Rubber Stocks for Improved Performance of Polyester Cord Tires

Abstract

Abstract Carcass stocks were developed with acceptable properties and good adhesion to polyester tire cords after severe heat aging in laboratory tests. These stocks contained vulcanization accelerators that did not liberate amines and were based either on synthetic poly (isoprene) (IR)/butadiene/styrene (SBR) elastomer blends, as recommended in previous work, or natural rubber/SBR compounds containing an additive to inhibit the deleterious effects of amines present as impurities in NR. Standard SBR/poly (butadiene) (BR) tread stocks containing amine-free accelerators were developed to match the exceptionally long scorch time and good physical properties attained with sulfenamide accelerators normally used in such stocks. Large batches (˜400 pounds) of amine-free tread stock were processed without any scorch problems on a commercial Banbury mixer and tread extruder. With these tread stocks, containing amine-free accelerators, it is possible to build completely amine-free polyester cord tires. In a variety of wheel tests designed to assess durability under extreme conditions, 2-ply tires with cords of Dacron polyester containing amine-free tread and carcass stocks showed highly improved durability (180-440 per cent) compared to control tires made with stocks containing amines. In a wheel test simulating the running of a tire underinflated for an extended period (low pressure endurance test), tire durability increased with decreasing amine content of the rubber stocks used. In a special high temperature tire fatigue test to produce break-above-bead failures, tires combining an experimental Dacron polyester with low carboxyl content and in amine-free stocks ran 350 per cent longer than tires of standard T-68 Dacron in amine containing stocks. These tests clearly illustrated the additive benefits of combining an improved polyester with stocks having reduced amine content.