Natural Compounds for the Stabilization and Coloration of Polypropylene
The effects of two new natural substances (celery and Lycium chinense fruits) on the stability of polypropylene (PP) were investigated. Thermogravimetric analysis (TGA) and oxidation induction time (OIT) were conducted to investigate the thermal and thermo-oxidative stability. Melt flow rate (MFR) was tested for the processing stability. Results showed that the addition of natural substances did not change the thermal degradation behavior of PP, but greatly enhanced the thermal and thermo-oxidative stability. The temperature at 5 wt% loss (T5%) of PP-L1.2 sample was 13 °C higher than pure PP. The OIT value of PP-L1.2 sample was about 1.8 times as many as that of pure PP after the first extrusion. Moreover, the change of MFR for PP-L1.2 sample between first and fifth extrusions was smaller than PP. As for PP-C1.2 sample, the T5% and OIT were both increased compared with PP. The change of MFR was also smaller than PP. All results confirm that celery and Lycium chinense fruits can be used as antioxidants and colorants for PP.