Migration behaviors of wax to surface in rubber vulcanizates

The migration behaviors of wax to the surface in rubber vulcanizates were studied using natural (NR), styrene–butadiene (SBR), and butadiene rubber (BR) vulcanizates. The migration experiments were performed in a convection oven at 60 and 80°C for 14 days. There were less than 10% of the normal alkanes of n-C22H46 to n-C38H78 that migrated to the surface in the vulcanizates and evaporated at 60°C for 14 days. The amount of normal alkanes that migrated to the surface in the vulcanizates and evaporated at 80°C for 14 days was decreased by increasing the molecular weight of the normal alkanes. The migration of the normal alkanes in the NR vulcanizate was more sensitive to the variation of the molecular size of the normal alkanes than those in the BR and SBR vulcanizates. The migration behaviors of the normal alkanes in the vulcanizates were very similar to their evaporation behaviors. Major factors influencing the migration behaviors of the wax were discussed using the calculations of structures of the normal alkanes and evaporation experiments of wax.