Tread wear

Processings and Properties. Polybutadiene is compounded similarly to SBR and vulcanised with sulfur. The high cis-1,4 type crystallizes poorly on stretching so it is not suitable as a "gum" stock but requires carbon black reinforcement. It is generally used for automotive tires in mixtures with SBR and natural mbber. Its low T (—OS " C) makes it an excellent choice for low temperature tire traction, and also leads to a high resilience (better than natural mbber) which ia turn results ia a lower heat build-up. Furthermore, the high i j -polybutadiene also has a high abrasion resistance, a plus for better tire tread wear. 

Perhaps the main reason for the widespread acceptance of polybutadiene rubbers arose when it was found that they gave a vastly reduced tendency for the circumferential cracking at the base of tyre tread grooves with crossply tyres when used in blends with SBR. With crossply tyres now replaced by radial tyres, this factor is no longer of great importance but the rubbers continue to be used because of the improved tread wear and good low-temperatue behaviour imparted by their use. 

Defect limit describes a parameter which we are all familiar with. For example, when you buy original automotive equipment tires there are built-in tread wear indicators. These wear indicators are molded into the bottom... 

The most stringent requirements are good tread wear, low RR, and superior traction. Out of these parameters, if one improves, the other will deteriorate. 

Use of highly dispersible silica together with silanes and high vinyl S-SBR has met all critical magic triangle requirements like good dry and wet traction, reduction in tread wear, and low RR. 

These are unstable forms of elements which decay by the emission of radiation. A radioactive isotope of an element behaves chemically in the same way as the non-radioactive form, but its radiation may be detected and measured by a suitable instrument. In the rubber industry radioactive isotopes are used in beta ray thickness gauges, in studying the precise role of sulphur in vulcanisation, in the speedy determination of tread wear in tyres, etc. See Beta Rays. 

Tread wear during the life of a tyre represents a loss of only 30-40% of the actual tread compound. For worn, undamaged tyres a fresh patterned tread may be fixed to the casing. 

The rubber stock, once compounded and mixed, must be molded or transformed into the form of one of the final parts of the tire. This consists of several parallel processes by which the sheeted rubber and other raw materials, such as cord and fabric, are made into the following basic tire components tire beads, tire treads, tire cords, and the tire belts (fabric). Tire beads are coated wires inserted in the pneumatic tire at the point where the tire meets the wheel rim (on which it is mounted) they ensure a seal between the rim and the tire. The tire treads are the part of the tire that meets the road surface their design and composition depend on the use of the tire. Tire cords are woven synthetic fabrics (rayon, nylon, polyester) impregnated with rubber they are the body of the tire and supply it with most of its strength. Tire belts stabilize the tires and prevent the lateral scrubbing or wiping action that causes tread wear. 

Use Biochemical radioactive tracer studies medical treatment of leukemia, skin lesions, etc. industrial measurements, e.g., tire tread wear, thickness of ink and paint films lead detection. 

Tread wear resistance, abrasion resistance, traction, speed stabihty, protection to casing, rolling resistance, ice skid resistance, durability... 

In the retreading market, new silicas are expected to improve properties of retreaded tires which are currently inferior to new tires.Tread wear resistance and rolling resistance arc substantially lower with retreaded tires. 

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. 

Styrene-butadiene rubber is the largest volume synthetic elastomer commercially available. It ean be produced by free-radical emulsion polymerization of styrene and butadiene either at 50 to 60°C (hot emulsion SBR) or at about 5°C (cold emulsion SBR). The two kinds of SBR have sigmfieantly different properties. The hot emulsion SBR process, which was developed st, leads to a more branehed polymer than the cold emulsion process. Cold SBR has a better abrasion resistance and, eonsequently, provides better tread wear and dynamic properties. 

The bias-belted tire, on the other hand, has much of the tread wear and traction advantage of the radial tire, but the shift from bias to bias-belted tires requires less radical change in vehicle suspension systems and in tire building machines. These features make the bias-belted tire attractive to both automobile and tire manufacturers. 

When considering only solution polymers, polymer microstructure has a greater effect on tire tread compound performance. Table 9.11 illustrates the impact on tire traction, rolling resistance, and tread wear of a polybutadiene tread on which the vinyl-1,2-butadiene level had been increased from 10% to 50% (Brantley and Day, 1986). The corresponding drop in wear and increase in tire rolling resistance are in agreement with the empirical rules presented by Nordsiek (1985), who attributed such tire property trends to the polymer Tg. 

There is improved abrasion resistance associated with a preferential carbon black-BR phase distribution in blends of NR-BR and SBR-BR. The first abrasion studies on the effects of carbon black phase distribution in NR-BR blends were reported by Krakowski and Tinker (1990a,b). Tread wear resistance was found to increase progressively with increasing carbon black in the BR phase, which was determined from TEM analyses. Tse et al. (1998) have shown that blends of dispersed BIMS in BR matrix failure due to fatigue can be retarded if the mean distance between the crosslinks of the BIMS is less than 60 nm. 

Shoulder belt wedge High-adhesive rubber compound in the shoulder region between the belts and casing improves tread wear and durability. 

Rib designs with design elements principally in the circumferential direction are the most common type of tread pattern and show overall good service for all-wheel-position summer service. On heavy tmcks, they are used nearly exclusively on steer and trailer axles because of their lateral traction and uniform wear characteristics. Rib/lug combinations tend to find use on all-season tires, which require a balance of good tread wear, traction, and wet skid. On heavy-duty truck drive axles, where forward traction is a prime requirement and where fast tread wear occurs as a result of torque-induced slip, the highway lug design is required. For off-highway service conditions the tread pattern assumes a... 

Tread wear, which encompasses slow wear rates, fast wear rates, and uniformity of wear. 

Until recently, it was generally understood that only a few percent of ground rubber can be used in new tires. Scrap Tire Management Council reports that 5% of recycled tire rubber is used in an original equipment tire for the Ford Windstar. Although no other information on the amount of devulcanized rubber used in new tires is available in open literature, a possibility exists for the use up to 10 wt.% of recycled tire rubber in new tire compounds (Myhre and MacKillop, 2002). It was reported that actual road tests of buck tire containing 10 wt.% of the devulcanized rubber in the tread exhibited tread wear behavior almost equal to that for standard type with the new rubber compound (Fukumori et al., 2002). The increase in the amount of recycled mbber in tires is growing but it is likely that results will not be available for a number of years. 

PROPERTIES OF SPECIAL INTEREST Standard emulsion SBR is a general purpose rubber. Most widely used synthetic rubber in the world. Better tire tread-wear and aging properties than natural rubber. Good abrasion resistance and crack initiation resistance. Poor in tack and heat build-up. Physical properties are poor without reinforcing fillers. Solution SBR is a speciality rubber and more expensive than emulsion SBR. Solution SBR with high vinyl and styrene levels is used in high performance tire treads to improve wet traction. Also used as impact modifier in plastics and as thermoplastic elastomers. 

Shortly after Word War II, the American synthetic rubber industry began production of cold SBR, from which, it was found, superior tire rubber, especially as regards tread wear, could be prepared. Subsequent studies showed that the reduction in temperature from 50 to 5°C had little or no effect on the microstructure of the polydiene units (cis-1,4 versus trans-1,4 versus 1,2), or on the comonomer composition, but did exert a marked influence on the molecular weight distribution (Table VI). It was also shown [70] that the... 

---