FILLER-ELASTOMER INTERACTIONS .10. THE EFFECT OF FILLER-ELASTOMER ANDFILLER-FILLER INTERACTION ON RUBBER REINFORCEMENT

In comparison to carbon blacks, the lower dispersive component, gamma( s)d, and higher specific component, gamma(s)sp, of surface energy of s ilicas lead to weaker polymer-filler interaction and strong filler net working. This results in higher compound viscosity, higher alpha(F), h igher modulus at low strain, lower bound rubber content, and lower mod ulus at high deformations. After silanization of the silica surface wi th the bifunctional silane bis(3-triethoxy-silylpropyl)tetrasulfane (T ESPT), the tendency for filler networking is decreased due to a drasti c reduction in gamma(s)sp, whereas polymer-filler interaction is great ly strengthened by the introduction of covalent bonds between the fill er surface and the rubber chains. As a consequence, most rubber proper ties are improved, such as compound processability, modulus at high el ongation, and dynamic vulcanizate properties, Although silica modifica tion with the monofunctional hexadecyltrimethoxy silane (HDTMS) has a similar effect as modification with a bifunctional silane in reducing filler networking, the lack of polymer-filler interaction leads to low modulus at high strain and poor failure properties.