Study of Chemical Degradation of Cellulose in Cotton Tire Cords as a Result of Road Service and Wheel Testing Carried to Failure

In order to determine whether, and to what extent, chemical degradation occurs in the cellulose of cotton tire cords &dquo;in service,&dquo; cuprammonium fluidity measurements have been made on cords taken from 7.50 -20 tires operated to failure on the Normoyle, Texas, road course, and on a National Bureau of Standards &dquo;wheel.&dquo; For comparison, the fluidity was also determined on cords taken from control tires which were identical in construction. In one test, measurements were also made upon the cotton before processing. Special techniques were required to remove adhering rubber particles from the cuprammonium dispersions before measurements. The results showed that the chemical degradation caused by operation to failure was, in general, of a minor degree-in some cases, even undetectable after long operation. Degradation increased with the increase in percent of normal load on the tires during road operation. Tires operated on the &dquo;wheel&dquo; showed considerably greater degradation than those operated on the road course. Appreciable degradation of the cellulose occurred during the manufacture of the tires, presumably during drying, calendering, and vulcanization. While there were differences in gage of cord used in the tires and differences in climatic conditions dur-