Crosslinking of mixtures of DGEBA with 1,6‐dioxaspiro[4,4]nonan‐2,7‐dione initiated by tertiary amines. I. Study of the reaction and kinetic analysis

Abstract

ABSTRACT:The anionic copolymerization of a Diglycidyl ether of bisphenol A (DGEBA) epoxy resin and a bislactone has been studied with different initiators. The kinetics of the process has been dealt with in detail, and it has been detected the existence of different competing curing mechanisms: a quasi-alternating copolymerization between the epoxy monomer and the bislactone, and homopolymerization of the epoxy resin. In presence of an excess of DGEBA, the copolymerization first takes place, and then the excess of epoxy monomer can homopolymerize. The bislactone induces an apparent accelerating effect because it reduces the extent of epoxy homopolymerization and therefore the termination reactions associated with it, thus allowing a complete cure with a reduced amount of initiator.

Crosslinking of mixtures of diglycidylether of bisphenol‐A with 1,6‐dioxaspiro[4.4] nonan‐2,7‐dione initiated by tertiary amines: III. Effect of hydroxyl groups on network formation

“… a Gelation was determined using oscillatory rheometry or TMA (where indicated). The activation energies obtained from the gel times ( E gel ) for DGEBA with a molecular weight of 381 g mol −1 are compared with the activation energies calculated from dynamic DSC data ( E α, int ) presented elsewhere16 using similar formulations but with DGEBA with a molecular weight of 364 g mol −1 and cured with 2 phr (or 5 phr, as indicated) 1MI. …”

“…The conversion of the epoxy groups was determined from the exotherm by assuming a reaction heat of 100 kJ mol −1 ,21, 29 and assuming that the lactone ring‐opening enthalpy was negligible 3, 16. The error in the heat of polymerization was estimated as ± 5%.…”

“…Tertiary amines have been reported to be effective anionic initiators for the curing of not only epoxides,12–22 but also of lactone‐,23, 24 bislactone‐15, 16 or carbonate‐modified25–27 epoxy formulations. In the case of mixtures of bislactone with a stoichiometric excess of epoxy groups, it has been found16 that an alternating copolymerization between the epoxide and the bislactone takes place from the beginning of the curing process and that only when the epoxy–bislactone copolymerization has consumed all of the bislactone do the remaining epoxide groups homopolymerize. Current unpublished work shows that the presence of hydroxyl groups significantly affects the curing kinetics of epoxide–bislactone mixtures using tertiary amine initiators.…”

Control of reactions and network structures of epoxy thermosets

“…Other cyclic comonomers can be copolymerized with epoxies according to an anionic alternating copolymerization mechanism and are used in epoxy thermoset technology. They include bicyclic and spirocyclic bis(γ-lactone)s [57][58][59][60][61][62]. These are comonomers dedicated to the development of shrinkage-free or expanding curing formulations.…”

Simultaneous Measurement of Effective Chemical Shrinkage and Modulus Evolutions During Polymerization

“…The corresponding partial exotherm can be defined as ΔH(t). Then, the curing extent, p(t), at time t can be simply determined as [54][55][56][57][58][59] …”