TYRE INNER LINER

The permeation rate of fluids (gases and liquids) through rubber is of particular importance in applications where the rubber s function is to contain a fluid, such as a tyre inner liner, fuel and liquid petroleum gas hoses, diaphragms, etc. Permeability is the product of a pressure gradient across a membrane and the diffusivity (the rate at which fluids will enter and leave a polymer) [22]. Solubility determines the amount of fluid held in the polymer. 

Sandstrom and co-workers utilized the cyclized polyisoprene polymers incorporated into tyre tread compounds to improve traction, tread wear and tear resistance. Cyclized polyisoprene is further based upon the discovery that blends of cyclized polyisoprene polymers with halobutyl rubber and/or NR can be employed as tyre inner liner formulations. 

The Bayer Tear Analyser is described, and examples are presented of its use in predicting the cut growth performance of rubber compounds for high performance car tyre treads, car and truck tyre breakers, radial truck tyre treads and truck tyre inner liners. Good correlation between the test results and the service performance of various tyre components is demonstrated. The application of the machine in optimising tyre inner liner formulations based on bromobutyl robber and blends of bromobutyl and butyl rubber is also described. 6 refs. 

Polysar Bromobutyl X2 Esso Bromobutyl 2244 Tyre inner liners, heat... 

Halobutyl rubbers are used in applications requiring butyl rubber behaviour but in which either standard butyl rubber cannot be used, or the halobutyl rubbers offer sufficient technical advantages over regular butyl to compensate for their higher cost. Thus, halobutyl rubbers are used in tubeless tyre inner liners, white sidewall and cover strip stocks, and blends... 

A very low air permeability for a rubber (although not particularly low for polymers in general) which has led to extensive use in tyre inner tubes and liners. 

The main applications of butyl rubber are in wire and cable applications, inner tubes, inner liners in tubeless tyres, tyre curing bladders, and pharmaceutical closures, the latter utilising the low... 

The influence of polymers and additives on the service life of non-tread tyre components is discussed on the basis of results obtained from studies of inner liner, belt and sidewall compounds. The effects of the bromine content of bromobutyl rubbers on the performance of inner hners, and of sulphenamide accelerators on the adhesion of NR belt compounds to brass coated steel cords were investigated. The mechanical properties and ageing and ozone resistance of black sidewall compounds consisting of NR blends with neodymium catalysed polybutadiene protected with different antioxidants and antiozonants were also evaluated. 5 refs. 

Ability to selectively remove different parts of the tyres (i.e., tread, sidewall and butyl-based inner liner). 

Halobutyl rubbers are used in inner liners and sidewalls for tyres, heat resistant inner tubes, tank linings, pharmaceuticals, automobile mounts, and an increasing number of other applications. Annual world consumption doubled between 1974 and 1979, and is expected to exceed 100 X lOH in 1980. 

Bromobutyl rubbers are normally selected when optimum performance is required, for example, in inner liners and inner tubes for heavy-duty and premium quality tyres. Chlorobutyl rubbers are selected when service demands are less severe but exceed the capabilities of non-halogenated butyl rubbers, for example, in covulcanisable blends with natural rubber... 

The functions of the inner liner in a tubeless tyre are to retain air in the tyre, to maintain air pressure at the correct level (which is important in terms of rolling resistance and tyre life) and to prevent air and moisture from penetrating the tyre carcass in amounts sufficient to cause damage to, or loss of cohesion of, the carcass components. 

The properties required of a liner to perform this function include the ability to adhere permanently to the tyre carcass, heat resistance, flexibility and flex crack resistance over the full operating temperature range and a low level of permeability to air and moisture. Regular butyl rubber cannot be used in this application except, in the form of butyl reclaim, as a flexible, highly impermeable filler for other elastomers, because it cannot be made to adhere strongly enough to the tyre carcass. Bromobutyl rubber possesses all the properties, in ample measure, required for premium quality inner liners, but a few parts of natural rubber are normally included in chlorobutyl liner stocks to ensure that they have adequate cured bond strength (see Tables 16 and 17). 

The inner liner forms the vital internal membrane which hold the inflation medium at an elevated pressure within the structure of the tyre. In early days... 

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