Cellulose diacetate, sometimes called diacetate, is a synthetic polymer made by treating cellulose with acetic acid. It consists of two acetyl functional groups on each unit of D-anhydroglucopyranose of the cellulose molecule. It was first developed in the United States.
It is fragile since it is based on cellulose. When cellulose diacetate deteriorates, it shrinks and releases acetic acid causing vinegar syndrome.