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 (currently under writing).
The folders are organized by polymer type. In general semi-detailed, reduced, and skeletal 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 single semi-detailed mechanism accounts for the pure polymer degradation.
- Poly(vinyl chloride) (PVC): the proposed mechanism accounts for the pure polymer degradation.
- Currently underway are models for PA, PMMA, and PU and condensed-phase interactions
For most mechanisms, some validation pictures are reported as well.
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 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.
