The effect of pendant alkyl chain length on the barrier properties of epoxy/amine crosslinked networks

Aliphatic amido amine crosslinkers have been commercially used in epoxy coatings to enhance water barrier properties for corrosion prevention. However, there is only an empirical understanding of how these aliphatic polyamine crosslinkers affect properties of thermoset polymers, which limits our ability to design newer and more environmentally friendly coating systems. In this work, a series of model aliphatic amido amine curing agents are synthesized and used to create model epoxy/amine networks found in commercial coating formulations. These model systems are interrogated to understand the effects of pendant alkyl chain length material properties including modulus, glass transition temperature, solubility, diffusivity, and permeability of water. This work shows that increasing the pendant aliphatic chain reduces the solubility of water while simultaneously increasing the diffusivity to water in the polymer network.