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Abstract

A method for preparation of a dual phase filler for elastomers for manufacturing technical rubber items, including such for microwave protection. The method involves the following stages: first stage—1/10 of the silicasol impregnating solution obtained by its dilution in distilled water at a 1:10 ratio is pulverized over the carbon black at constant stirring; second stage—the carbon black pulverized with the silicasol impregnating solution is let stay in air at room temperature for 24 hours; third stage: a two-step thermal activation in a drying cabinet is carried out—at first at 80° C. for 2 hours, and then at 250° C. for 2 hours; fourth stage—9/10 of the impregnating solution that remained from the first stage is pulverized successively over the already impregnated carbon black at constant stirring. It again is let stay for 24 in air at room temperature; fifth stage: a three-step thermal activation in a drying cabinet is carried out—at first at 80° C. for 2 hours, then at 150° C. for 4 hours and finally at 250° C. for 4 hours. The dual phase filler includes SiO₂ in amounts 1 to 10% and carbon black 90 to 99%. It has the following parameters: specific surface area /BET/−20-50 m²/g, Iodine adsorption number—15-30 mg/g, Oil absorption number—50-90 ml/100 g, mesopore volume—0.05-0.20 cm³(STP)/g, mesopore diameter—10-20 nm. According to the invention the advantages ensured by the method are in the implementation of a multistage thermal activation at not very high temperature; in yielding improved texture of the dual phase filler obtained and in better insulation of the carbon black aggregates by the silica phase.

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