Page 40 - Curriculum Visions Dynamic Book

Polyester fibre and film
Polyester is a carbon-chain material that is widely used as a synthetic fibre, and it can also be stretched out to make a film. It is not a natural filament as, for example, cotton or wool. Instead, it is pushed out, or extruded from a liquid through find holes in a machine (called a spinneret) and then
pulled into long filaments.
Polyester is a synthetic fabric made from
woven filaments. It has been designed to
be strong (it will not break easily when being woven on a machine), to stand up
to many machine washes and to be easy
to dye, so that it can be made into many colours. It will also stretch, and so be more comfortable for the wearer. The filaments can then be blended with natural fibres
(to give more wear resistance to natural materials) or used on their own.
Some special forms of polyester fibres are given a hollow cross-section. This
gives them the property of being good
at insulating yet lightweight, so they can
be used for warm clothing. Another form
of polyester is made of microfibres, which make a mesh that keeps wind and water out, yet allows body moisture to seep through.
 Hollow and microfibre polyester is widely used in clothing. In the case of sportswear the materials have to be waterproof and yet allow body moisture
out. They have to resist the scuffing that
comes from a fall, and they have to be lightweight so they
do not unduly restrict movement.
 To make fibres, liquid polymer is extruded. The polymer typically arrives in the form of pellets, which are then heated to make a liquid. The liquid is then extruded through fine nozzles in the spinneret so that filaments (single strands) of plastic emerge. These are cooled and rapidly solidify so they can be twisted together to make a fibre.
Plastic pellets are dispensed from a hopper.
Pressurised heating chamber.
Polyester fibre
Spinneret
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