Condensed-phase polymer degradation kinetic Mechanisms. Evaluation of gas-phase pyrolytic and gasification reactivity are underway at CRECK modelling POLIMI.
The present repository is the polymer pyrolysis subset of the comprehensive one on GitHub of Creck Modeling Lab. The mechanisms reported here are those employed and validated for my PhD Thesis.
The folders are organized by polymer type. In general semi-detailed, reduced, and multistep mechanisms are available. Specifically:
- Polyethylene (PE): different models are available for HDPE and LDPE according to the degree of detail involved in products and radicals description. For HDPE both semi-detailed, reduced and multistep versions are availble. The same holds for LDPE with the semi-detailed, reduced and multistep mechanisms are reported. Thermodynamics and transport have been assessed as well.
- Polypropylene (PP): has a semi-detailed, reduced and multistep mechanism available as well. Thermodynamics and transport have been validated. The mechanism for APP has not been reported due to the lower importance of APP in general wastes.
- Polystyrene (PS): the proposed mechanisms account for all structural differences. The semi-detailed mechanism and both a reduced and multistep version are currently available with validated thermodynamic properties.
- Poly(ethylene terephthalate) (PET): a semi-detailed and a multistep are proposed, accounting for the pure polymer degradation. Both models consider a single pseudo-phase that represents both polymer and char residue.
- Poly(vinyl chloride) (PVC): the proposed semi-detailed mechanism accounts for the pure polymer degradation.
- Currently underway are models for PA, PMMA, and PU and condensed-phase interactions
The folders of each polymer investigated report all the literature experimental data employed for validation purposes. For most mechanisms, some validation comparisons are reported as well. I do not own any of these data, they are generally taken with plot_digitizer from the of plots of published papers (so there is lots of rumor which hinders the quality of DTG comparisons).
In each polymer folder there is a subfolder labelled "Exp_data". This is composed of subfolders labelled with the corresponding operating condition (e.g., 10 Kmin) and containing a json file (Exp_data.json) with all the data inside. The data are structured by type (TG, DTG, DSC, Gas_Yield), author, and values (with units). No DOI is reported herein, but you can find all the exact references on the mechanism papers. Gas yields data are already lumped to the models' species.
Each Exp_data folder also hosts a file "Operating_conditions.json", which reports the information used for model simulation (e.g., how the temperature profiles are estimated, and so on).
Experimental data on mixture pyrolysis and volatiles molar yields have not been yet placed here.
The aim of the proposed kinetic models is to reproduce the main features of the degradation process at low computational cost. This refers to describing the characteristic degradation times (mass-loss profiles), product distribution, and heat requirements.
The kinetic mechanism are of the semi-detailed or lumped kind employing a functional group approach:
- Long polymer chains are described with functional groups characteristic of the polymer moieties (mid- and end-chain groups) recognized by the "P-" in their name
- Short chains, i.e. compounds of interest, are described with real species as C2H4, C15H30, etc
Thermochemistry has been succesfully validated for PE, PP, and PS. Transport parameters are evaluated with a simplified approach based on critical temperatures and pressures, see Holley et al. (2009). The present models cannot be directly coupled to the creck gas-phase mechanism, but further work is underway to assess the secondary gas-phase reactivity.
