Natural rubber inner liner

Hot asphalt applications had been used for many years in concrete tanks, inner lined with brick for similar service, and also, of course, unlined wood tanks made from timber, and small pickling tanks made by hollowing out cavities in granite blocks. But the use of hot asphalt as a liner for steel tanks had been unsatisfactory due to the erratic cold flow of the asphalt which demonstrated selective adhesion to steel and so would tear and open cracks in the membrane system in the areas of cold flow below the points where it adhered. To overcome this difficulty, a number of inventive persons experimented with the manufacture of asphalt sheet lining materials, similar in form to the sheets of natural rubber, in which the asphalt was compounded with various admixtures, including rubber. These asphaltic compound sheets were then warmed sufficiently to make... 

BR is used in nearly all parts of the tire with the exception of the inner liner it is always blended with natural rubber (NR) or styrene-butadiene rubber (SBR). Apart from the extrudability, in NR blends the Nd-BR polymers exhibit advantages in all important compound and vulcanizate properties. Also, in SBR blends Nd-BR leads to the best vulcanizate properties in comparison with all other types of BR. 

Barrier Materials. Polymers are often used as barriers to keep small molecules in or to keep them out. One common example is rubber tubes for tires or more recently the inner liner of tubeless tires. The purpose of such a material is to contain air under pressure to maintain tire inflation. From the data in Table I, it is clear that butyl rubber is a much better material for this purpose than natural rubber. Because of this, butyl rubber has entirely displaced natural rubber from this market. Aside from its prohibitive price, silicone rubber would be totally unsatisfactory for this use because of its high gas permeability. 

The most outstanding property of butyl rubber is its very low air permeability, which has led to its extensive use in tire inner tubes and liners. A major disadvantage is its lack of compatibility with SBR, polybutadiene, and natural rubber. An ozoneresistant copolymer of isobutylene and cyclopentadiene has also been marketed. 

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 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). 

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