Rubber Adhesion of Brass-Plated Steel Tire Cords: Fundamental Study of the Effects of Compound Formulation Variations on Adhesive Properties

Abstract The rubber adhesion of brass-plated steel tire cord has been studied with emphasis on the effects on unaged and aged adhesion of compound formulation variations. A series of 16 test compounds was formulated in which the levels of sulfur, accelerator, stearic acid, zinc oxide and cobalt salt were varied. Adhesion data for two steel cord constructions—4 × 0.25 and 7 × 4 × 0.175 + 0.15—obtained under various unaged and aged conditions are presented. Despite the relatively minor compound differences, a wide variation of adhesion characteristics was observed. Good adhesion following overcure, humidity aging and steam aging was obtained with compounds containing high sulfur levels and high sulfur to accelerator ratios. The adhesion data do not correlate with compound crosslink densities or other physical properties. Rates of brass sulfidization do not correlate with adhesion data either. This was studied in model systems with squalene replacing the natural rubber. Analysis by high-resolution Auger elec...