Development of an innovative chemical methodology for the treatment of cellulose triacetate motion picture films affected by the "vinegar syndrome"

The present work was focused on the setup of innovative, cheap, easy-to-produce and handle and possibly reusable chemical inhibitors for the so-called “vinegar syndrome” that affects motion picture films whose support is made by cellulose acetate (CA). We proposed and characterized several systems based on two strategies: the use of sponge-like systems (1) made of polyethyleneimine (PEI) and/or (2) uploaded with zinc oxide nanoparticles. The intent was to use free amino groups, in the first case, and inorganic nanoparticles, in the second case, to convert acetic acid into ammonium carboxylate and zinc acetate, respectively, through an acid/base reaction. In order to evaluate the performance of our systems, an innovative degradation method to artificially induce the deacetylation reaction on motion picture films based on the exposition to a high acidity saturated atmosphere has been successfully set up. Another fundamental novelty of this work was the development of a multi-analytical protocol able to monitor the chemical alterations of the base supports connected with the occurrence and the evolution of the “vinegar syndrome”. This is a key point of this project, being that this degradation phenomenon, at today, has been mostly investigated by using single techniques that often do not give exhaustive information about all the aspects involved in the progress of the deacetylation process. In particular, its evolution has been monitored by focusing the attention on the trend of the acetyl content, the free acidity and the ratios between the intensities of some FTIR-ATR diagnostic peaks. In addition, TGA analysis and tensile tests gave precious information about collateral degradation pathways that are promoted by deacetylation (i.e. variation in the molecular weight of CA chains and loss of plasticizers). Then, the evaluation of the efficacy of the above-mentioned systems in inhibiting the vinegar syndrome was performed both on real motion picture films on which the deacetylation process has been artificially induced with our degradation protocol and on films naturally affected by the “vinegar syndrome”. The different behaviors of untreated and treated films have been evaluated through the above-mentioned multi-analytical protocol. The results clearly indicate that the chemical approach based on the use of sponge-like systems made by polyethyleneimine and/or soaked with metal oxide nanoparticles set up in the frame of this work is a highly effective and promising tool for the inhibition of the “vinegar syndrome”. If properly developed and applied, in collaboration with motion picture film conservators, it can potentially represent a valid alternative to the procedures that at today are still commonly used for this purpose and that are mainly focused on the slowdown of the kinetic of the process.