Comparative Assessment of Ozone and Weather Aging of Rubber by Laboratory and Field Testing Conditions

Abstract

The authors compared the results of determining the ozone resistance (OR) and weather resistance (WR) obtained in laboratory and natural conditions of tropical climate. The samples were manufactured with unsaturated rubbers (nitrile butadiene rubbers BNKS-18AN, BNKS-28AN, BNKS-40AN and SKN-26PVC-30, styrene butadiene rubber SKMS-30 ARKM, isoprene SKI-3 and butadiene SKD-ND). All the samples were not filled with antioxidants or antiozonants. The curing process at 160 °C and the total crosslink density (νt) were studied using a MonTech MDR 3000 Professional rotorless rheometer. The physical and mechanical properties of the vulcanizates were determined with the using of a Zwick\Roell Z010 tensile testing machine at a test speed of 500 mm / min. Hardness and tear resistance were also determined. The numerical estimate of νt was obtained from the data on the dynamic shear modulus. Density of chemical bonds νch was determined from the data of equilibrium swelling in toluene according to the Flory-Rener equation. Full-scale climatic tests in tropical climate in the south of the Republic of Vietnam were carried out for 9 months in accordance with GOST 9.066-76 with initial deformations of 10, 20, 30, 40 %. The sample stand was oriented south, at a 45 degree angle. Cracks formed on the rubber surface were recorded by photography. The time before the onset of fracture Tof and the time until the appearance of the first cracks Tfc were determined. It is shown that samples of rubbers with high OR in laboratory tests had the best WR. A correlation of νch with Tof and Tfc was revealed. The obtained results show the possibility of using the express method for assessing the OR of rubbers in the development of formulations for tropical climates.