Rubber blends: kinetic numerical model by rheometer experimental characterization

A robust kinetic numerical model for natural rubber NR–poly-butadiene PB blends vulcanized with sulfur is presented. For a preliminary experimental insight used then as benchmark, a 70% NR with 30% high-cis PB blend vulcanized in presence of sulfur and two accelerants (TBSS and DPG) in different concentrations is tested under standard vulcanization conditions (rheometer) at three different vulcanization temperatures, namely 150, 170 and 180 °C. The numerical model reproduces normalized experimental rheometer curves using a Han’s kinetic model for NR and a modification of the Han’s model proposed recently by the authors for PB. The model bases therefore on existing kinetic approaches that proved to be effective for NR and PB separately, but merging them linearly to cope with NR–PB peculiar reactions occurring in a blend. Han’s model depends on three rate constants, whereas the approach used for PB is characterized by four kinetic parameters. The linear interaction between PB and NR (with amount of rubber involved not a priori known) is again assumed ruled by a Han’s model. The mathematical approach proposed is therefore characterized by 10 rate constants plus an additional parameter represented by NR–PB concentration involved by the interaction. Such constants are estimated by standard best fitting against experimental data. Quite good match is found, showing that the procedure may be useful for practical purposes in all those cases where expensive experimental investigations are not possible.