Cure characteristics, crosslink density and degree of filler dispersion of kaolin-filled natural rubber compounds in the presence of alkanolamide

Abstract

The effects of alkanolamide (ALK) addition on cure characteristics, crosslink density and degree of filler dispersion of kaolin-filled natural rubber (NR) compounds were investigated. The kaolin filler was incorporated into NR compounds with a fixed loading, 30.0 phr. The ALK was prepared from Refined Bleached Deodorized Palm Stearin (RBDPS), a waste product of cooking oil production, and diethanolamine. The ALK is an oily material and added into the filled NR compounds as a rubber additive at different loadings, 0.0, 3.0, 5.0 and 7.0. The kaolin-filled NR compounds with and without ALK were vulcanized using a semi-efficient vulcanization system. It was found that ALK decreased the scorch and cure times and improved filler dispersion of the kaolin-filled NR compounds. The higher the ALK loading, the shorter were the scorch and cure times. It was also found that ALK increased the crosslink density of kaolin-filled NR compound up to 5.0 phr of loading. Due to its oily properties, The ALK acted as an internal plasticizer which decreased the minimum torque and improved the degree of kaolin dispersion in NR phases. The higher the ALK loading; the lower the minimum torque and better the filler dispersion.