What is the chemical composition of cork?
Cork is a natural fiber that has irregular structure, thickness and density. The chemical composition of cork depends on many factors like geographic origin, genetic origin, the dimension of the tree, climatic conditions, soil condition, growth condition and the age of the bark layer. The general chemical composition of cork is around 40% of suberin, 22% of lignin, 18% of polysaccharides comprising cellulose and hemicellulose; 15% of extractables (15%) and other components such as ash, wax, etc.
The cells of cork have hexagonal prism shapes which are arranged in radial rows. The cork material is extracted from the thick protective continuous layer which is formed by dead cells and grows around the stem of the tree. Cork bark contains phellogen tissue which has the ability to reproduce. These tissues produce cells through the surface of the bark and branches of the tree expanding the cross-sectional area.
Cork produced by trees is of two types: the first one is called virgin cork which is the first cork produced by the original phellogen of the tree. This type of cork has irregular structure, thickness and density; and hence it is very hard and crumbles. The other type of cork is the cork which is extracted after 9 years of the virgin cork. The cork which is extracted afterward is known to be of the best quality and has a variety of applications from cork stoppers, agglomerates to shoes.