Adsorption of Acetic Acid Vapors by Inorganic–Organic Nano Materials: Implications for the Inhibition of the “Vinegar Syndrome” in 20th Century Motion Picture Films

Cellulose acetate (CA) motion picture films are subjected to degradation, especially due to the "vinegar syndrome", a de-acetylation process catalyzed by high temperature, humidity, and acidity. Acetic acid is released as a by-product of this reaction and acts as a catalyst that triggers an autocatalytic process. The main aim of this study was to evaluate the use of metal oxide, hydroxide, and carbonate nanoparticles, as well as their composite inorganic-organic systems, for the adsorption of acetic acid and the inhibition of the deacetylation process. Various nanoparticles (Ca(OH)₂, ZnO and CaCO₃) were compared in terms of their ability to adsorb glacial acetic acid vapors through gravimetry analysis, Fourier Transform Infrared (FTIR) Spectroscopy, X-ray diffraction (XRD), and Thermogravimetric Analysis (TGA). The variation in the size and morphology of the nanoparticles was investigated via Scanning Electron Microscopy (SEM), too. Subsequently, the most promising nanoparticles (ZnO) were incorporated into composite organic-inorganic systems, made of Whatman paper (WP) and polyvinyl alcohol formaldehyde (PVF) xerogels, and their ability to adsorb acetic acid vapors was again evaluated. Finally, the performances of both the pure ZnO nanoparticles and the organic-inorganic composite systems as inhibitors of the "vinegar syndrome" were assessed on artificially degraded motion picture films using a specifically developed and validated multi-analytical protocol.