TESPT and HTNR can be used as interfacial modifiers for silica –filled rubber compounds, because they provide
better cure characteristic, tensile properties and lesser Payne effect than non-treated compound. However, TESPT is
more effective than HTNR because it imposes better properties than HTNR. For HTNR-treated samples, cure
characteristics, tensile properties, and Payne effect are affected by initial mixing temperature. Scorch and cure times
increase with increasing initial mixing temperature in contrast to cure rate index and torque difference.
Reinforcement index and tensile strength slightly decrease with increasing initial mixing temperature possibly due to
degradation of rubber molecules caused by heat. The Payne effect increases with increasing initial mixing
temperature because low viscosity of rubber results in less effective transfer of the shear stress through the rubber
matrix to breakdown silica agglomerates. For HTNR-treated compound to obtain optimum properties, mixing
should be carried out at initial mixing temperature of 300
C, mixing time of 12 minutes, and rotor speed of 60 rpm.