CHAPTER 19. Mechanical Properties of Natural Rubber Composites Filled with Macro- and Nanofillers

Abstract

Generally fillers incorporated in rubber composites can be divided into two categories, reinforcing and non-reinforcing fillers. The reinforcing fillers play a significant role in increasing or at least maintaining the strength of rubber composites, while the non-reinforcing fillers are added to reduce cost. The filler reinforcement in rubber composites depends on particle size, the structure of filler particles, and surface activity. As particle size decreases (from micro to nano), the surface area increases, providing more available contact between the rubber molecule and the filler particle. The high structure filler exhibits a high number of primary particles per aggregate, which is called strong aggregation, whereas low structure fillers show only weak aggregation. These aggregates may form loose agglomerates linked by van der Waals interactions. Fillers that have chemically active surfaces from various chemical groups provide good interaction between rubber and filler through the formation of strong covalent bonding. The hydrophobic and hydrophilic nature of rubber and filler also influence the compatibility and dispersibility of a filler in the rubber matrix. Basically, the addition of reinforcing fillers will improve mechanical properties but reduce the elasticity of rubber composites. The reinforcement of rubber with nanoparticle fillers combines the elastic behaviour of rubber with the strength and stiffness of the reinforcing phase.