The effect of steric hindrance on physical properties in an amine‐cured epoxy

A pair of aliphatic amines were synthesized in order to study the effect steric hindrance has on the physical properties of an amine‐cured epoxy resin. The hindered amine (TMSiDA) has NH 2 groups that are obstructed by the presence of adjacent methyl groups while the unhindered amine (SiDA) does not contain any NH 2 steric hindrance. DGEBA cured with TMSiDA is less dense, absorbs less moisture, and has a higher T g than does SiDA/DGEBA. Torsional pendulum results show that TMSiDA/DGEBA has a slightly higher rubbery modulus and a secondary transition at a lower temperature than DGEBA cured with SiDA. Activation energies for the secondary transition were determined for TMSiDA/DGEBA and SiDA/DGEBA and are 19 and 14 kcal/mol, respectively.