Utilization of Biodiesel as Plasticizer for Tread Compound of SBR Tire

The solubility parameter of a group of methyl esters of fatty acids, the main components of biodiesel, was calculated using the group incremental method proposed by Van Krevelen. The solubility parameter of biodiesel was compared with that of a series of rubbers like EPDM, butyl rubber, polyisoprene, polybutadiene, SBR (with different content of styrene) and nitrile rubber (with different content of acrylonitrile) and it was shown that biodiesel is an effective solvent for all the above rubbers, except nitrile rubber. The solubility experiments being carried out manifest Polyisoprene; Polybutadiene and SBR are easily soluble in biodiesel, while Polystyrene is not, gives a cloudy solution. Considering on the solubility parameter of biodiesel and those of the above rubbers, it was concluded that biodiesel is able to behave as an internal lubricant in the matrix of diene rubbers. The same situation occurs with the common aromatic mineral oil plasticizer known as T-RAE. The experimental evaluation of biodiesel used as plasticizer in an SBR based rubber compound have led to the conclusion that biodiesel is reactive with the sulphur curing agents,subtracting Sulphur to the crosslinking Polymer chains and leading to vulcanizate with lower moduli, tensile and hardness and higher elongation in comparison to reference compound fully plasticized with an aromatic mineral oil. Moreover, it is expected that biodiesel to be a good low temperature plasticizer because the low elastic modulus observed is desired in a winter tire tread for a good grip on snow and ice. The present work is only an exploratory work, and the tire tread formulation with biodiesel was not optimized.