Abstract
This work details a methodology for parameterization of the kinetics and thermodynamics of the thermal decomposition of polymers blended with reactive additives. This methodology employs Thermogravimetric Analysis, Differential Scanning Calorimetry, Microscale Combustion Calorimetry, and inverse numerical modeling of these experiments. Blends of glass-fiber-reinforced polybutylene terephthalate (PBT) with aluminum diethyl phosphinate and melamine polyphosphate were used to demonstrate this methodology. These additives represent a potent solution for imparting flame retardancy to PBT. The resulting lumped-species reaction model consisted of a set of first- and second-order (two-component) reactions that defined the rate of gaseous pyrolyzate production. The heats of reaction, heat capacities of the condensed-phase reactants and products, and heats of combustion of the gaseous products were also determined. The model was shown to reproduce all aforementioned experiments with a high degree of detail. The model also captured changes in the material behavior with changes in the additive concentrations. Second-order reactions between the material constituents were found to be necessary to reproduce these changes successfully. The development of such models is an essential milestone toward the intelligent design of flame retardant materials and solid fuels.
Highlights
The combustion of polymeric materials can be characterized as a coupling between gas-phase and condensed-phase phenomena
An attempt was made to simulate the thermogravimetric analysis (TGA) and DSC data obtained for the polybutylene terephthalate (PBT)/GF/DEPAL blends using a combination of the PBT decomposition model and DEPAL
The reaction parameters of this interaction were initially estimated through a fitting of the TGA and DSC data obtained for PBT/GF25-DEPAL8 and further adjusted by fitting of the data collected for PBT/GF25-DEPAL16
Summary
The combustion of polymeric materials can be characterized as a coupling between gas-phase and condensed-phase phenomena. The condensed-phase phenomena, broadly referred to as pyrolysis, have been less understood due to their inherent complexity and a lack of experimental capabilities for direct monitoring of relevant chemical transformations [1,2]. The kinetics of thermal decomposition is, perhaps, the most important characteristic of the pyrolysis process [3] This kinetics is usually derived from a global measurement, such as thermogravimetric analysis (TGA), which provides information on mass loss from a thermally thin sample exposed to a linear temperature ramp. Polymers 2018, 10, x FOR PEER REVIEW provides information on mass loss from a thermally thin sample exposed to a linear temperature ramp
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