The effects of natural polyphenols and calcium-based thermal stabilizer on the rheological and thermal resistance behaviors of PVC

With the aim to understand the effect of bio-polyphenols and calcium-based thermal stabilizer on the rheological and thermal degradation properties of polyvinyl chloride (PVC), this paper practically investigates the rheological and thermal degradation behaviors of PVC using melt rheology method. Thermal degradation study was carried out by monitoring the complex viscosity of PVC using a parallel-plate rheometer run by time sweep mode at 215 °C. The presence of calcium into tannin structure after modification allows the later to have HCl scavenger ability which is considered as an essential property of most PVC thermal stabilizers. The thermal stability monitoring by time sweep rheology measurements was further corroborated by dynamic rheological data, indicating that the increase in loading value of tannin–calcium into PVC from 1 to 3 part per hundred of PVC resin resulted in a notable enhancement of the PVC storage modulus and complex viscosity due to the increased thermal stability, stable chemical structure and a higher level of polymeric chain entanglements. The rheological parameters obtained by frequency sweep at 165 °C in terms of storage and loss moduli and damping factor proved simultaneously that the PVC formulations with tannin–calcium exhibit an obvious improvement in the rheological properties which were comparable to that of PVC stabilized with Reapak B-NT/7060, an industrial-type thermal stabilizer. The results obtained indicated a promising correlation between the thermal stabilization performance of tannin–calcium as a new and fully bio-based thermal stabilizer and the rheological properties of PVC.