium bis(trifluoro- methylsulfonyl)imide ([omim]⁺[Tf₂N]^-) (3), and their mixtures (w₃ 0.2, 0.5, and 0.8) at temperatures 313.2 and 333.2 K and pressures up to 7.0 MPa were measured by a high-pressure view-cell technique. The solubility of CO₂ in methanol (w₃=0), [omim]⁺[Tf₂N]^- (w₃=1.0) and their mixtures follows the order of (w₃=0)<(w₃=0.2)< (w₃=0.5)<(w₃=0.8)<(w₃=1.0) at the same temperature and pressure, while the magnitude of Henry's constants follows the reverse order at a given temperature, which is consistent with the COSMO-RS (conductor-like screening for real solvents) calculation. The solubility data of CO₂ in methanol and [omim]⁺[Tf₂N]^- are correlated with the Peng-Robinson equation of state, and the solubility of CO₂ in the mixtures of methanol and [omim]⁺[Tf₂N]^- can be well predicted based on the mole fraction average of methanol and [omim]⁺[Tf₂N]^- over the solubility of CO₂ in pure methanol and [omim]⁺[Tf₂N]^-. The mixtures of methanol and [omim]⁺[Tf2N]^- may be used as physical solvents for capturing CO₂ with high partial pressures since they combine the advantages of organic solvents and ionic liquids.     

Extractive Desulfurization of Fuel Oils with Dicyano(nitroso)methanide-based Ionic Liquids

The inability of traditional hydrodesulfurization (HDS) to effectively remove aromatic sulfur compounds such as thiophene (TS) and dibenzothiophene (DBT) has called for alternative methods to be studied, among which extractive desulfurization using ionic liquids (ILs) has attracted increasing interest. In this work, we prepared a new IL, 1-butyl-3-methylimidazolium dicyano(nitroso)methanide ([C₄mim][dcnm]), and investigated its extractive desulfurization for both model oils and real FCC gasoline, where model diesel fuel was composed of n-hexane and droplets of DBT and model gasoline was composed of n-hexane, toluene and droplets of TS. Other three [dcnm]-based ILs, 1-ethyl-3-methylimidazolium dicyano(nitroso)methanide ([C₂min][dcnm]), N-ethyl-N-methylpyrrolidinium dicyano(nitroso)methanide ([C₂mpyr][dcnm]), and N-butyl-N-methylpyrrolidinium dicyano(nitroso)methanide ([C₄mpyr][dcnm]), were also comparatively investigated. These [dcnm]-based ILs have low viscosity which favors the mass transfer and reduces the extractive equilibrium time, also are fluorine-free which avoids the corrosion by hydrogen fluoride from anion decomposition that occurs generally in fluorine-containing ILs. The desulfurization ability follows the order [C₄min][dcnm] > [C₄mpyr][dcnm] > [C₂min][dcnm] > [C₂mpyr][dcnm]. Typically, [C₄min][dcnm] is capable of removing 66% DBT and 53% TS from their respective model oils after one cycle (initial 500 ppm S, 25°C, 15 min, mass ratio of IL:oil 1:1), and < 10 ppm S-content can be obtained after 4 cycles. It was observed interestingly that the S-content in real FCC gasoline can be reduced from initial 250 ppm to < 30 ppm after 6 cycles using [C₄min][dcnm] as extractive reagent, which is better than some previous results for real feedstocks. Mutual solubility, extractive temperature, IL:oil mass ratio, multiple extraction, initial S-content, and regeneration were also studied. These dcnm-based ILs are competitive extractive reagents compared with some other ILs to remove those aromatic S-compounds from fuel oils.     

The Potential Application of Starch and Walnut Shells as Biofillers for Natural Rubber (NR) Composites

The goal of this study was application of corn starch and ground walnut shells in various amounts by weight as biofillers of natural rubber (NR) biocomposites. Additionally, ionic liquid 1-butyl-3-methylimidazolium chloride (BmiCl) and (3-aminopropyl)-triethoxysilane (APTES) were used to increase the activity of biofillers and to improve the curing characteristics of NR composites. The effect of biofillers used and their modification with aminosilane or ionic liquid on the curing characteristics of NR composites and their functional properties, including crosslink density, mechanical properties in static and dynamic conditions, hardness, thermal stability and resistance to thermo-oxidative aging were investigated. Starch and ground walnut shells were classified as inactive fillers, which can be used alternatively to commercial inactive fillers, e.g., chalk. BmiCl and APTES were successfully used to support the vulcanization and to improve the dispersion of biofillers in NR elastomer matrix. Vulcanizates with starch, especially those containing APTES and BmiCl, exhibited improved tensile properties due to the higher crosslink density and homogenous dispersion of starch, which resulted from BmiCl addition. NR filled with ground walnut shells demonstrated improved resistance to thermo-oxidative aging. It resulted from lignin present in walnut shells, the components of which belong to polyphenols, that have an antioxidant activity.     

Cu(I)-Based Ionic Liquids as Potential Absorbents to Separate Propylene and Propane

The absorption of propylene and propane in Cu(I)-based ionic liquids, i.e., 1-butyl-3-methylimidazolium chloride/CuCl ([Bmim][Cl]/CuCl), N-Methyl pyrrolidone chloride/CuCl ([HNMP][Cl]/CuCl), and tricaprylmethylammonium thiocyanate/CuSCN ([A336][SCN]/CuSCN), are investigated in this work. It is observed that such Cu(I)-based ionic liquids, especially Bmim-based ionic liquids, present good absorption capability for propylene and good selectivity over propane, e.g., 1.0 kilogram [Bmim][Cl]/CuCl is able to absorb 0.08 mol propylene while only 0.006 mol propane at 25°C and 1.3 bar with the selectivity of 13. The effects of pressure, Cu⁺ concentration, and temperature on the absorption are investigated; in addition, the absorption kinetics of propylene by [Bmim][Cl]/CuCl is obtained. The much higher absorption capability for propylene than propane is ascribed to the π-complexation between propylene and Cu⁺. This work shows that the absorption by Cu(I)-based ionic liquids is an potential alternative method for traditional cryogenic distillation with high energy cost to separate propylene and propane.     

The Effect of Accelerator/Sulphur Ratio on the Cure Time and Torque Maximum of Epoxidized Natural Rubber

Abstract

The cure time of accelerated sulphur vulcanization of Epoxidized Natural Rubber (ENR 25) was studied while one grade of unmodified natural rubber– Standard Malaysian Rubber Light (SMR L) was used as a control. Five accelerators, viz. 2-mercaptoben-zothiazole (MBT), tetramethylthiuram disulphide (TMTD), zinc dimethyldithiocarbamate (ZDMC), N-tert-butyl-2-benzothiazylsulphenamide (TBBS) and diphenylguanidine (DPG) were used in the study and the vulcanization systems used were conventional vulcanization (CV), semi-efficient vulcanization (semi-EV) and efficient vulcanization (EV). Monsanto Moving-Die Rheometer (MDR 2000) was used to determined the cure time in the temperature range of 100-180°C. The results indicate that cure time decreases exponentially with increasing temperature for the two rubbers studied. At a fixed curing temperature, ENR 25 shows shorter cure time compared to that of SMR L. This has been attributed to the activation of the double bond by the adjacent epoxide group in ENR 25. Studies of the effect of varying amounts of M Bata a fixed sulphur concentration show that cure time decreases as the accelerator concentration increases. ENR 25 shows higher torque maximum than SMR L. This observation can be related to the oxirane group which is bulky and thus accounts for increased glass; transition temperature with increase in the level of epoxidation. Of the vulcanization systems, CV shows the highest torque maximum followed by semi-EV and than EV. This trend can be attributed to the amount of active sulphurating agent which increases with increasing accelerator concentration. It was also found that the influence of accelerator/sulphur ratio becomes less significant as vulcanization temperature increases.     

Electrodeposition of palladium in a hydrophobic 1-n-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide room-temperature ionic liquid

The electrochemical reduction of palladium halide complexes such as PdBr₄²⁻ and PdCl₄²⁻ was investigated in a hydrophobic room-temperature ionic liquid (RTIL), 1-n-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide (BMPTFSI). The irreversible electrode reaction between Pd(II) and Pd(0) was observed in BMPTFSI containing PdBr₄²⁻ or PdCl₄²⁻ by cyclic voltammetry. The diffusion coefficient of PdBr₄²⁻ was estimated to be (1-2) × 10⁻⁷ cm² s⁻¹ by choronopotentiometry and chronoamperometry. The deposition of crystalline Pd metal was confirmed by X-ray diffraction and X-ray photoelectron spectroscopy. It was suggested by the chronoamperometric measurements on PdBr₄²⁻ in BMPTFSI that the initial stage of the electrodeposition of Pd on the polycrystalline Pt electrode surface involves three-dimensional progressive nucleation under diffusion control. The reduction potential of PdCl₄²⁻ was more negative than that of PdBr₄²⁻, reflecting the difference in the donor property between chloride and bromide.     

The Effect of Rice Husk Powder on Standard Malaysian Natural Rubber Grade L (SMR L) and Epoxidized Natural Rubber (ENR 50) Composites

The effects of rice husk powder (RHP) loading and two types of natural rubber matrix (SMR L and ENR 50) on curing characteristics and mechanical properties were studied. The scorch time and cure time decreased with increasing RHP loading whereas maximum torque showed an increasing trend. SMR L composites possessed longer scorch time and cure time than ENR 50 composites. Incorporation of RHP into both rubbers improved tensile modulus significantly but decreased tensile strength and elongation at break. SMR L composites exhibited the lower tensile modulus and higher tensile strength and elongation at break than ENR 50 composites.     

Comparison Properties of Natural Rubber (SMR L)/Ethylene Vinyl Acetate (EVA) Copolymer Blends and Epoxidized Natural Rubber (ENR-50)/Ethylene Vinyl Acetate (EVA) Copolymer Blends

Mixing torque, morphology, tensile properties and swelling studies of natural rubber/ethylene vinyl acetate copolymer blends were studied. Two series of unvulcanized blends, natural rubber/ethylene vinyl acetate (SMRL/EVA) copolymer blend and epoxidized natural rubber (50% epoxidation)/ethylene vinyl acetate (ENR-50/EVA) copolymer blend were prepared. Blends were prepared using a laboratory internal mixer, Haake Rheomix polydrive with rotor speed of 50 rpm at 120°C. Results indicated that mixing torque value and stabilization torque value in ENR-50 blends are lower than SMRL blends. The process efficiency of ENR-50/EVA blends is better due to less viscous nature of the blend compared to SMRL/EVA blends as indicated in stabilization torque graph. Tensile properties like tensile strength, M100 (modulus at 100% elongation) and E _b (elongation at break) increase with increasing EVA fraction in the blend. At the similar blend composition, ENR-50 blend shows better tensile properties than SMRL blends. In oil resistance test, swelling percentage increased with immersion time and rubber composition. At a similar immersion time, ENR-50 blends exhibit better oil resistance compared to SMRL blends. Scanning electron microscopy (SEM) of tensile fractured surface indicated that EVA/ENR-50 blends need higher energy to cause catastrophic failure compared to EVA/SMRL blends. In etched cryogenically fractured surface, size and distribution of holes due to extraction of rubber phase by methyl ethyl ketone (MEK) were studied and holes became bigger as rubber composition increased due to coalescence of rubber particle.     

Electrochemical codeposition of copper and manganese from room-temperature N-butyl-N-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide ionic liquid

The voltammetric behavior of N-butyl-N-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide ionic liquid (BMP-TFSI) containing Cu(I), Mn(II), or mixtures of Cu(I) and Mn(II) as well as the electrodeposition of copper-manganese alloy coatings (Cu-Mn alloy coatings) was studied at 323 K. The Cu(I) and Mn(II) species required to prepare these coatings were introduced into the BMP-TFSI by anodic dissolution of the relevant metallic electrodes. Electrodeposits of Cu, Mn, and Cu-Mn with various contents of Mn can be obtained by controlled-potential electrolysis. It was found that the compositions and surface morphology of the electrodeposited Cu-Mn alloy coatings depend on the deposition potentials and the concentration ratio of [Cu(I)]/[Mn(II)] in BMP-TFSI. The Cu-Mn alloy coatings obtained in this study were compact and adherent. They did not show any significant X-ray diffraction signal that could be assigned to the crystalline structures of Cu, Mn, or Cu-Mn alloys. In the aqueous solution containing 0.1 M NaCl, the Cu-Mn alloy coatings demonstrated passive behavior—no continuous oxidation was observed. However, a significant oxidation current was observed at the electrodes deposited with Cu or Mn.     

Study on Tensile,Electrical, and Thermal Properties of Aluminium Particle Filled Natural Rubber (NR) and Ethylene-Propylene-Diene Terpolymer (EPDM) Composites

Comparative studies on the effect of aluminium particles in natural rubber (NR) and ethylene-propylene-diene terpolymer (EPDM) were conducted. The incorporation of aluminium particles in NR or EPDM composites increased the cure time, t ₉₀, and scorch time, t _S2 . At a fixed filler loading, EPDM composites exhibited longer t ₉₀ and t _S2 than NR composites. The results also indicate that the maximum torque, M _H of aluminium filled NR and EPDM composites increase with increasing filler loading. For tensile properties, EPDM composites show lower tensile properties than NR composites. Thermogravimetric analysis (TGA) results show that aluminium filled EPDM composites have better thermal stability than aluminium filled NR composites.

The results for electrical properties indicate that the electrical properties of aluminium filled NR and EPDM composites increase with increase in filler loading.     

Effect of zinc oxide nanoparticles as cure activator on the properties of natural rubber and nitrile rubber

Zinc oxide (ZnO) nanoparticles were synthesized by homogeneous precipitation and calcination method and were then characterized by transmission electron microscopy and X‐ray diffraction analysis. Synthesized ZnO was found to have no impurity and had a dimension ranging from 30–70 nm with an average of 50 nm. The effect of these ZnO nanoparticles as cure activator was studied for the first time in natural rubber (NR) and nitrile rubber (NBR) and compared with conventional rubber grade ZnO with special reference to mechanical and dynamic mechanical properties. From the rheograph, the maximum torque value was found to increase for both NR and NBR compounds containing ZnO nanoparticles. ZnO nanoparticles were found to be more uniformly dispersed in the rubber matrix in comparison with the conventional rubber grade ZnO as evident from scanning electron microscopy/X‐ray dot mapping analysis. The tensile strength was observed to improve by 80% for NR when ZnO nanoparticles were used as cure activator instead of conventional rubber grade ZnO. An improvement of 70% was observed in the case of NBR. The glass transition temperature (T_g) showed a positive shift by 6°C for both NR and NBR nanocomposites, which indicated an increase in crosslinking density. The swelling ratio was found to decrease in the case of both NR and NBR, and volume fraction of rubber in swollen gel was observed to increase, which supported the improvement in mechanical and dynamic mechanical properties. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007