Kinetics Study of PVA Polymer by Model-Free and Model-Fitting Methods Using TGA

Area of Science:

• Polymer Science
• Materials Science
• Chemical Kinetics

Background:

• Polyvinyl alcohol (PVA) is a versatile polymer used in fibers, films, and membranes.
• Understanding PVA's thermal degradation is crucial for optimizing its processing and applications.
• Thermogravimetric Analysis (TGA) is a key technique for studying polymer thermal behavior.

Purpose of the Study:

• To determine the kinetic parameters of Polyvinyl alcohol (PVA) thermal degradation.
• To compare the effectiveness of six model-free kinetic methods.
• To identify the most appropriate reaction mechanism for PVA pyrolysis.

Main Methods:

• Thermogravimetric Analysis (TGA) was performed at heating rates of 20, 30, and 40 K min^-1.
• Six model-free methods (FR, FWO, KAS, STK, K, VY) were used to calculate activation energy (E).
• Model-fitting using Coats-Redfern (CR) and Criado's master plot identified the reaction mechanism.

Main Results:

• TGA revealed two degradation stages for PVA, with the first stage (550-750 K) analyzed for kinetics.
• Activation energy (E) values ranged from 104 kJ mol^-1 (VY) to 199 kJ mol^-1 (FR) for the conversion range (0.1-0.7).
• The Coats-Redfern method yielded an average activation energy of 126 kJ mol^-1, and a second-order reaction (F2) was identified as the best mechanism.

Conclusions:

• The thermal degradation of PVA is best described by a second-order reaction mechanism.
• Kinetic analysis using multiple methods provides a comprehensive understanding of PVA's thermal decomposition.
• The study determined thermodynamic parameters (ΔH, ΔG, ΔS), indicating an endothermic reaction process.