Investigation on effects of dynamic fatigue frequency, temperature and number of cycles on the adhesion of rubber to steel cord by a new testing technique

The effects of dynamic fatigue frequency, temperature and number of cycles on the adhesion of rubber to steel cord in a carcass recipe were examined. A new test method with special rubber/steel cord specimens was developed for the dynamic fatigue measurements which were carried out on a De Mattia Rubber Flexometer. It was found that the dynamic “pull-out forces” decreased with increase of fatigue frequency, but first increased and then decreased with increasing temperature and the number of fatigue cycles. The adhesion failure mainly occurred in the rubber phase rather than at the rubber/steel cord interface. The covered rubber on the “pulled-out” cord after fatigue appeared to form a screw thread and the greater pull-out force corresponded to more uniform and clearer screw threads in the rubber remaining on the cord. Steel cord with an outer wrapping wire had greater static adhesion force and better adhesion after fatigue; the adhesion failure mainly occurred in the rubber phase but some occurred at the contact point of the outer wrapping wire and the wrapped main steel wires. The screw threads of rubber coverage appeared along the twist direction of the outer wrapping wire. SEM indicated that un-dispersed filler agglomerates may initiate adhesion failure.