INFLUENCE OF WATER ABSORPTION PROCESS ON PHYSICAL AND MECHANICAL PROPERTIES OF FREE COATING FILM

Implementation of modern internal polymer coatings of oil pipelines and pump-compressor pipes leads to a significant increase in the reliability and operational safety of fuel and energy complex facilities. Most vertically integrated oil companies have crossed the 50 % threshold for newly built pipeline fleet protected by internal coatings, and such companies as LUKOIL Western Siberia LLC and Surgutneftegaz OJSC have approached 100 %. However, there are still no implemented methods for diagnosing pipes with internal coatings (IC). In this regard, an important task is to predict the resource of internal polymer coatings of pipes. Laboratory research methods allow simulating the operating conditions of internal polymer coatings in a short time and with the least cost. Based on this, we can conclude that it is advisable to use various types of internal polymer coatings to resist the effects of a corrosive environment. One of the main factors in reducing the physical and mechanical properties of internal polymer coatings is the process of water absorption. Since this process occurs during the first day from the start of operation, further interaction with the environment and provision of barrier properties occur in a water-saturated state. As the experiment showed, significant differences in physical and mechanical properties are observed, the change of which is not taken into account when assessing and predicting the resource of internal polymer coatings. In a first approximation, the process of water absorption by a polymer coating can be described as follows: the process of adsorption of the components of the medium → diffusion penetration of the components of the medium into the coating layer → deformation of intermolecular bonds → the beginning of the process of destruction of the polymer. The results of the studies showed that there is a saturation limit of the free film of the polymer coating, which in the simulated conditions of the autoclave test is 20 days, after which this process stops. The most significant, from a practical point of view, result is a decrease in the glass transition temperature by 30 °C compared to the initial state. When selecting the maximum permissible operating temperature, the parameter Tg-30 °C can be considered as the first approximate one and then, taking this into account, plan a set of tests according to State Standard R 58346-2019.