Fraction Scaling and Dynamical Properties of Elastomer Materials

Scaling of the real and the imaginary part of dynamic moduli with frequency, for fully cured elastomer materials as gum and active carbon black filled butyl rubbers, is considered experimentally and theoretically. For gum rubber in different ranges of frequency complete agreement with G''-scaling predicted by the Rouse theory is obtained. Obtained slopes for all G' and G'' of filled rubber are much lower.

Phase topology of a NR/BR elastomer blend with active filler

The relations between the structure and mechanical properties of a polymer blend of natural (NR) and polybutadiene (BR) rubber (i.e. a NR/BR blend with the weight ratio of the components 70/30) filled with active carbon black were analysed. The properties of the individual phases in the blend were resolved by modeling the stress-strain relationship according to the Bauer procedure for high extensions. The obtained results indicated that BR is the dispersed phase, having a higher modulus, which was also confirmed by the much better fit of the experimental data to the series type of phase coupling according to the Takanayagy theory.

Catalytic Oxidation of Substituted Phenols in a Trickle Bed Reactor

The catalytic wet oxidation was studied of phenol, 2-aminophenol, salicylic acid and 5-sulfosalicylic acid performed in a laboratory trickle bed reactor. A three-phase high-pressure catalytic reactor with an inside diameter of 18 mm and length of catalytic bed of 200 mm was operated at temperatures 90-180 °C, pressures 2-7 MPa and liquid space velocity 1-10 h-1. Simultaneously, the catalytic activity and the stability of extruded active carbon black Chezacarb and active carbon Chemviron were tested. At a comparable activity, the active carbon Chemviron exhibited a greater mechanical strength and stability. The influence of phenol substituents on the oxidation conversion corresponded to their inductive effect: The electropositive amino group supported the oxidation, on the contrary, the presence of carboxy and sulfo groups on aromatic ring led to only low conversion. The complications on evaluating the experimental data are caused by the non-isothermal temperature profile along the catalyst bed, the non-ideal oxygen dissolution in aqueous solutions and especially the hydrodynamic effect of flow rate on the degree of catalyst wetting and thus on the entire effectiveness of the oxidation process.

Catalytic Effect of Active Carbon Black Chezacarb in Wet Oxidation of Phenol

The catalytic effects of hydrophilic granulated active carbon black Chezacarb have been tested in the oxidation of dilute (5 000 ppm) aqueous solutions of phenol. The research was focused on combined utilization of sorption and chemical (oxygen functional groups) properties of carbon black which support formation of free radicals in oxidation and on the catalytic effects of metals (Fe, Ni and V) present in the sorbent mentioned. The oxidation was carried out in a stainless steel autoclave of 1.25 l capacity. The reaction temperatures and the total pressures varied in the intervals of 120-160 °C and 3-5 MPa, respectively. The reaction mixture was analyzed by means of HPLC with UV detection (254 nm). The experimental data were evaluated by means of the ASPEN PLUS 9.2 program. The model of laboratory autoclave involved the reaction kinetics as well as the phase equilibria and dissolution of oxygen and carbon dioxide in the reaction mixture. Although the active carbon black shows a lower catalytic activity than the usual copper catalyst in the wet oxidation, it has the advantage of avoiding the undesirable releases of heavy metals in waste waters, which escapes accompany the application of copper catalysts.

The Theory of Rubber Reinforcement: Interaction of Carbon Black with Sulfur and Rubber

Active channel black combines chemically with sulfur when heated with sulfur solutions. The amount of sulfur combined increases after hydrogenation of the carbon black. The dimensions of the carbon black aggregates increase as the result of the reaction with sulfur. Hydrogenation of channel black increases the content of insoluble rubber in the carbon-rubber gel formed during milling of a rubber-carbon black mixture. Hydrogenation of channel black increases the content of bound sulfur, the modulus, and tensile strength, in comparison with vulcanizates containing the original unhydrogenated channel black. These facts suggest that active carbon black enters the composition of the vulcanizate structure, and this is a factor in rubber reinforcement.

Dispersion of Fillers in Rubber

The activity of a filler in rubber depends on the size and geometrical shape of the particles, and on their chemical constitution. The smaller a particle is, the larger is the total surface area of the filler per unit weight. If, for example, the diameter of a particle of an active carbon black is 30 mµ, the total surface area is about 100 sq. m. per gram. If the particle diverges from spherical shape and has a crystalline form, the surface area is greater, as the relation of the area of a sphere to that of a cube of equal volume clearly shows (surface area of sphere: surface area of cube = 12.5:15.6). Furthermore, corners and edges are present on a particle of crystalline shape, which are particularly active according to the experimental results of interface physics. By means of this phenomenon, the differing activity of various fillers of equal particle diameter can be explained.