Influence of the Type of Vulcanizing System on the Properties of Water-Swellable Rubbers

Abstract

The work was the first to study the influence of standard sulfur and sulfur-free (including a sulfur donor) effective vulcanizing systems on the complex properties of water-swelling rubbers based on NBR (BNKS-28 AN) rubber and Na-carboxymethylcellulose as a water-swelling reagent. The methodological approach used is based on the possibility of purposefully varying the type of cross-links, as well as the cross-linking density. This, in turn, determines the characteristics of rubber swelling upon contact with water, which is important when developing formulations for water-swelling seals of packer equipment. The article presents data from rheometric studies, assessments of the mechanical characteristics of rubbers and their ability to swell in an activation medium (water at 23±2 °C), as well as calculations of the total, chemical and physical cross-link densities. It has been established that with an increase in the sulfur/CBS ratio from 1,0/1,5 to 4,0/6,0, the value of the chemical crosslink density increases from (0,79 to 3,48)·10^-3 mol/cm³. For an effective vulcanizing system, when the content of the components of the vulcanizing system CBS/TMTD/DTDM from 0,5/1,0/0,67 to 1,5/3,0/2,0 the value of the chemical crosslinking density parameter varies from (0,48 to 1,14) ·10^-3 mol/cm³. This causes a change in the swelling ability of elastomers and better preservation of the elastic-strength properties of materials in the swollen state. It has been revealed that with certain variants of standard and effective vulcanizing systems, close values of chemical and physical cross-link densities are achieved, which ensures similar physical and mechanical properties of rubbers, as well as their behavior when exposed to an activation fluid.