27:T555,

The effect of hydrophilic additives – MC-2000 methyl cellulose and sodium polyacrylate – on the properties of a vulcanisate based on Neoprene W was studied. The rubber mixes were prepared in two stages: at the first stage, hydrophilic additives were introduced into the rubber; at the second stage, the remaining ingredients were introduced. Vulcanisation was carried out at a temperature of 150°C for 30 min. The viscosity of the rubber mixes, M, was measured at 120°C on an MVR 3000 Basic viscometer (MonTech), and the vulcanisation characteristics and vulcanisation rate, v, were measured on an MDR 3000 Basic rheometer (MonTech) at 170°C in accordance with ASTM D2084-79. From the results of these measurements it follows that, with the combined use of methyl cellulose and sodium polyacrylate, there is a synergistic reduction in M and in the vulcanisation rate of the rubber mixes. A vulcanisate containing both hydrophilic additives possesses the best hydrosorption properties and has satisfactory physicomechanical properties (nominal tensile strength, elongation at break, hardness, and tear strength). The values of these properties and their changes on exposure of the vulcanisate to distilled water (70°C, 24 h) meet the requirements laid down for water-swelling rubber sealing elements.

28:T47f,

Optical microscopy was used to investigate features of morphological transformation during the mechanical degradation of unfilled vulcanisates of nitrile butadiene rubbers in a thin mill roll gap and subsequent thermal treatment – revulcanisation without the addition of any components into the degradate. An analytical complex based on a Leica DM-2500 optical microscope, a Leica DFC-420C high-resolution digital colour camera, and a specialised computer desk was used. The influence of the milling time in the 0–40 min range on the morphological parameters and the nature of the fine structure of plasticised specimens was studied. The mechanisms of degradation and structure formation during the plasticisation of vulcanisates were analysed. The formation of an additional three-dimensional skeleton in ‘secondary’ vulcanisates and the build-up of this process with increase in the treatment time of the degradate were found, which may lead to an increase in the mechanical properties to a level exceeding that of the initial vulcanisate. However, increase in compositional inhomogeneity may have an adverse effect on oil resistance.

29:T6b2,