Blooming of Compounding Ingredients in Natural Rubber Compounds under Different Peroxide Loading

Abstract

Rubber compounds normally shows blooming phenomena whereby a thin layer of powdery material or films and oils formed on the surface. These blooms are usually low molecular weight compounding ingredients such as curing agents, accelerator, processing aids and activators that migrated to the surface. Excessive blooming can degrade the vulcanized rubber and reduced its quality. It is therefore necessary to determine the compounding ingredients that bloomed in an effort to reduce the effect of blooming. This study was aimed at identifying the compounding ingredients that dominate the blooming process. Sulphur, paraffin wax and zinc diethyldithiocarbamate (ZDEC) with specific functions were added as compounding ingredients in natural rubber (SMR L). Dicumyl peroxide were added as the curing agent at several loadings. The rubber compounds were cured at 150oC in the presence of dicumyl peroxide as curing agent at several loadings. They were stored under room temperature for blooming to take place. Blooms were analysed using FTIR and EDX. EDX analysis detected the major element present in the blooms to be carbon at 53.5% abundance. Similarly, FTIR results produced high intensity of C-H band at 2916 cm-1 and 722 cm-1 which are due to stretching and bending vibration of C-H paraffinic. It was concluded that paraffin wax preceded sulphur and ZDEC in blooming of SMR L.