The Influence of the Acid–Base Balance of the Surface of Silica Filler Particles on the Structure and Properties of Composites Based on Nitrile Butadiene Rubber

The acid–base balance of the surface of silica filler (SF) particles of different grades was determined, and its influence on the structure and properties of mixes based on nitrile butadiene rubber (NBR) was investigated. A near-linear correlation was found between the proneness of the SF particles to flocculate and the concentration of acid centres (ACs) on their surface, in the absence of any pronounced influence on this index of the degree of dispersion of the filler particles. Of all the SF grades investigated, the greatest capacity to form flocculation structures is exhibited by a filler characterised by a higher SF concentration. Increase in the SF concentration leads to an increase in the relative content of physical and covalent bonds in binary mixes of NBR and SF. It is shown that, to reduce the negative effects associated with the formation of flocculation structures, including in the induction period of vulcanisation, it is necessary to select a filler with a lower concentration of these centres.