Isothermal Cure of Bisphenol Epoxy Resin with a Nonlinear Aliphatic Polyamine Hardener

Abstract

An amine terminated polypropylenimine dendrimer (DABdendri-(NH 2 ) 4 ), was employed as a new nonlinear aliphatic curing agent for diglycidyl ether of bisphenol A (DGEBA). Isothermal curing reaction kinetics of DGEBA/DAB was investigated with a differential scanning calorimeter (DSC). The autocatalytic model proposed by Kamal was demonstrated for simulating the reaction kinetic in the initial stage of the cure. It was found that the overall reaction order, m þ n, was in the range 2.3688-2.5980. The rate constants of k l and k 2 , showed a good Arrhenius fit to temperature and the associated activation energies was estimated to be 60.41 kJ/mol and 55.66 kJ/mol, which showed in agreement with values reported for common epoxy-amine systems. In the latter stage of curing, diffusion control was considered and a diffusion factor was incorporated into the autocatalytic model; therefore, it was possible to accurately predict the cure kinetics over the whole range of conversion.

Molecular Mobility in Hyperbranched Polymers and Their Interaction with an Epoxy Matrix

“…More generally, the reaction kinetics of bisphenol-A epoxy resins cured with polyamido-amine dendrimers has been studied [11,12], and it has been reported that, in comparison with the use of EDA as curing agent, the curing kinetics using polyester-amine dendrimers is very different, presenting two stages of cure and less heat of reaction [13]. The use of polypropylene-imine dendrimers as curing agents in epoxy systems is quite widely reported [14,15,16], and it appears that the molecular architecture of the dendrimers, in particular their steric hindrance and the number of attached –OH groups [14], greatly affects the reaction kinetics. It is clear that suitable dendrimers can effectively crosslink epoxy resins, and this may be advantageous if the dendrimers exhibit improved compatibility with epoxy resins over the conventional linear aliphatic amine curing agents of low molecular weights.…”