Effect of metallic impurities on the gasification of graphite in water vapor and hydrogen

The catalytic effects of metallic impurities on the reactivity of graphite towards water vapor and hydrogen in the temperature range 25° to 1100°C have been investigated as a function of the oxidation state of the impurity. Iron, cobalt and nickel are active catalysts for the former reaction between 600° and 1000°C when the metal is kept in the reduced state by means of added hydrogen. Motion of the metallic particles on the basal plane surface of the graphite during the reaction leads to the formation of channels which with the smallest catalyst particles are oriented mostly in the 〈112̄0〉 directions. Vanadium and molybdenum are weak catalysts under these conditions, whereas copper, zinc, cadmium, silver, chromium, manganese and lead are inactive. When hydrogen is absent so that the metal remains in the oxidized state, the catalytic activity of all these impurities is low or negligible. The reaction of graphite with dry hydrogen occurs less readily but is again strongly catalyzed by metallic iron, cobalt and nickel. Manganese, chromium, molybdenum and vanadium show a slight catalytic effect in the hydrogenation reaction at temperatures around 1000°C, whereas copper, zinc, cadmium, silver and lead are inactive.     

Hydrogenation of synthetic cis‐1,4‐polyisoprene and natural rubber catalyzed by [Ir(COD)py(PCy3)]PF6

In the presence of chlorinated solvents, the catalytic complex [Ir(COD)py(PCy₃)]PF₆ (where COD is 1,5‐cyclooctadiene and py is pyridine) was an active catalyst for the hydrogenation of synthetic cis‐1,4‐polyisoprene and natural rubber. Detailed kinetic and mechanistic studies for homogeneous hydrogenation were carried out through the monitoring of the amount of hydrogen consumed during the reaction. The final degree of olefin conversion, measured with a computer‐controlled gas‐uptake apparatus, was confirmed by Fourier transform infrared spectroscopy and ¹H‐NMR spectroscopy. Synthetic cis‐1,4‐polyisoprene was used as a model polymer for natural rubber without impurities to study the influence of the catalyst loading, polymer concentration, hydrogen pressure, and reaction temperature with a statistical design framework. The kinetic results for the hydrogenation of both synthetic cis‐1,4‐polyisoprene and natural rubber indicated that the hydrogenation rate exhibited a first‐order dependence on the catalyst concentration and hydrogen pressure. Because of impurities inside the natural rubber, the hydrogenation of natural rubber showed an inverse behavior dependence on the rubber concentration, whereas the hydrogenation rate of synthetic rubber, that is, cis‐1,4‐polyisoprene, remained constant when the rubber concentration increased. The hydrogenation rate was also dependent on the reaction temperature. The apparent activation energies for the hydrogenation of synthetic cis‐1,4‐polyisoprene and natural rubber were evaluated to be 79.8 and 75.6 kJ/mol, respectively. The mechanistic aspects of these catalytic processes were discussed on the basis of observed kinetic results. The addition of some acids showed an effect on the hydrogenation rate of both rubbers. The thermal properties of hydrogenated rubber samples were determined and indicated that hydrogenation increased the thermal stability of the hydrogenated rubber but did not affect the inherent glass‐transition temperature. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4219–4233, 2006     

In‐situ polymerized phenolic resin for reinforcement of chloroprene and ethylene–propylene rubber vulcanizates

Phenolic resin (PF) was incorporated into rubbers by in situ polymerization at the vulcanization conditions of rubbers. The PF with a localized three‐dimensional network structure was formed in chloroprene rubber (CR), whereas the fabric PF was formed in ethylene–propylene rubber (EPDM). The study results showed that the PF phase was effective on reinforcing these rubbers. Depending on the morphologies of the formed PF phases, various rubber properties could be significantly enhanced. In the case of CR rubber, the tensile strength, tear strength, and modulus could be considerably enhanced, but the elongation and resilience properties were limitedly affected by PF addition. For EPDM rubber, all mechanical properties were improved, particularly the elongation, about 26% increase. The substantial improvements of mechanical properties of CR and EPDM rubbers were attributed to their morphology, high flexibility, moderate stiffness, and excellent bonding with rubber matrix. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Toughening of unsaturated polyester with rubber particles. Part I: Morphological study

The morphology of rubber-modified unsaturated polyester is described. In order to modify the particle-matrix interface, different rubbers were used; BFGoodrich Hycar liquid rubbers and high molecular weight rubbers. Blends of different compositions were prepared. The microstructure of the materials was investigated using transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The volume fraction and the particle size of the rubbers' second phase was determined by applying quantitative metallography. The volume fraction of the precipitated phase was higher than the amount of added rubber. Such blends show phase inversion above 35 wt% of rubber.     

Epoxidation of Unsaturated Rubbers with Alkyl Hydroperoxide using Molybdenum Compounds as Catalyst in the Reactive Processing Equipment

A novel approach to the epoxidation of unsaturated rubbers in a reactive processing equipment is presented for the first time in this paper. The effects of the structures of unsaturated rubbers and catalysts on the epoxidation reaction were examined. The experimental results show that the reactivity of three typical unsaturated rubbers follows the decreasing order: ethylene‐propylene‐diene rubber (EPDM) > butadiene rubber (BR) > styrene‐butadiene rubber (SBR). No obvious further oxidation side reaction occurs during the epoxidation of EPDM and BR, while SBR has a significant degradation during reaction. Moreover, investigation of the catalytic system composed of tert‐butyl hydroperoxide (TBHP) and three different molybdenum compounds reveals that a blue molybdenum compound (Mo‐b), which is the product of the reaction of hydrogen peroxide (30% aqueous solution) with an excess of molybdenum powder, gives the highest catalytic activity and the highest efficiency of TBHP.     

溶剂在交联硅橡胶中无限稀释扩散系数测定

气相色谱法测定溶剂与聚合物材料之间的相互关系是一个快速、准确、方便的方法，为此利用气相色谱法测定了小分子溶剂在不同交联剂含量的交联硅橡胶中的无限稀释扩散系数，并研究了交联剂用量对无限稀释扩散系数的影响，这为研究交联硅橡胶特性提供了新方法。     

Gamma radiation effect of polymethylvinylphenylsiloxane rubbers under different temperatures

The gamma radiation effect on polymethylvinylphenylsiloxane (PMVPS) rubbers is investigated by irradiation exposure of PMVPS rubbers to a maximum dose of 200 kGy in the temperature range 28–110 °C. Compared with unirradiated PMVPS rubber, the elongation at break of irradiated PMVPS rubber decreases while its elastic modulus increases with the increase of absorbed dose or radiation temperature. DSC, ATR‐FTIR, XPS, and ¹H‐NMR indicate that slight degradation and oxidation reaction occur during the irradiation of PMVPS. Solvent swelling and gel fraction study confirms that the crosslinking density of PMVPS rubbers increases gradually with increasing absorbed dose or radiation temperature. Therefore, radiation‐induced crosslinking of PMVPS is dominant reactions for the chosen dose or temperature range. Furthermore, synergistic effect exists in the high‐temperature radiation process for PMVPS rubbers. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45404.     

Surface modification of silicone rubber by ion beam assisted deposition (IBAD) for improved biocompatibility

We studied the preparation of antimicrobial silicone rubbers of improved interfacial strength, which could be formed with the ion beam assisted deposition (IBAD) technique for coating metallic or inorganic materials (silver (Ag), Copper (Cu), and Hydroxyapatite(HAp)/TiO₂) on the silicone surface. Those coating materials provide high product safety as well as outstanding antimicrobial activity. The deposition methodology is composed of pre‐etching with oxygen gas, vaporizing the coating materials, and post‐treatment with Ar ion. With the evaporation of the coating materials, the Ar beam was focused on the substrate to assist deposition. It was found out that the ion assisting depositions in the IBAD process give a prominent enhancement in adhesion between silicone rubbers and coatings of Ag and Cu. The HAp/TiO₂ coating layer was easily dissolved in aqueous saline solution. All deposited layers display high antimicrobial activities against Staphlococcus aureus (ATCC 6538) and Escherichia coil (ATCC 25,922), showing 99.9% reduction of bacteria, respectively. In a cytotoxicity test, the Ag and HAp/TiO₂ coated silicone shows a decrease of cytotoxicity, while the Cu coating leads to a slight increase of cytotoxicity. The result on the surface modifications of silicone rubber will be employed in further study for applications of medical or rehabilitation devices. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1095–1101, 2005     

金属氧化物对硅橡胶和氟硅橡胶耐热性的影响

着重研究了金属氧化物对甲基乙烯基硅橡胶、甲基苯基乙烯基硅橡胶、三氟丙基甲基乙烯基硅橡胶耐热性的影响。结果表明,Ｆｅ２Ｏ３、ＦｅＯ３／ＳｎＯ２、ＳｎＯ２、ＣｅＯ２等可以显著提高硅橡胶的耐热性;光电子能谱分析结果说明,ＳｎＯ２、ＣｅＯ２在热空气老化过程中从高价态被还原到低价态,发生了多个（或单个）电子转移的氧化还原反应,从而阻止了硅橡胶的热氧化自由基链增长,提高了硅橡胶的耐热空气老化性能。     

Hydrogenation of natural rubber using nickel 2-ethylhexanoate catalyst in combination with triisobutylaluminum

Kinetic studies for the homogeneous hydrogenation of natural rubber, in the presence of nickel 2-ethylhexanoate and triisobutylaluminum, have been carried out by monitoring the change in hydrogen pressure in a Parr reactor of fixed volume. ¹H-NMR spectroscopy provides the measurements of the extent of hydrogenation. The reaction kinetics, in the presence of a fixed amount of catalyst, showed an overall second-order kinetic with respect to [H₂] and [CC]. The reaction has a relatively low apparent activation energy of 26.0 kJ mol^-1 and is therefore suitable for the hydrogenation of natural rubber at ambient conditions to minimize side reactions. The impurities in commercial rubbers have a slight effect on the catalyst activity. © 1996 John Wiley & Sons, Inc.     

橡塑共混中橡胶相形态控制的研究进展——一种橡塑共混新技术

介绍了一种橡塑共混的新方法。该方法从橡塑共混中橡胶相形态调控的理论研究结果出发，研制出的粒径及其分布可控的纳米级全硫化粉末橡胶，它极易在塑料中分散，与不同塑料共混后可制成橡胶相形态可控的各种增韧塑料和全硫化热塑性弹性体。     

Investigation of an indirect GC method for the determination of water content of rubbers

A method is proposed for the determination of low levels of moisture in rubbers and other soluble polymers. The material for analysis is dissolved in an appropriate solvent and triethylaluminium is added to react with the water contained in the sample. The liberated ethane is analysed by a simple GC technique. The method is calibrated using an internal standard and by addition of known amounts of water. A series of natural and synthetic rubbers dried under varying conditions were found to have water contents in the range 0.01-2% w/w. Removal of proteinaceous material from natural rubber reduces the equilibrium water content of the stored rubber. Active hydrogen impurities in the rubbers are shown to interfere with the determination and consequently the observed water content must be assumed to represent the upper limit of water unless such impurities are known to be absent, or present only in negligible amounts.     

Studies on heterogeneous polymeric systems. II. Polyblends containing saturated rubbers

Saturated rubbers composed of ethylene–propylene or ethylene–vinyl acetate copolymers and terpolymers were used in the mass polymerization of high-impact styrene or styrene–acrylonitrile polyblends. Conventional polymerization procedures lead to blends of inferior mechanical properties. The cause for the poor performance was traced to the inability of the rubber-phase particles to preserve the desired size and particularity during processing. Polymeric blends of saturated rubbers having mechanical properties comparable to those obtainable with polybutadiene rubbers are prepared by (1) controlling the rubber-particle size during prepolymerization and (2) preserving such size by crosslinking and grafting of the rubber following phase inversion. Extensive crosslinking of the rubber in the final blend must take place prior to processing to resist rubber particle deformation and disintegration during mechanical working. Rubber vulcanization is realized by the presence of peroxides in the final stages of polymerization; pendant unsaturation in the rubber is also needed or helpful. The reactivity and number of unsaturated groups in the rubber must be controlled to avoid excessive grafting prior to phase inversion and to permit efficient crosslinking following phase inversion.     

Studies on heterogeneous polymeric systems. I. Influence of morphology on mechanical properties

Polybutadiene rubbers of well-defined and varying molecular weight were prepared by anionic polymerization and used in the preparation of mass-polymerized polystyrene blends. The particle size of the dispersed rubber phase was varied by (1) controlling the relative viscosity, at phase inversion, of the two liquid phases composed of polystyrene and polybutadiene in styrene monomer; (2) by varying the intensity of mixing, and (3) by adding preformed polystyrene to the prepolymer, prior to phase inversion. The mechanical and dynamic properties of the resulting blends are found to be determined mainly by the particle size of the dispersed rubber phase, independently from the method used to obtain such size. The weight fraction of rubber phase, rather than the weight fraction of rubber charged, is found to correlate with the blend modulus and may also affect its level of toughness. Low molecular weight rubbers are found capable of efficient blend reinforcement, if the excessively small rubber particle size obtained by conventional processes is enlarged by incorporation of preformed polystyrene prior to phase inversion.     

金属离子对DMC催化聚合聚醚制备反应的影响

研究了在双金属络合催化剂用于催化合成聚醚过程中 ,起始剂或催化剂可能带入的微量离子对聚合反应的影响。结果表明 ,金属离子是否使催化剂中毒与阴离子的种类有关。除ZnCl2以外 ,绝大部分盐酸盐均对催化反应起阻碍作用 ;不同的金属盐 ,使催化剂失活的能力有所不同 ,NaCl对催化剂的影响最大 ,当Na+质量分数为 3× 10 - 6 时 ,催化剂即失活 ,而Ca2 +和Mg2 +对催化剂的影响相对较小。硫酸盐对聚合反应的有害影响很小 ,而MgSO4 等有助催化作用     

Influence of Impurities and Oxidation on Hydroconversion of Waste Cooking Oil into Bio-jet Fuel

The influences of impurities and oxidation evolution of waste cooking oil on the preparation of bio-jet fuel via hydroconversion were studied. The hydrogenation active sites and acid sites were covered by heavy metals, sulfides, and basic nitrogen compounds, resulting in the increase of selectivity for bio-jet fuel by decreasing the selectivity of diesel, aromatics, and iso-alkanes. The effects of impurities, oxidation on the reaction pathway, and product distribution became more distinct with higher catalyst acidity. The evolution and variation of naphthalene, indan, and phenanthrene obtained from cyclic fatty acids influenced the properties of fuel or evoked the catalyst deactivation. This work will help to design new catalysts for selective conversion of waste cooking oil into bio-jet fuel.     

Effect of butyl rubber type on properties of polyamide and butyl rubber blends

Polyamide‐12 was blended with butyl rubber, bromobutyl rubber, and chlorobutyl rubber with and without a sulfur curing system. Mechanical properties for dynamically vulcanized blends generally exceed those made with no vulcanization. Chlorobutyl‐containing blends prepared by dynamic vulcanization have higher tensile strength and elongation at break values in comparison to those made from other butyl rubbers. For a variety of polyamide/rubber blends made by dynamic vulcanization, there is very little effect of rubber percentage unsaturation and Mooney viscosity on the mechanical properties of the blends. In chlorobutyl‐containing blends prepared by dynamic vulcanization, the swelling index values attributed to the rubber portion decrease as rubber content decreases, and it is likely that the polyamide phase completely surrounds the rubber particles at compositions exceeding approximately 25% polyamide. Swelling index results can be correlated with elongation at break values for similar blends. The results of differential scanning calorimetry suggest that the polyamide phase is not a neutral component in high shear mixing with butyl rubbers with or without curing agents. Rheological studies indicate strong non‐Newtonian behavior for all blends of polyamide‐12 with butyl rubbers. Scanning electron microscopy on polyamide‐12/butyl rubber blends indicates compatibility for butyl rubbers in the order of chlorobutyl > bromobutyl > butyl rubber. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 1423–1435, 2004     

EXAFS study on Pd–Pt catalyst supported on USY zeolite

Local structure around Pd and Pt in the bimetallic Pd–Pt catalysts supported on ultra stable Y (USY) zeolite (SiO₂/Al₂O₃=680) was investigated by an extended X-ray absorption fine structure (EXAFS) method during oxidation, reduction, and sulfidation. The Pt L III-edge EXAFS spectra showed that a new bond that was significantly different from Pt–Pt to Pt–Pd metallic bonds was formed in the bimetallic Pd–Pt (4:1) reduced catalysts supported on USY zeolite. This new bond may reflect the ionic properties of Pt through the Pt–Pd interaction. Furthermore this new bond survived sulfidation indicating that the bond has a cationic property and sulfur-tolerance property. The Pt–Pd ionic interaction in these catalysts allows some of the Pd metal to survive as metallic phase. The existence of this metallic phase under sulfidation condition may result in high activity of Pd–Pt (4:1) catalyst supported on USY zeolite in the aromatics hydrogenation.     

Mechanical properties of alternating copolymers of acrylonitrile and butadiene

The alternating copolymer was prepared from butadiene (BD) and acrylonitrile (AN) with ethylaluminum dichloride as a complexing agent and with vanadyl chloride as a catalyst, and was investigated to explain effects of composition and sequence distribution on the physical properties, especially the viscoelastic properties and the ultimate mechanical properties. In the unvulcanized state, the viscoelastic properties of the alternating rubber is not essentially different from the random one, except for a slight difference in the relaxation spectra. However, the vulcanized rubbers show different shift factors. The latter depends upon the glass transition temperature (T_g.) Since the alternating copolymer possesses a T_g lower than the random one, the nature of the alternating copolymer corresponds to that of the random copolymer having an AN content of 40%. The difference in dynamic properties can be expressed with the different shift factors. In the isofree-volume state or at the temperature T_g + 25°C, the rubbers having various acrylonitrile contents and various degrees of alternation exhibit almost the same dynamic properties. However, the strain at break of the alternating rubber is higher than that of the random one. The temperature of maximum strain increases with increasing degree of alternation. The alternating rubber shows higher stress at break than the random one. The stiffness of the chain of the alternating copolymer is smaller than the random copolymer; in other words, the molecular chain of the former is more flexible than the latter. It can be said that the alternating copolymer is an excellent rubber having high tensile strength and elongation at break.     

New ways to improve the damping properties in high‐performance thermoplastic vulcanizates

The incorporation of viscoelastic materials represents an effective strategy to reduce the vibratory level of structural components. Thermoplastic vulcanizates (TPVs) are a special type of viscoelastic material that combines the elastomeric properties of rubbers with the easy processing of thermoplastics. In the present work, we propose innovative ways to improve the damping properties of high‐performance TPVs by using rubbers with carboxylic functionalities. For that, TPVs from physical blends of carboxylated hydrogenated acrylonitrile butadiene rubber (XHNBR) and polyamide 6 (PA6) were prepared. The chain dynamics of different mixed crosslink systems containing peroxide, metal oxides and hindered phenolic antioxidants were investigated in order to find the most suitable strategy to design a high‐performance TPV system with upgraded damping properties. The results indicate that the damping performance of the TPV system can be tailored by controlling the type and magnitude of the bonding interactions between the mixed crosslink system and the XHNBR rubber phase. Therefore, this study demonstrates the potential of TPV systems containing carboxylic rubbers as high‐performance damping materials. © 2020 Society of Chemical Industry