On the Physical Properties of Rayon and Nylon 66 Tire Cords at Elevated Temperature'

Currently produced rayon and nylon tire yarns, greige cords, and dipped cords (the nylon dipped cord having been Kidde treated, hot-stretched, and heat-set) were tested for reversible physical properties at 70°, 100°, 220°, and 300° F. As the temperature was raised, the nylon samples showed greater loss of breaking strength, greater increase in extensibility, greater loss of Hookean slope, and (for the cords) greater increase in con tracting force than the corresponding rayon samples. Heat aging at 220° F. in an air- circulating oven for periods up to five days caused no significant change in the values ob tained at 220° F. for strength, extensibility, or Hookean slope for either the rayon or nylon samples.

The rayon cords had the expected advantage of a high initial modulus; this advantage over the nylon cords was improved as the testing temperature was increased from 70°- 300° F. It is believed that this would mean less growth and a smaller degree of cyclic extension, for tires made from the rayon cords, under temperature conditions likely to be met with in normal driving.