The effects of varying the polymer composition on the cut growth characteristics of E/P/1,4 HD tire treads



Experimental ethylene–propylene–1,4-hexadiene polymers covering a range of compositions which possess satisfactory processing characteristics and economics have been evaluated in passenger car tires with emphasis on groove cracking. The tearing energy criterion was used in a laboratory test to correctly predict the groove cracking behavior of the tires made from these polymers. Road tests indicate that ethylene–propylene–1,4-hexadiene tripolymers containing 36%–42% propylene and 1.8%–2.2% diene exhibit resistance to cut growth and abrasion which is superior to standard SBR–BR bias tires. Polymers containing more than 42% propylene or 2.2% diene were inferior in wear and resistance to groove cracking, but sufficient data are not available to pinpoint the reason.