• Top library match: Vinyl chloride/vinyl acetate copolymer #322

• The top-ranking library materials do not contain silicon, yet the high-wavenumber cluster shows an excellent match to Si–H stretching vibrations of hydrogenated silicon compounds, suggesting a non-organic component.
• No other silicon-specific spectral features (e.g., Si–O–Si stretches near 1000–1100 cm⁻¹) are clearly resolved, weakening a purely inorganic silicon assignment.
• The cluster between 2000 and 2222 cm⁻¹ remains the primary uncertainty: it can be attributed to either Si–H species (additive, contamination, or functional particle) or to an unusual set of nitrile/combination bands within the organic polymer.
• Without elemental or orthogonal spectroscopic data, the exact chemical origin of this cluster cannot be firmly assigned.

Recommended next steps: Perform elemental analysis (EDS, XPS, or ICP) to establish the presence or absence of silicon and quantify its concentration. Acquire a Raman spectrum to differentiate between C≡N and Si–H vibrations; the polarisability differences should yield complementary information. Use solid‑state ¹³C and ²⁹Si NMR to resolve the organic polymer backbone and any silicon-based domains.