Hydrocarbon Rubbers with Little or No Unsaturation

3 Hydrocarbon Rubbers with Little or No Unsaturation 1.2.3.1 Ethylene-Propylene Rubbers 

Ethylene-propylene rubbers (EP) have low total surface energies with small polar components. As would be expected, the adhesion of paints and adhesives to untreated EP is poor. To achieve good adhesion to EP, the introduction of suitable functional groups is necessary unless a diffusion mechanism can operate. Bragole [26] found that UV treatment of EPDM coated with a thin layer of benzophenone resulted in large increases in the adhesion of acrylic, epoxy and urethane paints to the polymer. 

Ellul [27] subjected EPDM/polypropylene and natural rubber/polypropylene blends to various halogenation treatments, namely fluorine/carbon dioxide, sodium hypochlorite/ acetic acid and bromine water. With the natural rubber blend, there was a substantial uptake of fluorine, chlorine and bromine in the surface regions as indicated by energy dispersive X-ray analysis and with all three pre-treatments the adhesion to an acrylic tape was greatly enhanced. In contrast, with the EPDM blend, fluorine was the only reagent which reacted with the rubbers and only this treatment resulted in a significant increase in adhesion to the acrylic tape. The above results can be explained in terms of the different concentrations of carbon-carbon double bonds in the two blends. Substantial incorporation of chlorine and bromine could occur with the natural rubber-polypropylene blend but not with the EPDM blend. However, fluorine gas will react readily with saturated hydrocarbons [28,29] and therefore the incorporation of fluorine into the EPDM blend is not surprising. 

Lawson [30] using X-ray photoelectron spectroscopy (XPS) found that trichloroisocyanuric acid (TCICA) in ethyl acetate did not chemically modify EPDM. 

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