2002 - Volume 1 - JEFF. Journal of Engineered Fibers and Fabrics

TECHNOLOGY WATCH
in making PLA resin. Under the agreement,
the joint venture will supply lactic
acid until Cargill Dow has developed its
own capacity, expected to occur by mid-
2003. This agreement will allow Purac, a
unit of Dutch food Group CSM, nv
(Amsterdam), and Cargill to accelerate
expansion of plants in Brazil and the U.S.
by about 40,000 metric tons per year. This
move will thus insure the availability of
sufficient lactic acid to Cargill Dow to
ratchet up their new polymer plant to full
capacity as soon as possible.
Super-Functional Clothing
Over the past few months the popular
press has described a variety of “Gee
Whiz” items of wearing apparel and other
specialty functional articles that depend
on fibers and textiles for their outstanding
functionality. Nonwoven materials are
involved in some of these developments;
with a little ingenuity and innovation, nonwovens
could certainly be involved in
many more ways, and actually be the key
element in some of these advanced developments.
One such development involves the
storage of body heat to provide a garment
that keeps an individual warm. Most thermal
insulation works by creating voids
which are filled with entrapped air, which
provides the insulation. Air has a limited
heat capacity, however, so the ability to
store heat in an air mass is quite limited.
A material that melts and solidifies at a
temperature close to body temperature can
be used as a much larger heat reservoir.
This development uses waxes that have
melting points that range from 0 degrees
C to about 60 degrees C, broadly spanning
normal body temperature. The waxes are
microencapsulated, to make them easy to
manage and contain. In microcapsule
structures, the wax particles are coated
with gelatin or a similar substance as the
capsule forming element. When the temperature
is above the melting point, the
molten wax in contained within the microcapsule
shell. When the temperature is
lowered, the wax solidifies, again contained
with the microcapsule. During the
process of melting, a definite amount of
heat must be absorbed (Heat of Fusion).
10 INJ Spring 2002
When the temperature is lowered, the
same amount of heat is given off as the
particle freezes.
In contact with a warm body, the
microencapsulated material picks up heat
and undergoes melting and warming of
the wax. When placed in a colder environment,
the capsules give up their heat in
cooling to the melting point and then further
give up the Heat of Fusion as they
solidify. Thus, the capsules are an active
heat source.
In use, the microencapsulated waxes are
added to a coating solution that includes a
polymer dispersion, thickener, and surfactants.
The coating is applied to a fabric
using a knife-over-roll coater and then
dried. Waxes of C-18 and C-20 carbon
atoms are particularly suited for use in
garments, as they have melting temperature
of 28 and 38 degrees C. respectively
— below and at body temperature. Higher
melting waxes may be useful in heat protective
garments.
A somewhat different approach to the
same problem has been used by
researchers at Malden Mills in
Massachusetts, working with textile
experts at the U.S. Army’s Natick
Laboratory. This approach centers on situations
where the amount of heat generated
by the body is inadequate for extreme
environments that soldiers and outdoor
enthusiasts must endure for extended periods.
The solution is this project has been
to develop high-tech jackets that create
their own warmth by means of lightweight
lithium batteries.
Instead of heat being developed from
an electric current running through
embedded wires, a more subtle approach
has been taken. This involves developing
heat within stainless steel microfibers that
are an integral part of the fabric. The
microfibers are thinner than a human hair,
and when blended with conventional
fibers, give a fabric that is as washable,
soft and conformable as a normal fabric.
The electrical power for heating is provided
by small lithium battery that is
affixed to a holder on the exterior of the
jacket. This battery is about the size of a
pocket watch. The current jacket has two
settings; the “normal” setting heats the
fabric around the chest area to 108 degrees
F. for five hours, or on a “high setting,
goes to 114 degrees F. for 2.5 hours. The
heating occurs in the chest area to heat up
the body core where the heart and lungs
are located; if the core, where all of the
blood circulates through, is warm, then the
extremities are satisfactory.
The use of “nanotechnology” — the
science of making electronic and other
devices on the tiniest of atomic scales—
is being explored for application to textile
and fibers, to make “smart clothing.”
Motorola, for instance, is working on
developing clothing that can “talk” to
washing machines to give instructions on
how the garments should be washed, by
relaying the appropriate wash machine
settings.
Burlington is working with Nano-Tex
Inc. to develop fibers that comprise molecular-scaled
sponges that absorb the rancid
hydrocarbons that are responsible for
body odors. The sponges are designed to
release such odors only when they
encounter a detergent in the washing
machine.
DuPont is working with fibers having
unique cross-sections which enable
microscopic “wings” of different materials
to be added to the core fiber, like wings
of a bird; the fabric can then be made to
contract or expand, loosening and tightening
clothing, or changing color as the
wearer desires. This area of “textronics,”
as DuPont likes to call it, will combine
textile and fiber properties with electronics
in some unusual ways. This is an area
where the company hopes it can leverage
its extensive knowledge in chemistry, textiles
and electronics.
Other advanced programs involving
fibers, fabrics and apparel are aimed at
monitoring ill patients, fitness enthusiasts,
sporting participants and military
personnel. Consider installing a GPS system
in a child’s clothing or the clothing
of an Alzheimer patient to assist in determining
location. The potential extension
of such capabilities seems almost limitless,
and nonwoven structures are likely
the ideal for many of these advanced
concepts. — INJ