Kinetic Model for Gelation in the Diepoxide−Cyclic Anhydride Copolymerization Initiated by Tertiary Amines

Abstract

The best models available in the literature to analyze gelation in the diepoxide-cyclic anhydride copolymerization are based on the mean-field approach. A kinetic model was developed to account for the nonrandom steps of the copolymerization. Two kinetic schemes were employed with one including chain transfer steps. Predicted gel-point conversions as a function of the initiator concentration were compared with experimental results obtained for a system based on diglycidyl ether of bisphenol A, methyltetrahydrophthalic anhydride, and benzyldimethylamine, as initiator. Both kinetic schemes explained the observed first-order kinetics for monomer consumption, after an induction period. However, experimental gel-point conversions could only be fitted by assuming the presence of a chain transfer step regenerating an active species.

Epoxy/anhydride thermosets modified with end-capped star polymers with poly(ethyleneimine) cores of different molecular weight and poly(ε–caprolactone) arms

“…The conversion at the gelation point ( gel is only little affected by the addition of both star polymers, and in all cases the obtained values are within the range commonly observed for epoxy-anhydride systems, around 0.3-0.5 [24,30,31]. This scattering of values can be explained not only by the differences and accuracy of the measuring techniques but from the presence of protic impurities or the occurrence of initiator regeneration reactions that tend to increase ( gel [30][31][32]. Figure 6 shows the thermogravimetric curves for neat and PEI250 formulations.…”

Phase separation induced by a chain polymerization: Polysulfone-modified epoxy/anhydride systems

“…sions using a first-order regression of kinetic curves. 1 Within the experimental error, the gel During the induction period, the initiator I (tertiary amine) is activated through: 1 conversion was practically independent of the PSu concentration.…”

“…Intramolecular The reaction heat for samples with i 0 /e 0 ¢ 0.03 was (DH) max Å 53 kJ/eq, independently of the cyclization was discarded as an explanation for such an effect. 1 So, a uniform polymerization proPSu content. This means that the presence of the thermoplastic did not affect the maximum convercess was considered without including the possibility of formation of microgel particles derived sion attained in the polymerization, within the experimental error of the calorimetric determinafrom intramolecular cyclization.…”

“…p Å 1 0 (DH) res /(DH) max (1) EXPERIMENTAL where (DH) max is the maximum reaction heat obtained from a DSC scan of an unreacted sample. Materials…”

“…Several engineering thermoplastics associmodel for these systems has been recently proated with different thermosetting polymers have posed. 1 Based on this model, a thermodynamic debeen investigated. But, for the most part, high-T g scription of phase separation in thermoplastic-modepoxy systems based on di-, tri-, or tetrafunctional ified epoxies cured with anhydrides, will be develepoxides, cured with aromatic diamines, have oped to explain the morphologies generated and the been selected due to their extended use in addynamic mechanical properties of the resulting mavanced composites.…”