Natural rubber truck tread

The tread must have the best possible grip to the road. Grip is inversely related to elasticity, and natural rubber has good elasticity but poor grip, so no natural rubber is used in automobile tire treads. Treads are blended of SBR and polybutadiene in an approximate ratio of 3 1. Truck tire treads do have natural rubber, between 65-100%, to avoid heat buildup and because grip is not so necessary in heavy trucks. Aircraft tires consist of 100% natural rubber. 

A balanced combination of properties is the criterion of performance. In tread-wear resistance, cold butadienerstyrene tires are approximately 20-30 per cent superior to natural-rubber or hot rubber treads. However, in tire carcass or sidewalls, natural rubber exhibits superior performance, especially in truck tires, because of lowfeV heat build-up. 

The increase in natural rubber usage translates into approximately 21kg per tire for a radial construction compared with approximately 9 kg found in a bias truck tire. Natural rubber compounds also tend to find use in covers of high-performance conveyor belts where a similar set of performance parameters such as those of a truck tire tread compound are found. Low hysteretic properties, high tensile strength, and good abrasion resistance are required for both products. 

Polybutadiene/natural rubber blends tend to find application in truck tire tread compounds and side valls. Polybutadiene is also blended vith SBR in treads. Here blend ratios tend to be optimized for factors such as vear resistance, traction requirements, rolling resistance, and damage resistance. Empirical guidelines for determining blend ratios are based on the vork of Nordsiek and co vorkers revie ved earlier [4]. Briefiy... 

Other patents include Ternary Blend of Polyisoprene, Epoxidized Natural Rubber and Chlorosulfonated Polyethylene to Goodyear Tire Rubber, U.S. Patent 5,736,593, April 7, 1998, and Truck Tire With Cap/Base Construction Tread to Goodyear Tire Rubber, U.S. Patent... 

Volumewise, natural rubber represents about half of all the rubber used in producing tires today. Typically, natural rubber is used as a blend with either SBR or BR in tire rubber compounds. NR/SBR compound blends are used in the tire carcass coat, cushion gum, earth-mover retreads, light truck treads, bead filler, chaffer rim flange, and motorcycle treads. NR/BR compound blends are commonly used to make passenger tire treads, sidewalls, high-performance treads, camelback, and heavy-duty truck treads. 

The primary application for halobutyl rubber is in tires. The combination of low gas and moisture permeability, high heat and flex resistance, and ability to covulcanize with highly chemically unsaturated rubber has secured the use of these rubbers in the innerliners of tubeless tires. Passenger tires use chlorobutyl alone or in a blend with 20 to 40% natural rubber. High-service steel-belted truck tires use 100% bromobutyl innerliner compoimds. Chlorobutyl is also used for truck inner tubes for its superior heat resistance compared to butyl rubber. Halobutyl rubbers are added to sidewall compounds for improved ozone and flex resistance, and to certain tread compounds for improved wet skid resistance and traction. 

Tire treads for cars, inferior to natural rubber with respect to heat buildup and resilience, thus not used for truck tires belting molded goods, gum, flooring, rubber shoe soles, electrical insulation, hoses About 70-60% used for iimer tubes for tires... 

A natural rubber rich undertread layer can enhance the adhesion between belt or cap-ply and tread whilst a thicker subtread compound may be included to offer some additional benefits of low hysteresis for car tyres and low heat generation for truck tyres within the bulk of a thick section. The cure system needs better flexibility and low heat generation. Typically the cure system will be based on CV/SEV. A general composition for a tyre tread base is depicted in Table 41. 

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