Identification of Plastic Materials in Museum Collections with Infrared Spectroscopy

Plastic objects are polymer-based materials and are becoming integral parts of cultural heritage, especially in architecture and design museum collections. Often these polymers are less well studied and their chemical decomposition has not yet been fully elucidated. The word polymer is derived from the Greek words poly and meros, meaning many and parts, respectively. Identifying the type of plastic is often challenging because plastics are available in a wide range of formulations where base polymers are mixed with organic and inorganic additives. To set up the proper conditions for the storage and conservation of plastic objects it is necessary to understand their composition because of their susceptibility to various environmental impacts (air, moisture, light, heat). The identification of the composition of plastics is therefore the first step in the preservation and conservation of plastic objects. The research focused on fourteen plastic objects from different time periods: the telephone ISKRA ATA 12, the drilling machine EVS, the lamp Lolita, the radio Brionvega, the telephone Iskra ETA 80, a children’s toy boat, a calendar, a children's rattle, a coat hanger, the shelf Kartell, the children's cutlery by Kogoj, the scales Cesar, the waste basket SJM Žaba and the chair Meblo. In this analysis Fourier transform infrared spectroscopy with a diamond ATR crystal (ATR-FTIR) was used for the identification of polymers. ATR-FTIR spectroscopy was shown to be a suitable method for the characterization of polymer materials from heritage collections. The following polymers were identified: Bakelite, natural rubber (NR), polystyrene (PS), polyvinyl chloride (PVC), polyformaldehyde (POM), polyester resin, styrene butadiene rubber (SBR), styrene acrylonitrile (SAN), acrylonitrile-butadiene-styrene (ABS), polyethylene (PE), polypropylene (PP), polyamide (PA).