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Free Radical Mechanism
The relative stability of radicals can be correlated to the hydrogen bond dissociation energies of the parent compound.
High energy free radicals tend to abstract H from the backbone leading to grafting, branching reactions or decomposition for PP.
Lower energy radicals are more stable and selective. They will preferably react on monomers containing double bonds and they are very good "monomer chasers" (acrylics, final stage in EPS, etc.)
| Compound |
Dissociation
Energy (KJ/mol) |
Type of radicals |
 |
381 |
Low energy radicals:
- high selectivity
- good diffusion |
 |
397 |
 |
410 |
 |
435 |
High energy radicals:
- poor selectivity
- good H abstractors
- good diffusion |
 |
439 |
 |
469 |
 |
469 |
 |
498 |
 |
377 |
The above shows the dissociation energies of various hydrogenated compounds.
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