Effect on the Antioxidant Capacity of Polypropylene by Vanillin: A Natural Antioxidant Extracted from Cotton Stalk Lignin

Vanillin (VA) was extracted from cotton stalk lignin by UV photocatalysis method using CoSUP2+/SUP/NiSUP2+/SUP as a catalyst, the yield of which was quantitative analyzed through gas chromatography-mass spectrometer and high performance liquid chromatography. The structure and thermal properties were compared between extracted and standard VA, which showed basically consistent. PP/VA materials characterized by fourier transform infrared spectroscopy were prepared by melt intercalation and subjected to 20 days thermal oxygen aging. Thermal gravimetric analysis and oxidation induction time results showed VA (0.9 wt%) could improve the thermal stability of polypropylene (PP) by 33.4 ℃ and 49.03%. Differential scanning calorimetry confirmed that VA increased the crystallinity of PP reaching to 15.70%. After 20 days aging, mechanical test showed the impact strength and breaking elongation retention of PV-3 (0.9 wt%) were 10.0% and 14.8% higher than those of PP; surface scanning electron microscopy showed that PV-3 had the most smooth surface.