Kinetic analysis of HPP-UMMFE composites: Unveiling thermal stability and degradation mechanisms using Thermogravimetric analysis

Abstract

The scholarly examination delves into Kinetic Analysis of Polypropylene Homopolymer (HPP) when augmented with Unmodified Minor Mineral Fuller’s Earth (UMMFE). UMMFE, HPP, and HPP composites were analyzed for their functional groups using FTIR. FTIR spectra of the FE-filled composites indicated a slight weakening, evident from the broadening of the absorption peak at 1376 cm^-1, which is characteristic of polypropylene. Additionally, a peak at 1020 cm^-1, corresponding to the Al-Si-O bond of clay, was also observed in the HPP composites. The various intricacies governing HPP degradation by loading of UMMFE were meticulously analyzed with the help of Thermogravimetric analysis (TGA) using single heating rate of 10°C/min and contrasted with those of unreinforced HPP employing congruent processing conditions to underscore the pivotal role played by UMMFE. The kinetic parameters were calculated using two methods: Coats–Redfern (CR), Broido’s (BR) method respectively. The activation energy values for HPP in first phase of degradation ranged from 104 to 286 kJ/mol in the conversion range of 0.2 to 0.9. Interestingly, the apparent activation energy from CR method in second phase of degradation universally in context to prepared compositions were observed to decrease in conversion range from 0.2 to 0.5, indicating a reduction in endothermic reactions. Conversely as observed in general from 0.6 to 0.9 degree of conversion, activation energy increased, suggesting occurrence of exothermic reactions during pyrolysis. Similarly, the activation energy values were calculated using BR which exhibited behavior analogous to that observed with CR Method. Despite obtaining similar trends in activation energy by both methods, the results were also revalidated by calculating standard deviation which fetched a result of 0.04 kJ/mol for first phase and 7.21 kJ/mol for second phase of degradation. The study revealed potential of the prepared composite for sustainable bio-fuel production, designing pyrolysis reactors and facilitate recycling after end-of-life from the products processed thereof.