Reaction-induced phase separation in an epoxy/low molecular weight solvent system

Abstract

Blends based on a stoichiometric mixture of diglycidyl ether of bisphenol A (DGEBA) and 2,2′-bis(4-amino-cyclohexyl)methane (ACHM) and cyclohexane as low molecular weight solvent were studied. The polymerization kinetics data experimentally obtained at different temperatures (30-60°C) were accurate fitted using a mechanistic model. The effect of the solvent over the polymerization rate was analyzed. No influence of the presence of the solvent was found up to 20 wt% of cyclohexane in the sample. The thermodynamic analysis using Flory-Huggins model allowed determination of the initial miscibility of binary blends containing DGEBA/cyclohexane and pseudo-binary mixtures of DGEBA/ACHM/cyclohexane. The presence of ACHM increases the DGEBA/cyclohexane initial solubility. The reaction-induced phase separation was described using a conversion-composition transformation phase diagram. It indicates that phase separation takes place by a nucleation and growth (NG) mechanism. The appropriate selection of composition of the blend and polymerization conditions led to final materials with a desired closed cell porous morphology.