Petrunka Malinova

Characterization of hybrid fillers based on carbon black of different types obtained by impregnation

The paper presents the investigations on obtaining dual phase fillers with preset silica content running a successful impregnation of two completely different types of conventional carbon black with silicasol. The hybrid fillers studied were characterized by atomic absorption spectroscopy and inductively coupled plasma–optical emission spectroscopy. The total pore volume, the average pore diameter, the specific surface area, the oil absorption number, and iodine adsorption of the fillers were also investigated. The distribution of both phases within the hybrid filler obtained and their interpenetration were investigated with scanning transmission electron microscopy-energy dispersive X-ray spectroscopy. The hybrid products obtained were investigated as reinforcing fillers of natural rubber-based composites. The results obtained show that the suggested impregnation with silicasol of conventional carbon black is a perspective method for preparation of carbon-silica dual phase fillers. The method provides an easy control over the quantitative ratio between the two phases. The fillers thus prepared do not change significantly the curing and mechanical characteristics of the vulcanizates, but improve their thermal aging resistance. The isolation of the carbon black aggregates by the silica phase, and the interpenetration of the two phases is a prerequisite to obtain elastomer composites of good mechanical and microwave properties suitable for producing of microwave shielding devices.

Effect of carbon–silica dual phase filler obtained by impregnation method on the properties of SBR-based composites

Styrene butadiene rubber (SBR)-based composites have been reinforced with carbon–silica dual phase fillers. The new type of reinforcing fillers have been obtained by an impregnation method used for introduction and deposition of a second silica phase over the surface of carbon black particles. The mechanical properties of SBR-based composites (applicable for passenger tread compounds) have been investigated. It has been found that the modulus at 100% of elongation and tensile strength of the composites reinforced with the dual phase fillers have increased considerably in comparison to those of the composites containing standard carbon black.

Microwave properties of natural rubber based composites containing carbon black-magnetite hybrid fillers

Abstract The paper presents the synthesis and characterization of a carbon black-magnetite hybrid filler. The complex study on the structure of the filler has shown the magnetite phase to be distributed both over the surface (inter-aggregately) and inside (intra-aggregately) the carbon black particles, thus forming a true hybrid material. The results from the investigations on the mechanical and microwave properties of natural rubber-based composites filled with the new hybrid filler have been also reported. They have been compared to those of a composite comprising the physical mixture of carbon black and magnetite (at the same ratio as in the hybrid filler). The determined microwave characteristics of the composite comprising the hybrid filler obtained reveal the possibility for its use in manufacturing elastomer-based microwave absorbers.

Effect of Silica Phase on Certain Properties of Natural Rubber Based Composites Reinforced by Carbon Black/Silica Hybrid Fillers

The paper reports on the effect that the silica phase has upon certain characteristics of hybrid fillers obtained via impregnation of two completely different types of conventional carbon black, namely oil absorption number, iodine adsorption, specific surface area, etc. The article also presents their dynamic mechanical and electrical properties, as well as the homogeneity of natural rubber based composites comprising those fillers. It has been found that, the silica phase, depending on its amount (3 or 7%), changes considerably both the main characteristics of the fillers (ash content, specific surface area, oil absorption number, iodine adsorption number, etc.) and their thermal behaviour. The increase in the amount of silica phase leads to a decrease of the storage modulus, while the mechanical loss angle tangent increases during the transition from the glass into rubbery state. The changes in those parameters are related first of all to the changes in the elastomer-filler and filler-filler interactions, to the mobility of elastomer chains and to the relaxation processes. The higher silica content, the higher the surface and volume resistivity of the composites are. On the other hand, the fillers homogeneity worsens depending on the grade of silica phase dispersion along the hybrid filler.

Preparation and Characterization of Natural Rubber Composites Comprising Conductive Carbon Black/Magnetite Hybrid Fillers Obtained by Impregnation Technology

ABSTRACT Hybrid fillers have been prepared of conductive carbon black/magnetite at various ratios of the phases: 90:10, 70:30, and 50:50. The fillers have been characterized and their effect on the curing, mechanical, electric, and dynamic properties of natural rubber–based vulcanizates has been also investigated. The macrohomogeneity of the composites has been evaluated by ohmic resistivity measurements and correlation analysis. It has been established that all properties studied are dependent on the ratio between the filler’s phases. Viewing their composition, we conclude that the hybrid fillers are expected to exhibit both high dielectric and magnetic losses and may find application in the manufacturing of microwave absorbers. GRAPHICAL ABSTRACT

Some Factors Determining the Volume Resistivity of Filled Natural- Rubber-Based Nanocomposites

In recent years, special grades of electroconductive carbon black have been developed to overcome the usage of large amounts of filler in the preparation of composites with desired electrical properties. Characteristic features of the novel carbon black are its superhigh specific surface area and structure, which are many times higher than those of conventional electroconductive carbon black. The present article reports on natural-rubber-based composites, filled with carbon black of superhigh specific surface area and structure. New results concerning the influence of change in the filler concentration, applied pressure, and temperature on the volume resisitivity of the composites are presented and discussed. It has been found that the new filler lowers the percolation threshold greatly and ensures very high electroconductivity at low content. The influence of applied pressure on the volume resistivity depends on whether the amount of filler used is sufficient to reach or pass the percolation threshold: when the percolation threshold is not reached, the volume resistivity increases with increasing pressure; after reaching the percolation threshold, the volume resistivity decreases with increasing pressure. With increase in temperature, the volume resistivity of the examined composites decreases. With increase in the degree of filling, the examined hysteresis decreases too. The results obtained for the new conductive rubber composites may be considered as a novel contribution in the field of polymer materials research.