A diagnostic tool for assessing the conservation condition of cellulose nitrate and acetate in heritage collections: quantifying the degree of substitution by infrared spectroscopy

Heritage Science

Table 1 Applications of cellulose nitrate/cellulose acetate according to the nitrogen content/acetyl content and the degree of substitution (DS) [30, 34]

Polymer	Applications	Nitrogen/acetyl content (%)^a	Degree of substitution^b
Cellulose nitrate	Explosives	12–13.5	2.26–2.76
	Adhesives	12	2.26
	Film base	12	2.26
	Lacquers, coatings	11.2–12	2.02–2.26
	Plastics	10.5–11.2	1.83–2.02
Cellulose acetate	Injection molding	52.1–54.3	2.2–2.3
	Film	54.3–56.4	2.3–2.4
	Lacquers	56.4–59.3	2.4–2.6
	Film and fiber	60.7–62.85	2.9–3.0

^aValues in italic were used for our case studies: cinematographic films and photographic negatives. In the case of the artworks from José Escada, the injection molding values were considered as the original DS
^bThe degree of substitution can be calculated from the nitrogen and acetyl contents (%) by the following equations [12, 35]: DS = \( \frac{{3.60 \times \left( {{\text{\% nitrogen }}} \right) }}{{31. 13 - \left( {\% nitrogen} \right)}} ; \) DS = \( 162 \times \left( {\frac{{3.86 \times \left( {{\text{\% acetyl}}} \right)}}{{102.4 - \left( { {\text{\% acetyl}}} \right)}}} \right) \)