How polyester is made – material, manufacture, making, history, used, structure, steps, product, History

Background

Polyester is a synthetic fiber derived from coal, air, water, and
petroleum. Developed in a 20th-century laboratory, polyester fibers are
formed from a chemical reaction between an acid and alcohol. In this
reaction, two or more molecules combine to make a large molecule whose
structure repeats throughout its length. Polyester fibers can form very
iong molecules that are very stable and strong.

Polyester is used in the manufacture of many products, including clothing,
home furnishings, industrial fabrics, computer and recording tapes, and
electrical insulation. Polyester has several advantages over traditional
fabrics such as cotton. It does not absorb moisture, but does absorb oil;
this quality makes polyester the perfect fabric for the application of
water-, soil-, and fire-resistant finishes. Its low absorbency also makes
it naturally resistant to stains. Polyester clothing can be preshrunk in
the finishing process, and thereafter the fabric resists shrinking and
will not stretch out of shape. The fabric is easily dyeable, and not
damaged by mildew. Textured polyester fibers are an effective,
nonallergenic insulator, so the material is used for filling pillows,
quilting, outerwear, and sleeping bags.

History

In 1926, United States-based E.I. du Pont de Nemours and Co. began
research into very large molecules and synthetic fibers. This early
research, headed by W.H. Carothers, centered on what became nylon, the
first synthetic fiber. Soon after, in the years 1939-41, British research
chemists took interest in the du Pont studies and conducted their own
research in the laboratories of Calico Printers Association, Ltd. This
work resulted in the creation of the polyester fiber known in England as
Terylene.

In 1946, du Pont purchased the right to produce this polyester fiber in
the United States. The company conducted some further developmental work,
and in 1951, began to market the fiber under the name Dacron. During the
ensuing years, several companies became interested in polyester fibers and
produced their own versions of the product for different uses. Today,
there are two primary types of polyester, PET (polyethylene terephthalate)
and PCDT (poly-1, 4-cyclohexylene-dimethylene terephthalate). PET, the
more popular type, is applicable to a wider variety of uses. It is
stronger than PCDT, though PCDT is more elastic and resilient. PCDT is
suited to the heavier consumer uses, such as draperies and furniture
coverings. PET can be used alone or blended with other fabrics to make
clothing that is wrinkle and stain resistant and retains its shape.

Raw Materials

Polyester is a chemical term which can be broken into

poly,

meaning many, and

ester,

a basic organic chemical compound. The principle ingredient used in the
manufacture of polyester is ethylene, which is derived from petroleum. In
this process, ethylene is the polymer, the chemical building block of
polyester, and the chemical process that produces the finished polyester
is called polymerization.

The Manufacturing

Process

Polyester is manufactured by one of several methods. The one used depends
on the form the finished polyester will take. The four basic forms are
filament, staple, tow, and fiberfill. In the filament form, each
individual strand of polyester fiber is continuous in length, producing
smooth-surfaced fabrics. In staple form, filaments are cut to short,
predetermined lengths. In this form polyester is easier to blend with
other fibers. Tow is a form in which continuous filaments are drawn
loosely together. Fiberfill is the voluminous form used in the manufacture
of quilts, pillows, and outerwear. The two forms used most frequently are
filament and staple.

Manufacturing Filament Yarn


Polymerization

  • 1 To form polyester, dimethyl terephthalate is first reacted with
    ethylene glycol in the presence of a catalyst at a temperature of
    302-410°F (150-210°C).
  • 2 The resulting chemical, a monomer (single, non-repeating molecule)
    alcohol, is combined with terephthalic acid and raised to a temperature
    of 472°F (280°C). Newly-formed polyester, which is clear and
    molten, is extruded through a slot to form long ribbons.


Drying

  • 3 After the polyester emerges from polymerization, the long molten
    ribbons are allowed to cool until they become brittle. The material is
    cut into tiny chips and completely dried to prevent irregularities in
    consistency.


Melt spinning

  • 4 Polymer chips are melted at 500-518°F (260-270°C) to form a
    syrup-like solution. The solution is put in a metal container called a
    spinneret and forced through its tiny holes, which are usually round,
    but may be pentagonal or any other shape to produce special fibers. The
    number of holes in the spinneret determines the size of the yarn, as the
    emerging fibers are brought together to form a single strand.
  • 5 At the spinning stage, other chemicals may be added to the solution to
    make the resulting material flame retardant, antistatic, or easier to
    dye.
Polyester


Drawing the fiber

  • 6 When polyester emerges from the spinneret, it is soft and easily
    elongated up to five times its original length. The stretching forces
    the random polyester molecules to align in a parallel formation. This
    increases the strength, tenacity, and resilience of the fiber. This
    time, when the filaments dry, the fibers become solid and strong instead
    of brittle.
  • 7 Drawn fibers may vary greatly in diameter and length, depending on the
    characteristics desired of the finished material. Also, as the fibers
    are drawn, they may be textured or twisted to create softer or duller
    fabrics.


Winding

  • 8 After the polyester yarn is drawn, it is wound on large bobbins or
    flat-wound packages, ready to be woven into material.

Manufacturing Staple Fiber

In making polyester staple fiber, polymerization, drying, and melt
spinning (steps 1-4 above) are much the same as in the manufacture of
filament yarn. However, in the melt spinning process, the spinneret has
many more holes when the product is staple fiber. The rope-like bundles of
polyester that emerge are called tow.


Drawing tow

  • 1 Newly-formed tow is quickly cooled in cans that gather the thick
    fibers. Several lengths of tow are gathered and then drawn on heated
    rollers to three or four times their original length.


Crimping

  • 2 Drawn tow is then fed into compression boxes, which force the fibers
    to fold like an accordion, at a rate of 9-15 crimps per inch (3-6 per
    cm). This process helps the fiber hold together during the later
    manufacturing stages.


Setting

  • 3 After the tow is crimped, it is heated at 212-302°F
    (100-150°C) to completely dry the fibers and set the crimp. Some of
    the crimp will unavoidably be pulled out of the fibers during the
    following processes.


Cutting

  • 4 Following heat setting, tow is cut into shorter lengths. Polyester
    that will be
    blended with cotton is cut in 1.25-1.50 inch (3.2-3.8 cm) pieces; for
    rayon blends, 2 inch (5 cm) lengths are cut. For heavier fabrics, such
    as

    carpet,

    polyester filaments are cut into 6 inch (15 cm) lengths.

The Future

Following its introduction to the United States in 1951, polyester quickly
became the country’s fastest-growing fiber. Easy care of the
permanent press fabric made polyester doubleknits extremely popular in the
late 1960s. However, polyester has suffered an “image
problem” since that time, and clothes made out of polyester were
often devalued and even ridiculed. Several new forms of polyester
introduced in the early 1990s may help revitalize the image of polyester.
A new form of polyester fiber, called microfiber, was introduced to the
public in 1991. More luxurious and versatile than traditional polyester,
microfiber fabrics are difficult to tell apart from silk fabrics. Clothing
designers such as Mary McFadden have created a line of clothes using this
new form of polyester. Textile researchers at North Carolina State
University are developing a form of polyester that may be as strong as
Kevlar, a superfiber material used to make bulletproof vests. This type of
polyester may eventually be used as composite materials for cars and
airplanes.

Where To Learn More


Books

Corbman, Bernard P.

Textiles: Fiber to Fabric.

6th ed. Gregg Division, McGraw-Hill, 1983, pp. 374-92.


Encyclopedia of Textiles.

3rd ed. Prentice-Hall, Inc., 1980, pp. 28-33.


Polyester: Fifty Years of Achievement.

State Mutual Book & Periodical Service, 1993.


Periodicals

Fellingham, Christine. “Will You Learn to Love Polyester?”


Glamour,

April 1992, p. 204.

Templeton, Fleur. “Show Me a Bulletproof Leisure Suit, In
Pink.”

Business Week,

July 6, 1992, p. 65.

Thomas, Marita. “At 50 Years, Polyester Gains New Fashion
Vitality.”

Textile World,

December 1993, p. 62+.

Source Article

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