The objective of this work is to study the thermal degradation kinetic parameters of polypropylene (PP) and compare them to those of a polypropylene/starch blend (PP/S) (70/30 (wt %)), taking into account the effect of photodegradation caused by natural weathering. Samples were taken from tree shelters exposed to four years of natural weathering and compared to the unexposed material stored under laboratory conditions. Nonisothermal (dynamic) thermogravimetery was used with five different heating rates (β): 5, 10, 15, 20, and 25 °C min-1. Several analytical model-free methods were used to determine the kinetic parameters, including the Friedman, Coats and Redfern, Kissinger, and Flynn-Wall- Ozawa (FWO) methods. The model-fitting method of Criado was also applied to determine the optimal mechanism of degradation that the polymers followed. In addition, an analytical solution was developed to mathematically model the experimental data and estimate the kinetic parameters. The analytical approach was developed based on each degradation stage of the PP/S blend, considering starch degradation at first, followed by PP. A change in the degradation mechanism could be deduced because of the effect of weathering and starch addition, which affected the kinetic parameters of the degradation reaction. The thermal stability of the materials was also affected, because of the natural weathering and addition of starch, which, on the other hand, affected the kinetic parameters of the degradation reaction.
ASJC Scopus subject areas
- Chemical Engineering(all)
- Industrial and Manufacturing Engineering