Rayon
Rayon is one of the most peculiar fabrics in commercial use today.
Strictly speaking, it is not an artificial fiber, because it is derived
from naturally occurring cellulose. It is not, however, a natural
fabric, because cellulose requires extensive processing to become rayon.
Rayon is usually classified as a manufactured fiber and considered to
be “regenerated cellulose”.
Rayon is the oldest manufactured
fiber, having been in production since the 1880s in France, where it was
originally developed as a cheap alternative to silk.
Dupont Chemicals acquired the rights to the process in the 1920s and
quickly turned rayon into a household word, churning out yards of the
cheap, versatile fabric. Rayon drapes well, is easy to dye, and is
highly absorbent, although it tends to age poorly. Many rayon products
yellow with age and pill or form small balls and areas of roughness
where the fabric is most heavily worn.
Rayon is used in a variety
of textile applications, including shirts and skirts, and appears in
both woven and knitted forms. The fabric has gained an unfair reputation
because it is frequently used in cheaply constructed garments that do
not stand up to heavy wear. However, rayon is an excellent, nicely
draping alternative to silk and is frequently used in evening gowns and other flowing garments.
The manufacture of rayon begins with cellulose, frequently extracted from wood pulp,
although any plant material with long molecular chains is suitable. The
cellulose is steeped in caustic soda, which concentrates some of the
cellulose into soda cellulose, which is then rolled or pressed to remove
excess soda solution. After pressing, the cellulose is shredded into a
substance called white crumb.
The white crumb is allowed to oxidize, forming shorter molecular chains, and treated with carbon disulfide. The soda cellulose reacts with this substance, forming yellow crumb
due to inorganic compounds that emerge during the chemical process.
This yellow crumb is dissolved in a caustic solution, which relaxes the
hydrogen bonds in the cellulose, producing a highly viscous substance.
This substance gives its name to the manufacturing process, called the viscose process.
This viscous fluid is allowed to age, breaking down the cellulose
structures further to produce an even slurry, and then filtered to
remove impurities. Small air pockets are forced out to ensure a strong,
even fiber, and the mixture is forced through a spinner, which forms
many even strands of fine thread that enter a setting solution to form
cellulose filaments: also called rayon. The rayon is stretched to form a
strong, even bond, washed, and then formed into rayon fabric.
This complex process results in a great deal of environmental
pollution, inspiring a drive to clean up the industry. The rayon
industry has also suffered from the development of cheaper artificial
fabrics with a much shorter manufacturing process, such as nylon.
Rayon is frequently blended with true synthetic fabrics for various
applications, and it is advisable to follow individual care labels on
rayon garments, as these blends have specific handling needs.
Nylon
Nylon is a synthetic fabric made from petroleum products. It was developed in the 1930s as an alternative to silk,
although it quickly became unavailable to civilian consumers, because
nylon was used extensively during the war. Nylon, like many synthetics,
was developed by Wallace Carothers at the Dupont Chemical company, which
continues to manufacture it today. Nylon is valued for its light
weight, incredible tensile strength, durability, and resistance to
damage. It also takes dye easily, making nylon fabrics available in a
wide array of colors for consumers.
Today, nylon is among the many polymer
products in common daily use throughout the world. It is the second
most used fiber in the United States, since it is so versatile and
relatively easy to make. Like most petroleum products, it has a very
slow decay rate, which unfortunately results in the accumulation of
exhausted nylon products in landfills around the world.
Nylon is made through a chemical process called ring opening polymerization,
in which a molecule with a cyclic shape is opened and flattened. Other
forms of nylon are made through the chemical reaction between two
monomers: adipoyl chloride and hexamethylene diamine. When stretched,
nylon fibers even out, thin, and smooth until they reach a point at
which they have no more give, yet are still very strong. Therefore,
after nylon is extruded in a thread form, it is drawn or stretched after
it cools to make long, even fibers. Before drawing, nylon has a tangled
structure, which straightens out into parallel lines.
The strength of nylon comes from amide groups in its molecular chain, which bond
together very well. Nylon also has a very regular shape, which makes it
well suited to creating fabrics designed to stand up to intense forces.
In fact, nylon was the primary material used in parachutes and ropes
during the Second World War for this reason. It is also used for
bulletproof vests and other hard wearing items.
Nylon is very sensitive to heat and should be washed and dried on
cool settings. Nylon can also be hung dry, and it is favored by campers
because it dries very rapidly. Nylon is a flexible textile, and as a
result, it appears in a wide range of applications, from clothing to
climbing equipment. Depending on how it is processed, nylon can be
formed into the gossamer-like threads used in stockings or into thick toothbrush bristles.
Linen
Linen is one of the oldest woven fabrics in human history. Made of
fibers from the flax plant, this material was once considered suitable
only for royalty. Purple linen was the material for a king’s robe. The
Bible mentions linen coverings used in the Tabernacle and the Temple,
and references to “fine linen” are found throughout.
Linen is an
expensive fabric to manufacture. Flax is a temperamental plant to grow,
and the quality of the finished linen depends largely on the quality of
the plant itself. The flax fibers are found in the stalk, which is
picked by hand to preserve the fibers’ integrity — another reason flax
is expensive. Separating the fibers is also a long and tedious process
if performed correctly. Some flax is processed on cotton
machines, but this results in a lower-quality finished fiber. Most
fabric flax is grown today in Western Europe, and the finer quality
linen comes from there, as well.
Good quality linen is soft and
largely free of the “slubs” or small knots often associated with it.
Slubs are only found in lesser quality fabric. Linen is moth-resistant
and repels dirt, as well. Linen can absorb and lose water quickly, and
it can also help “wick” perspiration away from the skin — although sweat
can damage the fabric. This quality has made it popular in hot
climates, such as that of Egypt, for thousands of years.
Modern garments made from linen are expensive because of linen’s expensive manufacturing and weaving
process. However, the fabric readily accepts dye, so it can be
manufactured in many colors. Linen is a lightweight fabric, which makes
it suitable for spring and summer wear. It looks crisp, cool and neat,
even on the warmest days. Most linen can also be washed in a home
machine.
Linen is not perfect, however. One of its worst traits is the
tendency to wrinkle. Sit down in linen slacks, and horizontal creases
appear across the front.
Not only is linen wrinkle-prone, but ironing linen is a great deal of
work. The iron must be very hot and should have a steam setting.
Otherwise, the person ironing the linen will need to spritz the fabric
with water to create steam. Linen can also be ironed damp from the
washer. A light spray starch can also be used on linen, and linen must
be ironed on the wrong side of the fabric, or using a pressing cloth, to
prevent shiny spots.
Although durable, linen garments should be hung in a closet, rather
than folded away in a drawer. Linen fibers can break if folded in the
same place too often. Linen also tends to soften with wear and washing,
so any roughness in the fabric will usually smooth out in time.
Slacks, dresses, suits, sport coats and blazers are all common
clothing items made from linen. However, linen was used for sheets many
years ago and is still used for items such as tablecloths. It even has
industrial uses for luggage and upholstery. With its versatility and beauty, linen will certainly continue to be a widely-used fabric for the foreseeable future.
Silk
Silk is a
natural fiber, and the process of collecting and preparing raw silk has
remained largely unchanged over the past 4,000 years. Silk is harvested
from the cocoons of the larvae of the silkmoth, bombyx mori. After harvesting, the silk is processed, woven and dyed.
Several
creatures secrete a form of silk, but their secretions are far inferior
to those of the silkworm, which is the larval stage of the silkmoth.
Many attempts have been made to produce a synthetic silk alternative,
but the results have been poor and the quality much inferior to natural
silk. The silkmoth is native to China, and it was the Chinese, more than
4,000 years ago, who discovered the silk-making process.
Chinese
silk producers kept the origins of this extremely valuable and
sought-after material an absolute secret. At one point, revealing any
part of the silk-making process was an offense punishable by death.
There are no longer any wild silkmoths; they survive solely in
captivity, mainly on silk farms.
Intensive cultivation and
domestication over the course of more than 4,000 years have resulted in
the adult silkmoth evolving into a flightless creature with a fat body
and tiny wings that are unable to lift the moth's
weight. Instead, the adult moth crawls on legs that struggle to support
its weight. The adult moth lives for up to one week, neither eating nor
drinking, its sole purpose being to breed.
Female silkmoths lay up to 500 eggs, which take around two weeks to
hatch into tiny caterpillars referred to as silkworms. The larvae only
eat mulberry
leaves that are chopped into small pieces and given every few hours.
The silkworm grows rapidly, repeatedly shedding its skin until it
reaches 3 inches (7.5 cm). The caterpillar then pupates and begins to
secrete a liquid from two glands on the head; the liquid hardens as it
reacts with the air.
This process is designed to protect the pupa and can take as long as
three days. The secretion is a single, continuous thread and is raw
silk. Once complete, the cocoon is placed into boiling water to kill the
developing moth before it can emerge and destroy the silk. The cocoon
is then carefully unraveled and placed on a large reel. From each
cocoon, the strand of silk measures up to 2,953 feet (900 m).
The fine silk strands are wound together to produce yarn that can
then be woven and dyed. Waste silk, such as flawed or short strands, is
also processed. It is used to make short furnishings or clothing and
items of inferior quality, which is reflected in the cost of the
finished items. Reeled silk is the term given to the material of highest
quality, and it is the most highly prized.
Nanopaper
Nanopaper is a cutting edge variety of paper with a strength of 214 megapascals (MPa), greater than 130 MPa of cast iron and approaching that of structural steel (250 MPa). Typical paper has a strength of 1 MPa.
The nanopaper, developed by scientists at the Royal Institute of
Technology in Stockholm, Sweden and announced via press releases in
early June 2008, gets its strength from trillions of tiny linked
cellulose nanofibers. The cellulose fibers in nanopaper were produced
by making a sludge of cellulose, similar to the way normal paper is
made, but then further breaking it down using enzymes, mechanical
grinding, and chemical treatment with carboxymethanol. The result are
fibers 1000 times smaller than the fibers in typical paper.
These fibers link together in a defect-free matrix, in contrast to the
fibers in traditional paper, which are so large you can see them with a
magnifying glass. This nanopaper beat the prior record of 103 MPa for a
high-strength paper. The first strength tests used strips 40 mm long
by 5 mm wide and about 50 microns thick.
The researchers that developed the nanopaper touted its numerous
advantages in the publicity surrounding its announcement. They foresee
nanopaper being used to replace all grocery bags, providing an
eco-friendly alternative to petroleum-consuming plastic bags. Nanopaper
could be used as a reinforcing agent in plastics in lieu of highly
expensive carbon
fibers. Nanopaper is riddled with large pores, allowing faster drying,
which would decreases the price of any final product that uses it.
The raw material of nanopaper — cellulose — is the most abundant organic polymer
on the planet. This means that nanopaper products could be
substantially cheaper and more useful than products based on more exotic
and expensive-to-produce nanomaterials such as carbon nanotubes.
Nanopaper might even find use as a general-purpose construction
material, as long as mass-production fabrication costs will be as low as
the inventors claim.
Two other materials are less frequently referred to as nanopaper. These include a titanium
oxide nanofiber matrix created by chemists at the University of
Arkansas, which could be used as a fire-retardant covering or pathogenic
filter, and a potassium manganese oxide nanowire matrix created by MIT researchers as a sponge to suck up oil spills.
FROM:
http://www.wisegeek.com/what-is-rayon.htm
http://www.wisegeek.com/what-is-nylon.htm
http://www.wisegeek.com/what-is-linen.htm
http://www.wisegeek.com/how-is-silk-made.htm
http://www.wisegeek.com/what-is-nanopaper.htm
