Itaconic acid has attracted a lot of interest as a green
and low-cost
building block toward the synthesis of biobased polyesters and polyurethanes
with a wide range of applications in the UV-curing field. However,
the thermal curing of itaconic acid-derived polyesters has been not
extensively investigated. To gain deeper insight into the thermally
induced crosslinking process, the curing of poly(hexylene itaconate)
was investigated by advanced isoconversional analysis performed under
isothermal and non-isothermal conditions. Rheology and thermal analysis
pointed out a three-step mechanism (initiation, propagation, and termination)
typical of free-radical polymerization associated with the double
bond conversion. Moreover, due to the comprehensive information obtained
by different analytical techniques such as isothermal DSC, ATR-FTIR,
and DMTA, we speculate that thermo-oxidative mechanisms occur under
thermal curing conditions of poly(hexylene itaconate). Thus, β-scissions
of poly(hexylene itaconate) chains might lead to the formation of
anhydride and oligomeric radicals, which can recombine to a highly
branched and crosslinked poly(hexylene itaconate) resin.