Erin Piateski
3-25-99
Pd. 2
Material Report: Nylon
Nylon was the first completely manmade fiber. It was first
discovered by a scientist working at duPont, Dr. Wallace H. Carothers, in
1935. Nylon is a thermoplastic and belongs in the polyamide category of
plastics. Polyamides discolor in sunlight. However, they have excellent
molding and machine characteristics. These attributes have lead to
widespread use of nylon for a host of diverse applications.
There are two ways that nylon can be formed. Nylon is formed of
long chain molecules. When condensation polymerization occurs, these
molecules combine with each other to form more complex chains within their
compound structure. In the other method of formation, the long chain
molecules combine with other compounds. When polymerization occurs, a
residue, usually water, is formed. Different types of nylons can be
created. The only difference in the chemical composition of nylons is the
number of carbon atoms, so the types are named according. Nylon-4 has
four carbons; nylon-7 has seven carbons, and so forth. The primary focus
of this paper will be nylon-6, which was one of the earlier varieties
produced. Each type of nylon has different properties associated with it.
A Nylon Molecule (Nylon-4)
H H H O H O
| | | || | ||
-H-N-C-N-C-C-C-O-H-
| |
H H
In industry, different types of nylon must be produced in
different ways. For example, nylon-6 is created from the base material
caprolactum, which is a conversion of cyclohex none-oximine. The
polymerization process begins when caprolactum is carefully heated in a
steam-jacketed stainless steel container. It is constantly mixed during
the heating process. Then, it is filtered and pumped into a kettle for
polymerization. The caprolactum stabilizes as a super polymer when it is
heated and pressurized in the kettle. Once the polymer has been formed,
the nylon can be put into the desired form, whether extruded into threads,
made into a film, or cast in a mold. The properties of the completed
nylon will be affected by which of these forms it takes immediately after
production.
In contrast, the production of nylon-6.6 is quite different.
First, a nylon salt is formed using a combination of the chemical row
materials hexamethylene diamine and adipic acid. The nylon salt must be
dissolved in water for easy handling, then sent to a spinning mill. Once
processed in the spinning mill, heating the material in large evaporators
creates a concentrated solution. This concentrate is sent to machinery
that acts like a pressure cooker. As a result of the heat, the molecules
in the chemicals combine to form long chains. These chains are called
"linear super polymers". The polymer is pushed out through a slot in the
machinery on to a revolving casting wheel. The stream of molten nylon
resin is deposited on the wheel and sprayed with cold water. The water
hardens the nylon into opaque white ribbons, which are then removed and
put into a chipper to create flakes.
Nylon has many desirable properties in addition to those listed
earlier. In addition to being resistant to heat and wear, nylon is
resistant to abrasion and prolonged contact with many different chemicals,
alkalis, dilute acids, and oxidizing agents. Nylon has high impact
resistance and a high heat distortion temperature, yet it is lightweight
and has a low coefficient of friction. For example, a nylon filament has
a tensile strength of 53000 psi, and doesnÕt soften until exposed to a
heat of 450û F. NylonÕs light weight is evident when considering that it
is about 1/8 the weight of bronze, 1/7 the weight of cast iron, and 1/2
the weight of aluminum. Unfortunately, the tensile strength of nylon is
affected by moisture content. Adding 2% moisture to nylon, combined with
a 6% strain, lowers the tensile strength by about half. However, in the
long run, nylonÕs numerous advantages outweigh its few flaws, making it
one of the most widely used materials in the world.
In addition to its well-known use as a fabric for clothing, nylon
has many other applications. Nylon is widely used for items like gears
and bearings due to its low friction and high wear resistance. In fact,
nylon is often used as a replacement for metals such as bronze, aluminum,
brass, and steel. It is also used to replace wood, rubber, and other
kinds of plastics. Nylon filaments are used for diverse applications such
as surgical sutures, insulation for electric wires, bristles for
hairbrushes, tennis strings, and fishing lines.
Sometimes adding other substances to nylon adds desired
properties. Sometimes the nylon is impregnated with graphite. Adding
other minerals, glass beads, or glass fibers also alters the performance
of nylon.
Bibliography
"Extruded Nylon (Polyamide) Specifications." Boedeker Plastics, Inc.
http://www.boedeker.com/nylone_p.htm (22 Mar. 1999)
"Production of Nylon Fibre."
http://www.texguide.com/news_group/nylonprod.htm (22 Mar. 1999)
"What are Plastics." Association of Plastic Manufacturers in Europe.
http://www.apme.org/htm/plastics.htm (22 Mar. 1999)
"Chapter XIX: Hercules, Hebe and Ganymede." BulfinchÕs Mythology.
http;//www.webcom.com/shownet/medea/bulfinch/bull19.html (14 Jan. 1999)
"Characteristics of the Amazons in Ancient Literature." Amazon Research
Subscriber Network.
http;//www.net4you.co.at/users/poellauerg/Amazons/charact.html (14 Jan.
1999)
Davis-Kimball, Jeannine. "Statues of Sauromatian and Sarmatian Women."
The Center for the Study of the Eurasian Nomads.
http;//www.csen.org/WomenWarriors/Womens.status.html (14 Jan. 1999)
Davis-Kimball, Jeannine. "WARRIOR WOMEN OF THE EURASIAN STEPPES."
Archaeology. http;//www.archaeology.org/9701/abstracts/sarmatians.html.
(14 Jan. 1999)
"The Amazons." Encyclopedia Mythica.
http;//www.pantheon.org/mythica/articles/a/amazons.html (14 Jan. 1999)