Molecular dynamics of a catalysed epoxy resin (DGEBA) as a function of temperature

Epoxy resin polymers primarily consist of long chain hydrocarbons in a network, which exist in an
amorphous structure. These chains undergo relaxations at different temperatures, partly due to the change
in free volume and partly due to the change in kinetic energy. These relaxations necessarily cause a change
in the structure: notably at the glass transition temperature (Tg), where alpha-relaxation processes
dominate and the epoxy changes from a hard, brittle“glassy” form to a viscous, rubbery state. While existing
macroscopic measurements provide an overview of these process they do not address the underlying
physical mechanisms, and a microscopic probe allows observation of these process at a molecular level.
We have observed a change in the Muon response at temperatures that align with alpha, beta and gamma
relaxation regimes across a broad temperature range (50 K to 425 K) as well as changes in both the
diamagnetic and Muonium fractions in T20 and longitudinal field (T1) scans. We have determined estimates
for the Tg at several B fields and calculated activation energies from Arrhenius plots of ln (T1) vs 1 /T and
seen evidence for the gamma and beta relaxations (and determined a preliminary value for the gamma
activation enrgy). These are in good agreement with values obtained from macroscopic measurements,
However, in each case more data is necessary to reduce errors.