Study of triacetate cinematographic films and magnetic audio track by infrared spectroscopy

Most of the cinematographic film collections stored in film archives are made on a triacetate base, and from the 1950s to the 1980s, a magnetic track was used to record sound. With a large number of archive materials, archives often do not know the chemical composition of film bases, history of use and degradation rates. Therefore, the chemical composition of three films with a magnetic audio track and one representative of the modern film FOMAPAN were investigated by infrared spectroscopy. Selected samples were artificially aged at elevated temperatures and humidity, and the rate of degradation of the film was evaluated by infrared spectroscopy, dimensional changes and gravimetric analysis. Based on the measurements, all of the examined films were made from cellulose triacetate and the binder of the magnetic trackswas cellulose nitrate. To determine the degree of degradation of the binder of the audio track and the triacetate base, a degradation index was created which expresses the ratio of the bandwidths of the characteristic groups in the infrared spectra. It is shown that infrared spectroscopy makes it easy to determine the chemical composition of cinematographic films and to quantify the rate of degradation and the current state of the film base using a suitably chosen degradation index.