What could cause unexpected FTIR peaks in a polymer degradation study?

[Mark.D]

I’m trying to interpret some unexpected spectral data from my recent polymer degradation experiment, and the absorption peak I’m seeing just doesn’t align with any known byproducts in the literature. I’m wondering if my calibration for the FTIR spectrometer could be off, or if this indicates a novel decomposition pathway I haven’t considered.

[Eric.B]

I’ve chased that kind of thing before. A peak that won’t fit literature often points to drift or a wonky baseline. I warmed up the FTIR, cleaned the optics, and ran a fresh KBr pellet of a standard polymer to sanity-check the wavenumbers; the peak position didn’t line up with the standard, but at least I knew the instrument wasn’t fully miscalibrated.

[TimothyQM]

I did a calibration check with PMMA on the same instrument and used a fresh KBr pellet. The key peaks shifted only a couple of wavenumbers, not enough to explain my unusual band. I still saw the odd absorption in the degraded polymer, so calibration alone didn’t tell the whole story.

[LarryL]

I started doubting the interpretation. Could be moisture or oxidation creating a new band, or maybe a fragment I hadn’t cataloged. I dried the sample, ran a quick ATR scan, and checked for CO2 or water interference, but the feature persisted and kept dodging assignment.

[MatthewM]

Have you tried repeating the measurement on a different instrument or at another lab to rule out instrument artifact?