Multistage Thermal Decomposition Kinetics of Glycidyl Azide Polymer-Based Thermoplastic Elastomers: A Constrained...

Area of Science:

• Polymer Chemistry
• Materials Science
• Chemical Engineering

Background:

• Glycidyl azide polymer (GAP)-based polyurethane is an energetic thermoplastic elastomer (ETPE) vital for advanced solid propellants.
• Its complex thermal decomposition, involving overlapping reactions, hinders accurate kinetic modeling and limits engineering applications.

Purpose of the Study:

• To develop a novel kinetic analysis method for accurately characterizing the thermal decomposition of GAP-based ETPEs.
• To resolve overlapping decomposition reactions and determine precise kinetic parameters for improved material design.

Main Methods:

• A constrained asymmetric Gaussian deconvolution strategy was applied to derivative thermogravimetric data of GAP-based ETPEs (50 wt% GAP) at multiple heating rates.
• Cross-validation using Friedman and Flynn-Wall-Ozawa methods determined apparent activation energies without assuming reaction mechanisms.
• Generalized master plots and the Šesták-Berggren model were used for mechanistic insight and kinetic equation development.

Main Results:

• The complex decomposition was successfully resolved into five distinct stages (azide cleavage, backbone scission, carbamate cleavage, hydrocarbon degradation, residue decomposition) with high goodness of fit (R² > 0.998).
• Apparent activation energies were determined for each stage, revealing significant differences.
• The Šesták-Berggren model excellently fitted three major stages (R² > 0.996), indicating synergistic nucleation-growth and phase boundary mechanisms.

Conclusions:

• The developed constrained deconvolution method provides a robust approach for analyzing complex thermal decomposition in GAP-based ETPEs.
• Accurate kinetic parameters were obtained, enabling the development of high-precision kinetic equations for these energetic materials.
• The methodology is applicable to various ETPE formulations and other complex energetic polymer systems.