Self-Vulcanisation

The anti-abrasive or anti-corrosive rubber linings are applied to the metal surface by adopting different kinds of bonding systems such as ebonite bonding, chemical adhesive bonding or self-vulcanising cement bonding. 

In the self-vulcanising cement bonding method, precured soft rubber sheet is bonded to the metal by a cement which cures at ambient temperature thereby effecting the required bond strength between the soft rubber and the metal. This technique is known as the cold bonding technique. 

In more recent years, lining compounds have been developed that vulcanise at ambient temperatures. Most polymers can be used for such compounds, although most materials are based on natural rubber, acrylonitrile-butadiene rubber and polychloroprene. These compounds contain accelerators which usually give rise to a material which has a delay in the onset of vulcanisation with a subsequent rapid rise in cross-link formation to give full vulcanisation in 6 to 8 weeks. Such materials, unless to be used within a few days of manufacture, are refrigerated to arrest the self-vulcanisation. 

When continuous sampies are required, particularly from rapidly varying or sensitive soils, a Delft sampler may be used (Fig. 7.6). This can obtain a continuous sample from ground level to depths of about 20 m. The core is retained in a self-vulcanising sleeve as the sampler is continuously advanced into the soil. 

The most important limitation of polyisobutene is its tendency to cold flow because of which it cannot be used in self-supporting forms. This defect can be overcome by copolymerisation with isoprene and vulcanisation of product with sulphur. The product is called butyl rubber. This product was first marketed in 1943 in USA. 

Raman and IR spectroscopic studies dealing with the qualitative and/or quantitative determination of rubber compounding ingredients, i.e., the elastomer itself [22, 26-31], fillers [32, 33], vulcanisation chemicals and other additives [34-37], are not included here. The same applies to studies dealing with the crosslinking of elastomers by means of chemicals other than sulfur or peroxide [38-41], self-crosslinking of elastomers blends [42-44], crystallisation (strain-induced) [45-48] and oxidation/ageing [49-53]. 

The bonding is achieved by different methods. The hard component can contain undercuts where the rubber is anchored during its vulcanisation, a primer on the hard component or even using self-adhesive silicone rubber will give sufficient anchorage. 

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