Study of the corrosive effect of ozone on vulcanizates

Objectives. The work sets out to model the ozone corrosion of vulcanizates as a percolation phase transition, similar in the scheme of development of continual percolation on a plane, during which the growing regions of the new phase form a single “spanning” cluster. In this case, the continuity of the sample is broken, being divided into two parts. In the presented model, the ozone corrosion process is divided into two stages. At the first stage, ozone corrosion of the material occurs mainly along the perimeters of already ozonized surface areas, which leads to their growth and subsequent merging. Upon contact of adjacent surface areas consisting of ozonolysis products loaded with two-dimensional tension, corrosion cracks begin to appear on the surface. At the second stage of the corrosion process, corrosion cracks that grow deeply into the material due to its stress state lead to the penetration of ozone into the internal regions of the sample. The article presents the results of computer-simulation and real experiments carried out on ozone corrosion of technical vulcanizates in a plane stressed state.

Methods. Computer simulation of the time dependence of the total contact length of the areas of ozone corrosion products and the initial vulcanizate was carried out using a C++ program developed by the authors. Real experiments were carried out on a TOM-1000 setup. Samples for research by the TOM (technical ozone resistance of materials^[1]) method comprise thin disks, which are clamped along the contour and subjected to one-sided two-dimensional tension by compressed air pressure. From the side of the opposite plane, the sample is exposed to the ozone flow. The installation makes it possible to create in the sample a relative deformation of up to 100% increase in the surface area.

Results. Computer simulation allowed, in combination with direct measurements of the time dependence of ozone absorption, the dynamics of the destruction of vulcanizates in an ozone environment to be investigated. A numerical parameter of the ozone resistance of vulcanizates—the coefficient of ozone resistance—is proposed. This coefficient is almost linearly related to the time before the onset of cracking, but it is more accurate because it does not require visual observation of the ozonolysis process.

Conclusions. The results of computer simulation are in good agreement with the results of real experiments.

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