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Dynamic mechanical analysis experiments were carried out to investigate the mechanical properties of four types of chemically different epoxy resins. Pressure−volume−temperature (PVT) experiments were performed to determine the free-volume hole fraction (h PVT ) of each epoxy resin using the Simha−Somcynsky lattice−hole theory. Using the Williams− Landel−Ferry equation, the correlations between the relative hole fraction (1 − h PVT T r /h PVT , where h PVT T r is the hole fraction at a reference temperature T r ) and four typical parameters reflecting dynamic mechanical properties [storage modulus (E′), loss modulus (E″), damping factor (tanδ), and complex viscosity (|η*|)] were studied in the temperature range from T g(PVT) (the glass transition temperature determined by PVT data) to T g(PVT) + 100 °C. In the temperature range from T g(E onset ′ ) (temperature corresponding to the intersection of the two tangent fitting lines in the E′(T) curve indicating the glassy-state and glass-transition stages) to T g(PVT) + 100 °C, the variations in the four dynamic mechanical parameters with a relative hole fraction could be separated into two distinct categories: (i) log[E′(T)] and log[|η*|(T)] decreased linearly to their minimum values and then remained nearly unchanged with increasing relative hole fraction, and (ii) log[E″(T)] and log[tanδ(T)] first increased monotonically to their maximum values and then decreased linearly with the increasing relative hole fraction. This study demonstrates that the PVT technique is a feasible and reliable experimental method to determine the hole fractions of thermoset polymers.

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