Application and limitations of current understanding to model failure modes in coatings

Impact of carbamate formation on the surface tension of epoxy‐amine curing systems

“…Carbonate symmetric stretching [80,81,84,96,98,99] 1285 N COO À Carbamate stretching [80,81,84,96,98,99] 1153 NH 3+ Protonated amine rocking [80,86,108] 1002 HNC Carbamate N H rocking [58] 815 NCOO À Carbamate out of plane deformation [61,86] 784 COO À Carbamate deformation [86,108,109] broad band at 2100 cm À1 . [56,67,68,[109][110][111][112] These bands correspond well to the ammonium salt absorption bands at 3200, 2567, and 2166 cm À1 , respectively, in Figure 7. Also, the small band at 815 cm À1 is assigned to the NH 3 + rocking or out of plane deformation.…”

“…In addition, the band at 1456 cm À1 shifts to 1467 cm À1 and significantly increases in magnitude, corresponding to the formation of carbamate. [56,65,67,105,110,112] Amine-CO 2 zwitterion asymmetric and symmetric carboxylate COO À vibrational stretch bands at 1570 and 1434 cm À1 , respectively, are prominent in the 150 min spectrum. There are also COO À carbamate vibrational stretching asymmetric and symmetric bands at 1478 and 1388 cm À1 , respectively, indicating the presence of carbamate at the surface of the 150 min spectrum.…”

“…They also demonstrated, using x-ray photoelectron spectroscopy (XPS), that amine surface activity in an epoxy-amine reacting system is very rapid. Though Synytska, [55] and Croll [56,57] for that matter, allude to carbamate formation at the surface during their reactions, neither conclusively demonstrated it.…”

“…In addition bands demonstrate that there is a stable, detectable zwitterion in the white precipitate, confirming a CO 2 -amine zwitterion pathway for the formation of carbamate. [56,58,59]…”

Statistical modeling of coating lifetimes in disparate environments

“…Finally, Croll has attempted to use Monte Carlo approaches to quantify the amount and locus of damage due to photodegradation and relate those to changes in physical properties such as toughness and gloss loss. [20][21][22] The models detailed above seek to understand (and predict) the performance of specific coatings or materials under arbitrary conditions given some knowledge of the coating's chemical composition or physical properties (diffusion coefficient of water in the material, UV absorption spectrum, coating thickness…) and the kinetics of degradation. While useful for understanding the performance of specific coatings, the coating applicator is typically more interested in the relative performance of coatings compared to one another or the performance of a coating in one location relative to another location.…”