Abstract:
A novel method for simulating the torque and temperature curves from a torque rheometer thermal stability test
on poly(vinyl chloride) (PVC) was developed. A mathematical model was proposed which combines the chemical
kinetics involved in the thermal degradation and stabilisation process of PVC with heat transfer and viscosity
relationships within the torque rheometer. The model coefficients were fitted to data obtained from previous
experiments with a program written in the Python programming language using the Levenberg-Marquardt
Algorithm (LMA) with multiple starts. The mathematical model fits the torque rheometer data successfully
depending on the characteristics of the torque curve. The model fit is successful when the torque curve follows
the expected behaviour. An unsuccessful model fit occurs when the torque curve deviates from the expected
shape in a very specific way. In the degradation phase the torque curve increases to a local maximum, decreases
to a local minimum and then increases again. The exact reason for the dip in torque is unknown.
