Crosslinking Process Analysis of Polyisoprene and MQ Copolymers Blends by the Rheological Method

Abstract

Crosslinking process kinetic parameters of mixtures based on low-molecular polyisoprene and MQ‑copolymers have been investigated by means of rotational rheometry. The rheological method allows tracking of the changes in the principal parameters of the system, such as viscosity, dynamic moduli, and the mechanical loss tangent during the entire chemical curing process. The evolution of viscous and viscoelastic properties of the system have been recorded under isothermal conditions as well as under conditions of continuous increase in temperature. Duration of the gelation in the systems has been determined under conditions of shear deformation via extrapolation of the dependence of reciprocal viscosity on time as well as from the crossover of the loss factor in a wide frequency range. Rheological properties of the filled systems about the gelation transition have revealed the power dependence of the dynamic moduli on the frequency, the critical parameter being equal to 0.54 at 100°C. The increase in the fraction of the inorganic component in the MQ-copolymers from 1 : 2 to 1 : 4 has led to an increase in the gelation time.