Flame Retardant Fibers
- Flame retardance is achieved by the adhesion of the correct
flame- retardant chemical to viscose. Examples of additives are alkyl,
aryl and halogenated alkyl or aryl phosphates, phosphazenes,
phosphonates and polyphosphonates. Flame retardant rayons have the
additives distributed uniformly through the interior of the fiber and
this property is advantageous over flame retardant cotton fibers where
the flame retardant concentrates at the surface of the fiber.
Super Absorbent Rayons
- This is being produced in order to obtain higher water
retention capacity (although regular rayon retains as much as 100 % of
its weight). These fibers are used in surgical nonwovens. These fibers
are obtained by including water- holding polymers (such as sodium
polyacrylate or sodium carboxy methyl cellulose) in the viscose prior to
spinning, to get a water retention capacity in the range of 150 to 200 %
of its weight.
Micro Denier Fibers
- Rayon fibers with deniers below 1.0 are now being developed and
introduced into the market. These can be used to substantially improve
fabric strength and absorbent properties.
Cross Section Modification
- Modification in cross sectional shape of viscose rayon can be
used to dramatically change the fibers' aesthetic and technical
properties. One such product is Viloft, a flat cross sectional fiber
sold in Europe, which gives a unique soft handle, pleasing drape and
handle. Another modified cross section fiber called Fibre ML(multi
limbed) has a very well defined trilobal shape. Fabrics made of these
fibers have considerably enhanced absorbency, bulk, cover and wet
rigidity all of which are suitable for usage as nonwovens .
Tencel Rayon
- Unlike viscose rayon, Tencel is produced by a straight solvation
process. Wood pulp is dissolved in an amine oxide, which does not lead
to undue degradation of the cellulose chains. The clear viscous solution
is filtered and extruded into an aqueous bath, which precipitates the
cellulose as fibers. This process does not involve any direct chemical
reaction and the diluted amine oxide is purified and reused. This makes
for a completely contained process fully compatible with all
environmental regulations.
Lyocell
A new form of
cellulosic fiber, Lyocell, is starting to find uses in the nonwovens
industry. Lyocell is manufactured using a solvent spinning process, and
is produced by only two companies -- Acordis and Lenzing AG. To produce
Lyocell, wood cellulose is dissolved directly in n-methyl morpholine
n-oxide at high temperature and pressure. The cellulose precipitates in
fiber form as the solvent is diluted, and can then be purified and
dried. The solvent is recovered and reused. Lyocell has all the
advantages of rayon, and in many respects is superior. It has high
strength in both dry and wet states, high absorbency, and can fibrillate
under certain conditions. In addition, the closed-loop manufacturing
process is far more environmentally friendly than that used to
manufacture rayon, although it is also more costly.