Early detection of aircrafts coating system degradation is critical to prevent delamination and complete failure. Development of methods based on spectroscopic techniques are vital because of their potential to be used for in-situ assessment, and therefore early detection. Aircraft coating systems, usually containing polyurethane (PUR), are prone to degradation through microbes and harsh weathering conditions. This study used Attenuated Total Reflectance- Fourier Transform Infrared (ATR-FTIR) spectroscopy to assess fungal degradation of in-house prepared model coating systems. Growth conditions were optimized first for two fungal species, Aureobasidium pullulans and Fusarium spp. on Potato Dextrose Agar medium. Second, model coating systems were prepared on Al-coated glass slides with (A) white Universal bonding primer (Rust Oleum®) coating and (B) white Universal bonding primer + a clear top coat (Dupli-Color®). Third, fungi and the two coating systems were individually characterized using FTIR to obtain corresponding reference spectra. Finally, an accelerated fungal-biodegradation study was conducted by exposing the two coating systems with pre-grown fungi isolates at 28 0C and 80% humidity for ~10 weeks. The ATR-FTIR analysis of the fungal exposed samples showed decrease in the band intensities corresponding to various PUR bands (1726 cm-1 Carbonyl (C=O) species;1466 cm-1 Aliphatic (CH2) stretch PUR backbone; 1240 cm-1 (C=O) + (O-CH2) stretch; 1147 cm-1 C-O-C stretch). Control coating systems were also incubated similarly, but were not exposed to fungi, did not show any decrease in PUR fungal degradation. Fungal exposed samples also showed increase in Amide-I band (1653 cm-1) intensity indicating fungal growth. Data from other microscopy techniques such as Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM) and Raman Spectroscopy will be also discussed. The results from this study will also have broad implications in an array of industries including aircraft and auto industry.

Characterization of fungal degradation mechanisms of organic coatings (polyurethane) using Fourier-transform infrared spectroscopy (FTIR)

256th National Meeting (2018)

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