History of Lyocell
In the early 1990s, the UK/US based textile manufacturer Courtaulds (now Acordis) developed an innovative technology for producing a biodegradable, 100% cellulose-based fibre from wood. Through this process, water consumption is strongly lowered compared with cotton and the solvent used is 99.6% recyclable.
Lenzing Fibres, another major manufacturer of rayon, has also entered the Lyocell market. This product is marketed as Lenzing Lyocell.
Lyocell was designated by BISFA (Bureau International pour la Standardisation de la Rayonne et des Fibres Synthetiques) as belonging to a new generic class, and was the first new generic fibre group to be approved by the Federal Trade Commission in 30 years.
Lyocell fibres were predicted to have a big future, and industry today has fulfilled this prediction. Garments containing Tencel are available from numerous shops in the UK and US.
The most notable example to date is Levis Engineered Jeans, which are manufactured with a mixture of 70% cotton and 30% Tencel fibre.
Chemistry and Production
The fibres are produced by a process called NMMO, where wood cellulose is dissolved directly in n-methyl-morpholine-n-oxide at high temperature and pressure. The cellulose precipitates in fibre form as the solvent is diluted, and can then be purified and dried. The solvent is later removed and recycled.
The first Lyocell-type fibre to be produced commercially was Acordis Tencel in 1992. These fibres have a higher wet and dry tensile strength than any other cellulosic fibres. They exhibit low shrinkage in water and have a high number of crystalline regions, which gives rise to the characteristic fibrillation. The fibres become abraded in the wet state causing surface fibrils to peel away, but remain attached to the fibre’s surface. The fibrils splitting away from the fibre surface manifest as a frosty-looking surface, preventing the true dyed colour from emerging.
Early on, this was deemed an unacceptable fabric appearance and texture, but enzyme and mechanical treatments were developed to vary the extent of fibrillation, giving rise to special effects such as ‘peach skin’, soft touch, sand-washed and the ‘used’ look.
Potential uses for Lyocell fall into many categories. Woven apparel for sportswear and bedding, due to high moisture absorption and dissipation are foremost. Lyocell fibres can be blended with most natural fibres, and can be dyed with indigo to produce a fabric that looks like denim but has a silky feel - this was not previously possible, with any other cellulosic fibre except cotton.
Acordis and Lenzing are now producing new non-fibrillating versions, called TencelA100 and Lyocell LF, respectively.
GRIEVE, M.C., 1999, New Fibre Types, Forensic Examination of Fibres, Taylor and Francis Publishing, London, 399 – 419.
ACORDIS, 2003, Information from the website of Acordis http://www.tencel.com, April 2003.
Adapted from my research essay entitled "Forensic examination of new fibres" University of Auckland