R ational design of reinforced rubber

Filled elastomer systems have been studied extensively over the past several decades, especially in the application to tire performance. During this time, many attempts have been made to explain reinforcement of an elastomer when fillers are added. These reinforced properties include enhanced strength, modulus, abrasion resistance, and dynamic mechanical properties. Several approaches have been used to separate the contributing influences and to explain how they work. The majority of these approaches look at the structure and property relationships of the fillers and rubbers independently and as a synergistic combination. These approaches have evolved into the following major areas: filler structure, hydrodynamic reinforcement, and interactions involving fillers and elastomers. This paper will review the major works in each of these areas and attempt to offer an overall view of reinforcement of elastomers. Special attention will be paid to the relationships between filler structure and how it may be used to predict reinforcement properties. The general topics that will be covered included filler structure and characterization, rubber and filler interactions, mechanical reinforcement /hydrodynamic effect, and a fractal approach to explaining reinforcement.  2002 Elsevier Science Ltd. All rights reserved. 1 . Introduction ratios of additives and measure the effects. Recently however, efforts have been directed at understanding the Passenger car tires are composed of many different mechanistic role of fillers in order to predict their effect on materials, e.g. steel belt, nylon fibers, gas barrier layers, to reinforcement. form an overall product. This paper will focus on reinforcement of elastomers that are used in tire treads and side walls, emphasizing carbon and silica elastomer com2 . Filler morphology and characterization pounds. The elastomers are solution and emulsion styrene– butadiene rubber, natural rubber, and blends. Additives are Studying the morphology and structure of fillers requires used to increase the rubber’s strength, wear resistance, several techniques that probe a broad size scale (nm–mm) performance and processing. These additives consist of and describe different structural features. Fillers are made fillers like carbon black and silica, curatives to promote up of primary particles at the smallest size-scale, Angstrom cross-linking, mixing aids such as aromatic oil to aid the to micron, which are strongly bonded to other primary dispersion of fillers, and anti-degradants such as antiparticles to form an aggregated structure. The aggregates oxidants and anti-ozonents. Already it can be seen that range from the nanometer to micron size-range and these combining all of these materials together results in a can interact with other aggregates through weaker seccomplex composite with end properties depending on the ondary bonding to form agglomerates. Tables 1 and 2 formulation used. The processing of these materials also show the methods commonly used to determine filler affects the end properties. morphology and how the morphologies relate to filler The resulting properties desired for filled rubbers inproperties. These methods give information about the filler clude good mechanical properties, both static and dynamic, primary particle size, surface area, surface structure and and tire specific properties such as traction, wear resistenergy aggregate size / structure, and agglomerate size / ance, and rolling resistance. Typically these properties are structure. This section will focus on 2 categories of filler obtained through a series of experiments that vary the characteristics: structure and surface area. 2 .1. Structure *Corresponding author. Tel.: 11-513-556-3096; fax: 11-513-556-