Surface Preparation of Rubbers

Almost all types of elastomers can be bonded to a large variety of substrates by the process known as vulcanization. The strength of similar bonds by adhesive bonding, or post-vulcanization (PV) bonding, as it is also called, was originally believed to be much weaker and less resistant to environmental exposure. Published work has demonstrated that this is not true, with some exceptions. The advantages of PV bonding are  

Solvent washing and abrading are common surface treatment methods for most elastomers, but chemical treatment is often applied for maximum strength and other properties. Many synthetic and natural rubbers (NRs) require cyclizing with concentrated sulfuric acid until hairline cracks appear on the surface. Some rubbers require primers for optimum bonding. 

Research has shown that the bondability of elastomers is a function of polarity. The less polar EPDM and butyl elastomers, the more difficult they are to bond than are the more polar nitrile, neoprene, styrene-butadiene rubber (SBR), and NR. 

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Abstract This chapter constitutes one of the very few reviews in the existing literature on shoe bonding, and it gives an updated overview of the upper to sole bonding by means of adhesives. The surface preparation of rubber soles and both the formulations of polyurethane and polychloroprene adhesives are described in more detail. The preparation of adhesive joints and adhesion tests are also revised. Finally, the most recent development and technology in shoe bonding is described. 

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