Lyocell is a man-made cellulosic fiber. It is produced by solvent spinning, i.e., regenerating into fiber form out of a cellulose solution in an organic solvent. It is made up of cellulose and derived from plant sources like wood pulp. For the solution spinning of lyocell fiber the wood pulp is first dissolved at 90 to 1200 C in a solvent NMMO (N-methyl morpholine N- oxide) under normal pressure to form viscose solution. The solution thus obtained is then filtered and extruded by means of fine jet into a water bath; here the regeneration of cellulose takes place resulting in the formation of fiber. The cellulose is regenerated after passing through an air gap into spinning bath. Finally, the fiber is drawn off with appropriate stretching followed by washing, drying and winding of the fiber. With the higher spinning speeds it is possible to produce fine deniers.
Properties of lyocell/tencel
It is the strongest of all the cellulosic fibers. It has a reduction of 15% of wet strength and hence gives an edge over the others. Tenacity lies in the range of 38-42 cN/Tex.
The ratio of crystalline to amorphous area is approximately around 9:1.
they are soft and lustrous. They show good drape and fluidity.
they are highly stable at high temperature. It does not melt but starts loosing strength rapidly at 3000 C and finally gets ignited at 4200 C
Tencel is inert to most of the organic solvents.
However, it degrades in the presence of hot dilute or cold concentrated mineral acid.
Alkalies causes swelling at first (max. at 9% NaOH solution, 250C) and then ultimately disintegration