RADIAL TYRE

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. 

A third basic type, T950, has been developed especially for the rubber industry and is intended as a bracing in radial tyres. Arenka 900 and Arenka 930 have physical properties similar to those of Kevlar 29 and 49 respectively. 

As compared to natural rubber, epoxidized grades of natural rubber show improved reinforcement with silica without any coupling agent. Radial tyre tread prepared using formulations based on natural rubber with epoxide... 

Fig. 1. Various articles in which rubber is bonded to metal or other materials (a) bridge bearing (b) cylindrical bearings (c) conical bearing (d) spherical segment bearing (e) cross section of radial tyre...

The production of tyres is among the most important of Automotive applications of adhesion. A modern steel-belted radial tyre contains several reinforcing materials, such as polyester and steel cords. The adhesion of the rubber compound to these cords is of critical importance for the performance and safety of the tyre. Other aspects of Rubber to metal bonding - applications are treated in other articles (see Rubber to metal bonding - basic techniques) here, the adhesion of rubber to the steel cords is discussed. 

The synthetic rubber industry has never looked back and by the 1960s had overtaken NR in terms of production and usage (Table 4.1). At one stage, it was predicted that SBR could eventually replace NR as an industrial elastomer, in particular in tyre manufacturing. However, that prediction never materialized because NR is still needed to provide the required sturdiness and heat resistance in tyre performance. Radial tyres are typically made up of nearly 50% NR whereas aviation tyres require 100% NR in their formulations. Now NR and synthetic rubber complement each other in many applications, each with its niche properties. In the present drive towards sustainable development, NR is viewed as a renewable raw material and is gradually regaining its dominant role. 

NR usage in modern radial tyres has substantially increased. The amount of NR used is about 21 kg per tyre for a radial construction compared with about 9 kg in a bias truck tyre. Bernard and coworkers have compared the NR levels of heavy-duty radial truck tyres to those of the equivalent bias tyre and noted the following increase " ... 

Applications.—Reviews on the applications of polyesters in diverse fields have appeared with weathering performance of reinforced polyesters in building, water-soluble polyester resins with a polyfunctional aromatic acid base, poly(ester-ether) block copolymers - a new type of thermoplastic elastomer, improved polyester radial tyre yam with potential material, pollution, and energy saving,and a thermoplastic polyester review. ... 

Steel cord has been the main reinforcing material for tyres, hoses and conveyor belts for many decades, indeed the first steel reinforced tyres appeared over ninety years ago. However, it was not until the emergence of radial tyres that steel cord became a common form of reinforcement and understandably the adhesion between brass-coated steel cord and rubber compound became a significant factor governing the performance and durability of car and truck tyres. Therefore, it is necessary to achieve a high level of adhesion and sustain this level throughout the service history of the tyre. 

Fig. 17. Rolling resistance ratings of steel radial tyres retreaded with various...

The apparent changes are small and tyres are still round and black with a hole in the middle—but a whole new technology has gone into the design, formulation and performance of the radial tyre as compared with the cross-ply. Machinery which was perfected for the high-volume cross-ply tyre production is not necessarily best for radial tyre making. 

Comments are reported from companies involved in the aircraft tyre industry, which aim to reassure the user about the safety of such tyres following the recent Air France Concorde crash which resulted from tyre debris puncturing the plane s fuel tank. Test and inspection methods used, the use of retreaded tyres, and the trend towards the use of radial tyres are discussed. 

Modern Tire Dealer 70, No.7, June 1989,p.28/35 UNDERSTANDING AND CORRECTING IRREGULAR WEAR ON RADIAL TYRES... 

Some criteria are presented for evaluating the various tyre design theories that are based on the equilibrium shape of the sidewall and on the rolling contour of a tyre. Tyre failure types and the mathematical models by which they can be predicted by modem theories of mbber/cord fatigue are also described. A tyre design theory based on stress-strain optimisation of its elements is proposed as is a hierarchic system of complicated tyre models for calculation of stress-strain cycles. Influence of the cross-section geometry and of the iimer stmcture of the tyre on stress-strain cycles in the belt and bead of radial tyres is investigated. 21 refs. 

Poly(p-phenylene terephthalamide) fibres currently have three major applications, namely as reinforcement in radial tyres and mechanical rubber goods, in ballistic protective fabrics and ropes, and as reinforcement in polymer (particularly epoxy) composites for aircraft and aerospace components. 

The rubber industry is still adjusting itself to the worldwide acceptance of the radial tyre. This came much later in North America than in Europe and the repercussions of the advent of tyres of much greater longevity in this major rubber market has had an important influence on overall rubber usage. The different requirements of the radial tyre vis-d-vis the cross-ply have simultaneously increased the demand for natural rubber relative to SBR. 

In contrast to the natural material the prospects for SBR are less satisfactory. The worldwide acceptance of the radial tyre has cut down... 

Typical formulations and representative properties for heat resistant inner tube compounds intended for use in bias-ply and radial-ply truck tyres are shown in Tables 20 and 21. Crosslinked butyl is included in the radial tyre tube to provide green strength. Butyl reclaim could be used instead, for the same purpose. 

The major usage is in tyres, especially in critical compounds where its uniformity, quality and good flow properties allow the tyre constructors to meet the high standards demanded of steel-reinforced radial tyres. Engineering components such as springs and mountings form another major usage where its unique properties of low creep and compression set resistance are exploited. 

Radial tyres (trucks, automobiles) Strength, stiffness, low fatigue, adhesion, low density, oxidation resistance... 

A typical formulation for a radial tyre tmck tread is shown in Table 35. For improving heat resistance, the use of Perkalink 900 is recommended (289). The recommended loading for this cure system is 0.5 phr. 

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