Dr. S. Coppola

Elastomer Research Center, Versalis SpA, Ravenna/Ferrara, Italy

Nonlinear Viscoelasticity and energy dissipation of filled rubber for tyre application: effect of chain-end functionalization



The tire compound is usually composed of two or three polymers and a number of other materials like fillers, plasticizers, oil, vulcanization accelerators, sulphur. Nevertheless, the nature of the pure polymer(s) in terms of Molar Mass Distribution (MMD) and architecture can still have significant effects on the dynamic-mechanical properties of cured compounds that are crucial for the tire performance (in particular, grip, fatigue, and Rolling Resistance).
As far as molecular architecture is concerned, it has been already shown in the literature that SBRs (Styrene-Butadiene Rubbers i.e. random copolymer of styrene and butadiene) synthesized by anionic polymerization in batch reactors are good candidates for low Rolling Resistance (RR) compared to SBRs synthesized in continuous reactors. Such difference of RR is mainly due to narrower molecular weight distribution and the absence of low molecular-weight fractions responsible for energy dissipation in the cured compound.
Nevertheless, as widely described in the literature, chain-end functionalization is an effective alternative to reduce energy dissipation (and doing so, RR) without affecting processability during rubber compounding (mixing) and following “shaping” operations (calendaring, extruding, molding).
In this work, we attempted to answer the following questions:
1.      does chain-end functionalization improve filler dispersion?
2.      does chain-end functionalization reduce energy dissipation of cured compounds?
3.      Is the chain-end functionalization effect always positive? Does it depend on polymer molar mass/architecture?
In order to find the necessary information to answer these questions we characterized uncured and cured compounds by small and large amplitude oscillatory shear as well as by tensile testing.

Some conclusions have been drawn regarding the two big families of tyre rubber compounds: silica filled rubber compounds and carbon black filled rubber compounds.

Date: 15/1/2016
Time:16:00 (coffee & cookies will be served at 00:00)
Place:FORTH Seminar Room 1