Stabilization effect of lignin in polypropylene and recycled polypropylene

The influence of lignin on the oxidative stability of polypropylene (PP) and recycled polypropylene (recPP) plaques has been examined by differential scanning calorimetry under non-isothermal conditions. Lignin was used as a dry powder in the concentration range from 0.5 to 10 wt%. Further, the mixture of lignin with Irganox 1010 was tested. Onset temperatures of oxidation, protection factors and antioxidant effectiveness were evaluated. The results show that lignin exerts a stabilizing effect in both virgin and recycled polypropylene. The protection factor increases with lignin content in the PP matrix. The mixture of lignin with Irganox 1010 exhibits a synergistic influence in the recycled polypropylene. Moreover, the influence of the lignin content on Vicat softening temperature (VST) was determined for the evaluation of polypropylene heat resistance. VST showed that the presence of lignin improves the heat resistance of PP and recPP plaques.