SILICA GRAFTED WITH EPOXIDIZED LIQUID POLYBUTADIENES: EVIDENCE FOR THE MECHANISM OF REINFORCEMENT

Precipitated silica with backbone epoxidized liquid polybutadiene grafted onto its surface has recently been presented as a new reinforcement material that requires significantly less energy to disperse in comparison wtih the traditional in situ silanization process. This potentially provides better traction and hard-handling performance in car tire treads, without greatly increasing rolling resistance. The purpose of this study was to seek evidence proving the previously proposed reinforcement mechanism, through solid-state H-1 low-field nuclear magnetic resonance and equilibrium swelling experiments. The evidence points to an increase in the amount of epoxidized chain segments chemically bonded to the silica surface and to an increase in coating-matrix entanglements with increases in the degree of epoxidation and cure of the coated silica. Such evidence is consistent with the hypothesis of increasing the number of entanglements and/or their progressive loss of mobility with an increase in the degree of epoxidation and decrease in temperature, which is in close agreement with the proposed mechanism.