INFLUENCE OF PLASTICIZERS WITH OXYGEN-CONTAINING HETEROCYCLES ON THE STABILITY OF PROPERTIES AND SORPTION CAPACITY OF HIGHLY FILLED SWELLABLE RUBBERS

HRFWPH

Abstract

The study is aimed at elucidating the influence of plasticizers containing oxygen-bearing heterocycles on the stability of physicomechanical properties and the swelling behavior of highly filled rubbers based on butadiene–nitrile rubber. As a swelling filler, an industrial product – sodium carboxymethylcellulose (NaCMC) with a particle size of 0.5–1.0 mm – was employed in an amount of 150 phr per 100 phr of rubber. Compounds with oxygen-containing heterocycles of different reactivity, namely Oxal T-92 (a compoud of substituted dioxane alcohols) and epoxidized soybean oil (ESO), were used as plasticizers. Hansen solubility parameter calculations demonstrated that the studied plasticizers exhibit good compatibility with both the rubber matrix and the swelling filler. It was established that the plasticizers reduce the Mooney viscosity of the rubber compound, lower both maximum and minimum torque values, and increase the time required to reach optimum vulcanization. The introduction of 30 phr of plasticizers was shown to reduce the tensile strength of the rubbers by approximately 20%, which is attributed to the weakening of intermolecular interactions. A difference in the effect of Oxal T-92 and ESO dosage on the tensile strength of rubbers was revealed: with increasing ESO content, tensile strength improves due to the ability of epoxy groups to interact with hydroxyl groups of the swelling filler, whereas with increasing Oxal T-92 content, tensile strength decreases. Exposure of rubbers to oil and aqueous media of various mineralization levels (formation water, alkaline, and acidic solutions) demonstrated that the swelling behavior depends both on the nature of the medium and on the type of plasticizer. A more pronounced swelling tendency was observed for rubbers containing Oxal T-92. The optimal dosage of plasticizers, providing the maximum effect in terms of both swelling capacity and processing characteristics, was found to be 30 phr per 100 phr of rubber.