Avaliação de óleo vegetal natural e epoxidado em composições elastoméricas para banda de rodagem

Abstract

The incorporation of vegetable oils into the development of tread rubber formulation has been one of the alternatives to reduce the use of oil with high contents of aromatic polycyclics. Many studies suggest the substitution of aromatic oil by vegetable oil extracted from palm and soybean, and other studies propose that vegetable oils have reactive characteristics capable of promoting activation in vulcanization reaction. In this work, vegetable soybean oil was investigated as a lubricant / plasticizer and also as co-activators in natural rubber compounds vulcanized by sulfur, in natural state and chemically modified, through the epoxidation of soybean. The characterization of the natural and epoxidized soybean oil was carried out by Fourier Transform Infrared (FTIR) and Nuclear Magnetic Resonance with Protons (1H-NMR) spectroscopy. A standard formulation was used and from the other 5 mixtures were made with aim of replacing the aromatic oil and the stearic acid with the vegetable oil samples, a white sample, without the System was also prepared. The compositions were processed in a closed Banbury mixer and after the homogenization was performed in a cylinder. The curing properties were evaluated on an oscillatory disk rheometer, and the non-vulcanized characteristics by a Mooney viscometer and a rubber processing analyzer (RPA). The physical-mechanical properties were evaluated through the tests of hardness, density, tensile strength and tear and abrasion, as well as crosslink density. FTIR analysis confirmed a typical structure of an ester derived from soybean oil and the appearance of bands indicating the presence of epoxy groups. The physico-mechanical properties presented satisfactory results when the vegetable soybean oil was used as a lubricant / plasticizer and could be a substitute for the aromatic oils, thus guaranteeing the reduction of aromatic polycyclics. The evaluation of the white sample indicated the need for activators for the vulcanization reaction, since it presented inferior properties when compared to the standard, probably caused by the inefficient formation of cross-links. The effect of vegetable oil as a co-activator can be verified, even promoting better dispersion, detrimental has hampered the formation of cross-links when compared to the standard causing low mechanical properties.