Investigation of blooming on non black NR - based straps of rubber slippers

Abstract

Blooming is the appearance of powdery deposits on the surface of a rubber product. It occurs, whenever a rubber product contains an incompatible ingredient in excess of soluble quantity. Blooming is considered to be a major defect in rubber products. It spoils the smooth shiny rubber surface and impairs the aesthetic appeal of the product. Blooming can also aid passage of air to the rubber mass and thus can cause oxidative degradation of rubber molecules. Since this blooming phenomenon (defect) occurs very often in non - black Natural Rubber (NR) - based straps, the important tension - members of rubber slippers, an investigation has been made in this project with a view to rectify the defect and improve the breaking strength of straps. The results of investigation reveal that the blooming of the strap is caused by the insoluble phenolic antioxidant which is a component of the protective system that has been added in excess quantity, into the rubber. Further it has also been found that about a 15% reduction in the amount of phenolic antioxidant added and inclusion of 0.15 pphr of zinc - di-ethyl dithiocarbamate completely prevent the bloom, and impart desirable aging resistance to the rubber..