Filled elastomers

Abstract

Elastomers, particularly those that cannot undergo strain-induced crystallization, are generally compounded with a reinforcing filler. The two most important examples are the addition of carbon black to natural rubber and to some synthetic elastomers (Boonstra, 1979; Rigbi, 1980; Donnet and Custodero, 2005), and silica to polysiloxane ("silicone") rubbers (Warrick et al., 1979). The advantages obtained include improved abrasion resistance, tear strength, and tensile strength. Disadvantages include increases in hysteresis (and thus heat buildup) and compression set (permanent deformation). The mechanism of the reinforcement obtained is only poorly understood in molecular terms. The network chains certainly adsorb strongly onto the particle surfaces, which would of course give an increase in the effective degree of cross linking. This is only part of the effect, however (Mullins and Tobin, 1965; Meier, 1974), but most additional molecular models seem to be highly speculative. Some elucidation might be obtained by incorporating the fillers in a more carefully controlled manner, particularly using sol–gel technology (Erman and Mark, 1997; Mark et al., 2004, 2005a, b, c). We describe several such approaches, along with the incorporation of elastomeric domains in ceramic-like materials, in the remainder of this chapter.