Cure kinetics of modified lignosulfonate/epoxy blends

Highlights: • Epoxidized and cyclocarbonated lignosulfonates (ELS and CLS) were synthesized. • ELS/DGEBA and CLS/DGEBA blends were cured. • Curing kinetics were studied by dynamic DSC and isoconversional method. • Kamal parameters were calculated by the Sbirrazzuoli and traditional fitting methods. -- Abstract: Epoxidized lignosulfonate (ELS) and cyclocarbonated lignosulfonate (CLS) were synthesized using modifying lignosulfonate. Through FTIR normalization procedure and titration method, the yield of epoxidation and carbonation were determined. Subsequently, two kinds of epoxy blends via the addition of ELS and CLS (20 wt%) as reactive fillers to a conventional DGEBA epoxy resin and curing by diaminodiphenylmethane (DDM) were prepared. The curing process was investigated by non-isothermal differential scanning calorimetry (DSC). For ELS/DGEBA and CLS/DGEBA blends and DGEBA epoxy resin, the curing kinetic parameters of Kamal model were computed via conventional fitting method using experimental reaction rate data. Also, through an approach proposed by Sbirrazzuoli, using activation energy data computed by an advanced integral isoconversional method developed by Vyazovkin, all samples exhibited a similar activation energy dependency on the extent of the reaction which can be attributed to a similar curing reaction mechanism for ELS/ DGEBA blend, CLS/ DGEBA blend and DGEBA.