• Top library match: EVA PE=1-9 #65

1. reference library comparison identifies the sample as EVA PE=1-9, an ethylene‑vinyl acetate copolymer, with high confidence (83 %). The FTIR spectrum displays a dominant pattern of aliphatic hydrocarbon chains together with a strong ester carbonyl band, supporting the ethylene‑vinyl acetate backbone. A set of weaker but clearly resolved amide bands at 1555 and 1237 cm⁻¹ points to the presence of a secondary amide‑containing or protein‑like constituent, which is not typical for pure EVA. These amide features mirror patterns observed in chitin/protein biopolymer references, suggesting C-O‑formulation, bio‑based additive, or surface contamination.

• Pure EVA does not normally exhibit amide bands; the amide signals at 1555 and 1237 cm⁻¹ require a secondary nitrogen‑containing component not explained by the vinyl acetate structure alone.
• The analogical literature evidence associating the 1555/1377/2849 cm⁻¹ triplet with chitin/protein spectra [S2] underscores the multi‑component nature of the sample.
• The origin of the amide/protein contribution remains uncertain – it could originate from a bio‑based additive, a nitrogen‑containing stabiliser, or surface contamination.
• Part of the spectral interpretation relies on analogical literature sources; assigning the amide features to a specific protein or amide polymer requires additional confirmatory analysis.

Recommended next steps: Perform elemental analysis (e.g. CHN) to quantify nitrogen content and confirm the presence of amide/protein material. Run a complementary technique such as pyrolysis‑GC‑MS or thermogravimetric analysis coupled with FTIR (TGA‑FTIR) to identify the nitrogen‑containing component. Compare the sample with a reference EVA spectrum to isolate the spectral contribution of the amide/protein fraction by digital subtraction.