Role of chemically modified carbon black surfaces in enhancing interfacial adhesion between carbon black and rubber in a composite system

The surface and adsorption characteristics of carbon blacks treated with H3PO4, KOH, and C6H6 were investigated. The equilibrium spreading pressure (pi (e)), surface energy (gamma (s)), and specific surface area (S-BET) were studied by the BET method with N-2 adsorption. In this work, an interpretation based on the nitrogen amount adsorbed for filling a monolayer (a(o)) was proposed for the determination of the Gibbs free energy of nitrogen adsorption, allowing evaluation of the equilibrium spreading pressure or London dispersive component of the surface free energy of the carbon blacks studied. Also, the microstructures of the carbon blacks treated were investigated by transmission electron microscopy. Acidic treatment led to significant decreases in adsorption amount, S-BET, and surface free energy of the carbon blacks, due to aggregation of the microstructures and increasing weight of the swollen specimen in an equilibrium state. Polar basic and nonpolar chemical treatments resulted in an increase of the equilibrium spreading pressure or London dispersive component of surface free energy of the carbon blacks without significantly changing the surface and adsorption properties and microstructures. Results from the surface energetics and parameter of polymer-filler interaction (chi) showed that the tearing energy of the composites is greatly dependent on the carbon blacks studied in the treatment. (C) 2000 Academic Press.