Unveiling the composition of historical plastics through non-invasive reflection FT-IR spectroscopy in the extended near- and mid-Infrared spectral range

Francesca Rosi, Costanza Miliani, Peter Gardner, Annalisa Chieli, Aldo Romani, Michela Ciabatta, Rafaela Trevisan, Barbara Ferriani, Emma Richardson, Laura Cartechini

Research output: Contribution to journalArticlepeer-review

Abstract

The present research exploits the strengths of external reflection FT-IR spectroscopy to non-invasively study heritage plastic objects through inspection, for the first time, of the wide spectral range including the near- and mid-IR (12500-350 cm −1). Unlike most of previous works on historical plastic objects, reflection-mode spectra were not corrected for the unfamiliar surface reflection profiles to the more recognizable absorption-like band shapes. This avoided data misinterpretation due to ill-suited Kramers Krönig correction when volume reflection is also present or when highly absorbing IR compounds generate Reststrahlen bands. The inspection of the enlarged spectral range allowed the detection of fundamental, combination and overtone bands which provided reliable identification and semi-quantitative characterization of different polystyrene-based co-polymers. Furthermore the variation of the plastic optical properties across the explored spectral range allowed us to sample the plastic materials to different depths in the mid- and near-IR regions, so as to probe the chemistry at the surface and in the plastic bulk, respectively, in a non-invasive manner. This proved particularly useful to observe spectral markers of surface degradation occurring in historical ABS-based polymers.

Original languageEnglish
Article number338602
JournalAnalytica Chimica Acta
Volume1169
Early online date10 May 2021
DOIs
Publication statusPublished - 18 Jul 2021

Keywords

  • Chemical composition
  • Conservation
  • Design objects
  • Heritage science
  • Polymer

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