Page 98 - Advances in Textile Biotechnology

Enzymatic hydrolysis and modifi cation of core polymer fi bres 79

The fibres had a high melting point (265 °C) and good hydrolytic stability.
Commercial production of this fi bre started in 1949 at ICI under the name
Terylene, and was continued later by Dupont.
The raw materials for PET production are terephthalic acid (TPA) or
dimethyl terephthalate (DMT) and ethylene glycol. There are two produc-

tion routes. TPA is directly esterified to bis-(2-hydroxyethyl)terephthalate
(BHET) whilst forming water. Next, the polycondensation is performed
under continuous release of ethylene glycol. Starting with DMT, the fi rst

step is a transesterification leading to (BHET), accompanied by the forma-
tion of methanol, after which the polycondensation is performed.

Properties and applications of poly(ethylene terephthalate)
PET is a strong and stiff material that is resistant to chemicals, with good
abrasion resistance, a low water uptake (and consequently quick drying),
good resistance to shrinking and stretching and low wrinkling properties.
Depending on the processing and thermal history, PET appears as an amor-
phous or a semi-crystalline material (e.g. during drawing of the fi bres the
polymer chains become oriented resulting in more crystalline fi bres). Amor-
phous PET is transparent and finds its applications in food packaging and

soft drink bottles. Semi-crystalline PET has excellent thermal stability, and
is used in, for example, housings for electrical appliances and recording
tapes. The majority of global PET production is for synthetic fi bers, with
applications ranging from e.g. apparel, curtains, and carpets to e.g. sails,
ropes, nets, tyre cords and fi bre-reinforced materials.

4.1.2 Polyamide
Polyamide (nylon) represents a family of synthetic polymers fi rst produced
in 1935 by Wallace Carothers at DuPont (Guillen, 1986; Stevens, 1999). The
first product was a polyamide-bristled toothbrush (1938), followed more

famously by women’s polyamide stockings (1940). Polyamide 6.6 was the
fi rst commercially successful polymer and it was intended to be a synthetic
replacement for silk. This fibre was used for parachutes production after

the USA entered World War II in 1941, making stockings hard to fi nd until
the war’s end (Burkinshaw, 1995; Guillen, 1986; Moncrieff, 1975).

The US Federal Trade Commission defines nylon fibre as ‘a manufactured

fibre in which the fibre-forming substance is a long-chain synthetic polya-

mide in which less than 85% of the amide linkages (—CO—NH—) are
attached directly to two aliphatic groups’ (Yang, 1989).
Polyamide (PA) is a polymer, which contains recurring amide groups
(R—CO—NH—R′) as integral parts of the main polymer chain. Synthetic
polyamides are produced by a condensation reaction between monomers,

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