The effect of type and amount of spin finish on the adhesion of polyester tire cord to rubber

Spin finishes play a critical role in the adhesion and stiffness of polyester (PET) cords in tire applications. This study examined the effects of finish type and amount. Two finishes were compared: neat oil (Finish A) and an oil-in-water emulsion (Finish B). Their influence on adhesion performance and the bending stiffness of PET cords was evaluated. The wettability of PET fibers treated with different finishes and concentrations was studied using the first dip activation solutions. The activation dip is essential to bond resorcinol-formaldehyde-latex (RFL) dip to the inert PET fibers. Therefore, it is crucial to understand how the finish affects the interaction between polyester fibers and the activation dip. The effect of finish type and amount was characterized through H-adhesion, strip adhesion, overcure adhesion, and stiffness measurements. SEM, EDX, and AFM analyses supported these results. PET fibers with emulsion-based finishes were wetted more effectively by the activation dip than those with neat finishes. Cords treated with emulsion-based finishes also showed more consistent adhesion performance, regardless of finish quantity. Overall, optimal adhesion was achieved when the finish on yarn (FOY) was minimized during yarn production.