Effect of Carbon Black Densification on Structure Measurements

Abstract

A simple method of pretreating carbon black has been developed which permits measurements to be made on the dry carbon black which reflect on the basic property called “structure.” Correlation between these measurements and extrusion shrinkage of raw stocks is demonstrated. With a small surface area adjustment, this correlation is believed to be as reliable as extrusion shrinkage values.

A General Correlation Between Treadwear and Carbon Black Properties

“…The CTAB specific surface area and 24M4-DBP absorption methods have been described in previous publications [4,5]. Detailed laboratory procedures are available from the authors on request.…”

“…The result is a measured surface which, in essence, corresponds to the surface accessible to rubber and thus more nearly governs reinforcement than the total specific surface area measured by the classical nitrogen adsorption test, or the iodine adsorption, which is influenced by carbon black surface chemical characteristics [4]. The second advance in carbon black characterization is a compression procedure applied to carbon black prior to evaluation of vehicle demand by the standard dibutylphthalate absorption (DBP) test for &dquo;structure&dquo; [5]. The effect of this precompression is to reduce or eliminate the effects of densification history on the DBP value, thereby providing a more realistic measure of primary structure.…”

Reinforcement of Elastomers by Particulate Fillers

“…It has been found that subjecting the black to high pressure before measuring its vehicle demand tends to equalize the between-aggregate packing density [14]. When a moderately viscous vehicle, e.g., dibutylphthalate (DBP), is added gradually to dry carbon black in an internal mixer fitted with a device measuring the torque on the mixer blades, no appreciable torque is developed until the interstices between carbon black particles are filled with vehicle.…”

“…If occluded rubber is, indeed, shielded from deformation, then the fraction of the total mass capable of undergoing large reversible deformation must be decreased by occlusion of part of the rubber [50]. Extrusion shrinkage is also affected by specific surface area, and cognizance has been given to this variable by applying a correction to empirical structure-shrinkage correlations [14]. 4b).…”

Structure–concentration equivalence in carbon black reinforcement of elastomers. III. Application to tensile strength

“…The st'ructure "shift factor" a shows excellent correlation with the standard dibutyl phthalate (DBP) absorption test for structure, but appears to be linearly related to the DBP value of carbon black following repeated static compression t:, 24000 psi, as recommended by Dollinger, Kallenberger, and Studebaker. 6 Relative to an arbitrarily chosen reference black, a = (24 + A)/(24 + Ad (2) where A is the DBP value of the subject carbon black and A, is the corresponding value for the reference black, both determined by the precompression procedure.…”