Diffusion of amine stabilizers in vulcanized natural rubber compositions used in tires

The diffusion of amine stabilizers in vulcanized natural rubber formulation s used in tires was investigated. Experiments were undertaken using a "sand wich" system composed of a sample disk containing the additive (source disk ) between two external disks of nonadditivated rubber (reception disks). Di ffusion coefficients (D) were calculated from the experimental migration cu rves following the Boltzman-Matano model. Theoretical diffusion curves for the additives were obtained according to the limited extension source in an infinite medium. Experimental data showed reasonable fitting with the theo retical curves, suggesting that D does not depend on the additive concentra tion. Thermooxidative stability data for the vulcanized rubber containing t he additives showed no correlation to the diffusion process. (C) 2000 John Wiley & Sons, Inc.