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PET (also named PETE) is a kind of
polyester material for fiber, injection molded parts, as well as
blow-molded bottles and jars. Special grades are offered with
the required properties for the different applications.
PET is linear thermoplastic
(long-chain molecule consists of repeating units shown as figure
right), white but bluish resin made from terephthalic acid and
ethylene glycol through poly-condensation. PET is supplied by
the resin manufacturers in the form of small pellets, each about
0.05 gram. PET came into prominence in the 1950s as a textile
material. Its strength, temperature tolerance and
wear-resistance made it an ideal replacement for, or addition to
natural fibers such as silk, cotton and wool.
It has good antiosmosis, low water
absorbability and good toughness. PET film's tensile strength is
similar with aluminum film's, and is three times that of PC and
PA film. PET film is transparent. It's tensile strength can
reach 1/3~1/2 of steel's if dealed by oriented draw. It's the
toughest thermoplastic film. It will be burnt with yellow flame
and will burst when burning. And it will continue burning when
away from fire.
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Nowadays PET is still widely used
for these purposes, but when, in the 1970s a marketing need was
identified for larger light-weight, unbreakable bottles to
contain carbonated drinks, PET fit the bill perfectly. Unlike
simple polymers such as polyethylene, PET is not made by a
single stage process, but by the reaction between two chemicals,
purified terephthalic acid (PTA) and ethylene glycol (EG). The
availability of the first of these has dictated the supply of
PET resin in the past, but new capacity coming on stream this
year will ensure more than adequate supplies to meet the growing
uses of PET over the coming years. Related polyesters are
polybutylene terephthalate (PBT) used mainly for engineering
applications, and polyethylene naphtha late (PEN). The latter
offers significant performance improvements over PET,
particularly in terms of barrier properties and heat tolerance.
Since PEN can be blended with PET a range of new 'alloys' is
becoming available for special packaging applications.
As PET (bottle grade) is a kind of
transparent, wear-resisting and corrosion-resisting plastics
with high strength and smooth finish, it is widely used for PET
bottles of mineral water, juice, edible oil, pharmaceuticals,
cosmetics, etc.
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