VISCOELASTIC PROPERTIES OF N6 AND N66 TIRE CORDS: MORPHOLOGICAL ANALYSIS.

The significance of the mechanical loss of tire cords in tire temperature rise during service is well known. With polymeric fibers such as PET, nylon 6, nylon 66, etc. the mechanical loss is controlled by the viscoelastic responses of the fiber. Among the polymeric materials used as tire reinforcements, nylon 6 and nylon 66 tire cords represent a particularly interesting case, because the tire temperatures extend on both sides of the loss peak observed at approximately 90-100 degree C. Since the tire operating temperatures depend on severity of the driving conditions and ambient conditions, the fraction of the cords operating below the loss peak maximum and above it vary from case to case. But increases in the load on tires and speed always increase the fraction of cords which operate above the loss peak maximum. This trend has an unexpectedly large consequence on the relative performance of nylon 6 and nylon 66 tires, a topic which attracted a great deal of attention during the last few years. The differences between the two tire cords and the advantages of nylon 6 under severe driving conditions have been reported elsewhere. In this article, we review and identify factors causing the differences in the position, intensity and shape of the mechanical loss peak of nylon 6 and nylon 66 tire cords.