Synthesis and characterization of fatty acid modified amines with improved water barrier properties

Fundamental studies aimed at elucidating the key contributions to corrosion performance are needed to make progress toward effective and environmentally compliant corrosion control. Epoxy/amine systems are typically employed as barrier coatings for corrosion control, however, the curing agents used for coating applications can be very complex, making fundamental studies of water and oxygen permeability challenging to carry out. Creating model building blocks for epoxy/amine coatings is the first step in carrying out these studies. This work demonstrates the synthesis and characterization of model amine building blocks from saturated fatty acids and diethylenetriamine (DETA) with tunable hydrophobicity. The glass transition temperature (T_g) of modified amine samples suffered a 45–50 °C T_g reduction, which has been attributed to a loss of labile hydrogens available for crosslinking in these samples. It was observed that the fatty acid modified amines exhibited a reduced diffusivity to water of up to 50%. This has been attributed to the increased tortuosity of samples with a pendant aliphatic chain in the network. Samples with modified amines were observed to have lower solubility of water (S) of up to 30%. We propose that the reduction in S can be caused by a dilution of oxygen in the polymer network due to the addition of aliphatic pendant chains.