The potential of tannins as thermal co-stabilizer additive for polyvinyl chloride

Abstract

The current study describes the efficiency of tannins, a flavonoid-type natural polyphenolic compound, and its synergistic effect with commercial-type thermal stabilizer into polyvinyl chloride (PVC). Thermal stabilization of PVC has been assessed in an oxidizing atmosphere by rheometric studies and thermogravimetric analysis (TG). In addition, the effect of this phenolic compound on the dynamic mechanical thermal properties has been quantified with the use of dynamic mechanical thermal analysis (DMTA). Also the polymer surface morphology has been estimated by scanning electron microscopy technique. The main degradation stage of PVC samples in TG curves is slightly increased with increasing the tannin compositions in the polymer system. DMTA measurements were done to investigate the tannin effects on the viscoelastic properties of PVC. Before the glass transition temperature, g, of PVC, the DMTA curves show that the values of storage modulus and tan delta of PVC with and without tannins are very similar. In a sequence, after the glass temperature of PVC samples, the DMTA curves confirmed that the PVC samples with tannins have relatively longer flowing stage occurred at lower temperatures by (15–17) °C, as well as lower g by about (4–7) °C per that of PVC sample free from tannins. Global results of TG (DTG) and DMTA show that the thermal stability and thermal flexibility of PVC are slightly increased with the incorporation of tannins.