Dynamically Determined High-Pressure Compressibilities of Three Epoxy Resin Systems

Abstract

Three Epon 828 epoxy systems which had significant variation in glass transition temperatures were tested dynamically in plate impact experiments to obtain their pressure‐volume response. The choice of hardener determines the transition temperature of the system through the degree of crosslinking and structural changes. For this study, the hardeners used were metaphenylenediamine, Z and D. The dynamic ``equilibrium'' compression curves for the three systems are identical within experimental uncertainty and are adequately represented by the Z system shock‐velocity‐particle‐velocity results of U=2.64+1.66u(mm/μsec); ρ₀=1.194 g/cm³. The dynamic results may be reduced to isothermal conditions through the use of the Gruneisen equation and appropriate thermodynamic quantities. These dynamic isotherms are compared to static compressibilities obtained by other investigations using piston apparatus. While the static results show marked variation of compressibility with processing conditions, this was not confirmed by the dynamic results. Possible reasons for this discrepancy are advanced.