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Table 2 Assignment of the main spectral changes observed in linseed oil aging and summary of the observed changes

From: New insights into the deterioration of TiO2 based oil paints: the effects of illumination conditions and surface interactions

Functional group Peak position (cm−1) Assignment Observed changes in linseed oil and BaSO4 Observed changes in TiO2
C=O stretch 1776 Peracids, perester, γ-lactones, and anhydrides Small increase in visible and UV–vis light Small increase in visible and UV–vis light
  1736 Ester Used for normalization Used for normalization
  1710 saturated ketones, COOH acid, and aldehydes Minimal increase in linseed oil and BaSO4 samples in UV–vis and visible light; No changes in dark Large increase in UV–vis and visible light; Slight increase in dark, final point for anatase UV–vis shows large increase
C=C 1670–1610 ν (C=C) of β-unsaturated carbonyl compounds Small increase in linseed oil only samples in visible and UV–vis light Strong increase in anatase and rutile pigmented samples in visible and UV–vis light; minimal increase in dark
ν (C–O) Triglycer-ide ester linkage 1000–1300 (main peak at 1168) ν(C–O) in triglyceride ester linkage + νas (C–O) of C–C(O)–O Slight increase followed by decrease in linseed oil only samples, N/A in BaSO4 samples Decrease in TiO2 containing samples in UV–vis and visible light.; No clear change in dark