Infrared and birefringence measurements are used to characterize the orient
ational behavior of silica-filled styrene-butadiene copolymers. The orienta
tional data are correlated with the results of equilibrium swelling measure
ments. On the other hand, the role played by a silane couling agent bis(3-t
riethoxysilylpropyl)tetrasulfide (TESPT), or "Si69") on rubber/silica syste
m is discussed. (C) 2001 John Wiley & Sons, Inc.