Oxidation of HDPE in the Presence of PVC Grafted with Natural Polyphenols (Tannins) as Antioxidant

In the current research study, an attempt is made to modification of polyvinyl chloride (PVC) by grafting with biologically based phenolic resin, namely, tannins. The reaction was carried out at 110°C in DMF solution. FTIR spectra show the presence of phenolic hydroxylic groups and other functional groups of tannins into the PVC-tannins derivative. Evaluation of the new PVC derivative as polymeric antioxidant for high density polyethylene (HDPE) was the main purpose of this study. Samples of HDPE containing (0.0, 0.5 and 2.0) %W/W from PVC-tannins and pure HDPE were exposed to thermal program by differential scanning calorimetry (DSC) by temperature sweep from 100°C to 350°C. DSC scans of the thermal oxidation process of pure HDPE as well as HDPE with PVC derivative show oxidation exothermic stage started at 195°C and continues to 285°C. The samples of polyethylene contain the PVC-tannins show more resistance to oxidation reactions until 215°C for HDPE sample stabilized with 0.5% and 221°C for HDPE stabilized with 2.0%. Faster initiation of degradation rate was observed when HDPE contained PVC-tannins. According to the DSC analysis, the PVC derivative can participate in stabilization mechanism of HDPE but at limited performance.