INTERFACIAL CHEMISTRY AND MECHANICAL EFFECTS OF A MULTIFUNCTIONAL PROCESSING ADDITIVE ON CARBON-BLACK FILLED RUBBER

The interfacial effects of a multifunctional additive (MFA), the n-tal low-propane-1,3-diamine salt of carboxylic acid, on carbon black fille d rubber have been studied. The surfaces of three normal-cure-rate car bon blacks, of differing nitrogen BET surface areas, were characterise d by X-ray photoelectron spectroscopy (XPS) and vapour-phase chemical derivatisation and found to contain very few functional groups. The MF A has been found to decompose at ca. 120-degrees-C and the decompositi on to generate diamine and a carboxylic acid species. Bound rubber, de termined by o-xylene extraction, was found to decrease with the additi on of MFA and a limiting bound rubber value was obtained at the MFA lo ading that corresponds to a monolayer coverage of the carbon black sur face. The reduction of bound rubber with the addition of MFA is attrib uted to the release of rubber, immobilised within carbon black agglome rates, as a result of improved dispersion. The mechanical properties o f the rubber were also found to improve with the addition of MFA and a gain this was attributed to the dispersing effect of the MFA on the ca rbon black. Optimum mechanical properties were observed at an MFA load ing which approximately corresponds to a monolayer coverage of the car bon black surface.