Migration of Antioxidants and Accelerators in Natural and Synthetic Rubber II. Sulfenamide System Studies and Comparison of Age Resister Migration under Inert and Practical Conditions

Abstract

Abstract Radiochemical techniques developed for studying extender oil migration in various elastomers have been adapted for use in investigating the migration of age resisters and curatives. This paper contains basic diffusion coefficient data for nine compounds including both staining and nonstaining antioxidants and members of the sulfenamide, thiazole and thiuram accelerator series. Techniques for synthesizing these age resisters and curatives in the carbon-14 and sulfur-35 labelled form are described. Migration was studied in natural rubber, SBR, cis-polybutadiene and EPT vulcanizates. Computer techniques were used to calculate diffusion coefficients from radiochemical count data. Results from preliminary migration studies under practical curing and end-use conditions are also presented. In the case of phenyl-2-naphthylamine migration in cis-polybutadiene, a pronounced decrease in diffusivity with increasing surface area of the carbon black filler was observed.