Reinforcement of elastomers by particulate fillers

The reinforcement of elastomers by particulate fillers has been extensively studied in the past, particularly in the 1960s and 1970s. The first reason is naturally the drastic changes in mechanical properties that induce fillers reinforcement Many of the usual applications of elastomers could not be envisaged without the use of particulate fillers. The other reason seems to us to be of a very different nature, and probably resides in the mystery of the reinforcement mechanism that has fascinated many scientists and remains, despite their efforts, mainly not understood today. 

It is necessary to define precisely what is reinforcement, because this word covers very different meanings when applied to thermoplastics, thermosets, or elastomers. Confusion is mainly due to the fact that reinforcement qualifies an increase in mechanical properties, but what is expected as mechanical properties is very different considering the different matrices and applications. 

For plastics, reinforcement results in an increase in modulus and hardness. The effect of particulate fillers is quite clear— they replace a part of the matrix. So modulus becomes higher, but deformation at break decreases in the same time. 

The situation is very different for elastomers the use of reinforcing fillers induces a simultaneous increase modulus and deformation at break. Curiously, the replacement of a part of the deformable matrix by solid objects doesn t reduce its deformability. The increase of these two antagonistic properties characterizes elastomer reinforcement. This fascinating paradox, despite not being fully understood, explains the ability of reinforced elastomers to provide 

The Science and Technology of Rubber. http //dx.doLor l0.1016/B978-0-12-394584-6.00008-X 

---

G. Kraus, Reinforcement of elastomers by particulate fillers, Eirich FR edn., Science and Technology of Rubber. Academic Press, New York, 1978. 

Reinforcement of elastomers by particulate fillers is pursued in order to improve, by an order of magnitude, static and dynamic moduli as well as ultimate properties such as tensile strength and elongation at break. The simultaneous improvement of modulus and elongation is known as the paradox of elastomers . 

Medalia, A. I. Kraus, G., Reinforcement of Elastomers by Particulate Fillers. 

It is clear that ab will be extremely large for inclusions of small radius r, even if the level of adhesion, represented by Ga, is relatively small, only of the order of magnitude of van der Waals attractions. For example, when E is assumed to be 2 MPa, representative of soft elastomers, and Ga is given the relatively low value of 10 J/m, then the critical applied stress for detachment is predicted to reach a magnitude similar to E when the radius of the inclusion is reduced to about 20 ixm, even if the initially debonded zone is as large as feasible, 6 — 45°. These considerations appear to account for some features of reinforcement of elastomers by particulate fillers Fillers (140). 

A. I. Medalia and G. Kraus, in J. E. Mark, B. Erman, and F. R. Eirich, eds.. Reinforcement of Elastomers by Particulate Fillers in Science and Technology of Rubber, Academic Press, Inc., San Diego, Calif, 1994. 

Medalia A, Kxauss G (1994) Reinforcement of elastomers by particulate fillers. In Mark JE, Eiman B, Erich FR (eds) Science and technology of rubber, 2nd edn. Academic, San Diego, CA, pp 387 18... 

Donnet J and Custodero E (2005) Reinforcement of Elastomers by Particulate Fillers, in Science and Technology of Rubber, 3rd ed. (Eds. Mark J E and Erman B) Elsevier, Amsterdam, pp. 367-400. 

---