Kinetic Analysis of Flame Retardant Additive Effects During Polypropylene Pyrolysis

Restricted (Penn State Only)
- Author:
- Caputo, Gianna
- Area of Honors:
- Chemical Engineering
- Degree:
- Bachelor of Science
- Document Type:
- Thesis
- Thesis Supervisors:
- Hilal Ezgi Toraman, Thesis Supervisor
Michael John Janik, Thesis Honors Advisor - Keywords:
- Pyrolysis
Flame Retardants
Plastic Additives
TGA
Polypropylene
Kinetic Analysis - Abstract:
- The purpose of this study was to understand the additive effects of two common flame retardants on the thermal degradation path of polypropylene (PP). The plastic pollution accumulating in the environment is composed of several polymer types and additives, such as flame retardants, that enhance their mechanical properties. Pyrolysis has been proposed as a solution to create a circular plastic economy by converting polymers to their monomer form through thermal degradation. However, interactions between polymers and additives and how they affect outcoming pyrolysis products need to be understood. To start this, the non-isothermal pyrolysis of polypropylene with added TBBPA and melamine was studied using thermogravimetric analysis (TGA) at various heating rates, i.e., 20, 10, and 5 °C/min. Iso-conversional methods such as the Friedman and Flynn-Wall and Ozawa (FWO) methods were applied to evaluate the activation energies of pure PP and mixtures of PP and flame retardant. When combined with TBBPA, PP undergoes a two-stage degradation process, whereas with melamine, it follows a three-stage process, suggesting initial reactions between PP and melamine. Maximum TBBPA degradation occurs at a lower temperature (~313 °C) compared to theoretical modeling (~335 °C), indicating interactions with PP. Melamine degradation aligns with theoretical modeling, but an unexpected initial DTG peak suggests reactions with PP during state changes. However, PP degradation seems unaffected by the combination with flame retardants according to theoretical models. The activation energy of each mixture was calculated to be consistent with PP, averaging at 253.8 and 241.1 kJ/mol with the Friedman and FWO methods. High variation between minimum and maximum activation energy values ranging from 14.2 to 387.1 kJ/mol confirms multistep thermal degradation, indicating that the iso-conversional methods are not suitable for the kinetic evaluation of these mixtures. This prompts future investigation on how the degradation paths could be changing the kinetics of waste PP pyrolysis.