Prevulcanization inhibitor of sulfur-free thiuram vulcanization

On the basis of Mooney scorch measurements at 120°C and of continuous measurements of vulcanization in a Vuremo curemeter at 145°C, sulfenamides which function as inhibitors of the sulfur-free thiuram vulcanization have been investigated. It was found that the actual prevulcanization inhibitor is 2-mercaptobenzothiazole. Its formation from sulfenamides is activated by zinc dimethyldithiocarbamate since the vulcanization of rubber by thiuram disulfides in the presence of zinc oxide is always accompanied by the formation of zinc dithiocarbamate. It seems probable that the inhibition effect of 2-mercaptobenzothiazole is attributable to the formation of a complex with zinc dimethyldithiocarbamate which decreases the reaction rate in the initial steps of the sulfur-free thiuram vulcanization and thus causes the scorch delay.     

Contribution to the mechanism of sulphur-free thiuram vulcanisation

The influence of the concentration of tetramethylthiuram disulphide on the kinetics and degree of the sulphur-free vulcanisation of pale crepe in the absence and in the presence of thiourea has been investigated. Rate and degree of the vulcanisation increase with concentration of tetramethylthiuram disulfide to a certain limit. Exceeding this limit the values of the rate constant and the crosslinking density decrease. Due to the presence of thiourea the rate of the vulcanisation is increased and the final degree of vulcanisation is decreased. This effect of thiourea also depends on the concentration of tetramethylthiuram disulphide. On the basis of the above results the mechanism of the tetramethylthiuram disulphide vulcanisation is discussed.     

Catalytic Partial Oxidation of Biomass/Oil Mixture

Investigation was focussed to application of waste POX （partial oxidation）, e.g., meal rape in form of suspension in high boiling hydrocarbons from crude oil distillation. There is an opportunity for utilization of biomass waste resulted from fuels bio-components production. A decrease of oxygen and water steam demand in feed for POX process was observed in this variant. Catalytic effect of iron nanoparticles or nickel nitrate as catalysts in improvement of the pilot plant biomass/oil partial oxidation was investigated as well. Presence of catalyst in the feed supports formation of carbon monoxide and suppression content of methane in the gas product. Experimental data were well compared with process simulation based on eauilibrium reactor model.     

Theoretical Structure Determination of a Complex Material: κ-Al2O3

The atomic and electronic structures of kappa-Al₂O₃ are determined using theoretical first-principles techniques based on density-functional theory (DFT), plane waves, and pseudopotentials. The obtained structure is confirmed by analysis of powder X-ray diffraction data. The structure is orthorhombic with oxygen ions in close-packed ABAC stacking and aluminum ions occupying both tetrahedral (1/4) and octahedral (3/4) interstitial sites. A growth model for chemical vapor deposition of kappa-Al₂O₃ is proposed based on the atomic structure. Calculated electronic structure and charge density yield a band gap of 5.3 eV and a high ionic character of the bonds. The study shows the applicability of DFT-based methods to complex and metastable materials.     

Telomerase Interaction Partners–Insight from Plants

Telomerase, an essential enzyme that maintains chromosome ends, is important for genome integrity and organism development. Various hypotheses have been proposed in human, ciliate and yeast systems to explain the coordination of telomerase holoenzyme assembly and the timing of telomerase performance at telomeres during DNA replication or repair. However, a general model is still unclear, especially pathways connecting telomerase with proposed non-telomeric functions. To strengthen our understanding of telomerase function during its intracellular life, we report on interactions of several groups of proteins with the Arabidopsis telomerase protein subunit (AtTERT) and/or a component of telomerase holoenzyme, POT1a protein. Among these are the nucleosome assembly proteins (NAP) and the minichromosome maintenance (MCM) system, which reveal new insights into the telomerase interaction network with links to telomere chromatin assembly and replication. A targeted investigation of 176 candidate proteins demonstrated numerous interactions with nucleolar, transport and ribosomal proteins, as well as molecular chaperones, shedding light on interactions during telomerase biogenesis. We further identified protein domains responsible for binding and analyzed the subcellular localization of these interactions. Moreover, additional interaction networks of NAP proteins and the DOMINO1 protein were identified. Our data support an image of functional telomerase contacts with multiprotein complexes including chromatin remodeling and cell differentiation pathways.     

Stabilization/solidification of galvanic sludges by asphalt emulsions

A combination of two-aqueous asphalt emulsions was proposed for stabilization/solidification treatment of galvanic sludges prior to landfilling. The presented procedure comprises mixing the galvanic sludge with a slow setting nonionic asphalt emulsion and subsequently forming a secondary asphalt barrier by means of a rapid setting anionic asphalt emulsion. The method was tested on four samples of galvanic sludge from various galvanizing plants, with various water and pollutant contents. Stabilization efficiency was assessed by water-leaching test, TCLP test and by determining ecotoxicity of leachates. Leachate parameters exhibited very low values and favorable results of ecotoxicological tests indicate high efficiency of the developed procedure for galvanic sludge disposal.     

Effect of high-abrasion furnace carbon black on the course of thiuram-accelerated sulfur vulcanization

The effect of high-abrasion furnace (HAF) carbon black on the course of the tetra-methylthiuram disulfide-accelerated sulfur vulcanization of natural rubber has been investigated at temperatures from 100°C to 140°C. Continuous measurements in a Vuremo curemeter were used to estimate the extent of crosslinking, which was plotted against cure time. Results now available show (1) HAF carbon black does not alter the mechanism of the thiuram-accelerated sulfur cure; it also has no qualitative effect on the kinetics of the vulcanization reactions involved. (2) Quantitatively speaking, essential differences take place. The rate constants of vulcanization rise considerably when HAF carbon black is used; there is a dependence on the HAF carbon black content of the rubber compound. Yet the activation energies of vulcanizations are practically the same as in carbon black-free mixture, amounting to about 31 kcal/mole. (3) Measurements of the course of vulcanizations prove the reinforcing effect of HAF carbon black.     

Stabilization/solidification of munition destruction waste by asphalt emulsion

Destruction of discarded military munitions in an explosion chamber produces two fractions of hazardous solid waste. The first one is scrap waste that remains in the chamber after explosion; the second one is fine dust waste, which is trapped on filters of gas products that are exhausted from the chamber after explosion. The technique of stabilization/solidification of the scrap waste by asphalt emulsion is described in this paper. The technique consists of simple mixing of the waste with anionic asphalt emulsion, or two-step mixing of the waste with cationic asphalt emulsion. These techniques are easy to use and the stabilized scrap waste proves low leachability of contained heavy metals assessed by TCLP test. Hence, it is possible to landfill the scrap waste stabilized by asphalt emulsion. If the dust waste, which has large specific surface, is stabilized by asphalt emulsion, it is not fully encapsulated; the results of the leaching tests do not meet the regulatory levels. However, the dust waste solidified by asphalt emulsion can be deposited into an asphalted disposal site of the landfill. The asphalt walls of the disposal site represent an efficient secondary barrier against pollutant release.     

Effect of temperature on the course of thiuram-accelerated sulfur vulcanization

Tetramethylthiuram disulfide-accelerated sulfur vulcanization of styrene-butadiene rubber has been investigated at temperatures from 100°C to 170°C over 0.5 to 600 min. Continuous measurements in a Vuremo curemeter were used to estimate the extent of crosslinking, which was plotted against cure time. Apart from the induction period (t_i), the kinetic graphs are satisfactory represented by a rate equation assuming three independent first-order reactions: fast crosslinking, degradation, and slow crosslinking. The rate equation contains seven kinetic parameters. Over the temperature range studied, there is no difference between the values of activation energy for t_i^?1, for fast crosslinking, and for degradation. The activation energy of slow crosslinking only is significantly greater. Due to the presence of Aerosil, the reciprocal values of the induction periods and the values of the ultimate extents of fast crosslinking are increased, and the values of the rate constants of degradation and slow crosslinking are decreased. Simultaneously, the activation energy of slow crosslinking is also significantly decreased. On the basis of these results, the proposed theory of tetramethylthiuram disulfideaccelerated sulfur vulcanization supposing that zinc dimethyldithiocarbamate is the actual accelerator in this type of curing system is discussed.     

Hydrodynamic behaviour and oxygen transfer rate in a pilot plant fermenter: I. Influence of viscosity

The effects of varying impeller speed, aeration rate and viscosity on mixing time, power consumption and oxygen transfer rate were studied in the pilot plant fermenter. The rheological behaviour of erythromycin fermentation broth was simulated by colloidal starch solutions at apparent viscosities of 0.02–0.20 Pa/s. The volumetric oxygen transfer rate coefficient was determined by the sulphite and static method. The experimental results showed that at low viscosities, up to of 0.02 Pa/s, the suitable range of impeller speed is 250–300 min^?1 at aeration rate 0.6–0.8 VVM from the point of view of power input (2.6–2.8 kW/m³) and sufficient coefficient K_La (160–200 h^?1). At viscosities higher than 0.02 Pa/s (with pseudoplastical character) the suitable range of impeller speed is 300–350 min^?1 at the same aeration rate. Then the power input for mixing is 3.0–3.5 kW/m³ and the coefficient K_La ～ 50 h^?1.