States of water absorbed in water-borne urethane/epoxy coatings

The water absorption properties of water-borne urethane/epoxy coatings are studied using differential scanning calorimetry (DSC) and attenuated total reflectance Fourier transform IR spectroscopy (ATR FTIR) to estimate the methods of interaction between the water and coating. DSC and ATR FTIR are used to categorize water into states based unique and easily identifiable differences in DSC and ATR FTIR measurements. DSC states (Strong, Weak 1, Weak 2, and Free) and ATR FITR states (S0, S1, and S2) appear to correspond to the relative strength of the interaction and the degree of hydrogen bonding between the water and the polymer network, respectively. The dynamics and relative population of each state are estimated with the most populous states being Strong and S1 in urethane, and Strong and S2 in epoxy. Finally six active functional groups within the coating appear to form strong hydrogen bonds with water, and one functional group appears to form weak dipole bonds.

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