Performance Apparel Markets - Grado Zero Espace Srl

Performance Apparel Markets, 1st quarter 2006
Seamless knitting and stitch-free technologies
—polyester, polyethylene,
polypropylene, urethanes
and PVC
At least 60% of the material
must be thermoplastic,
although thermoplastic
tape or film can be used
Some use tape or film to
ensure seam integrity
Welding takes place as a
result of the high
frequency mechanical
motion of a vibrating
horn and compression
between it and a drum
Welding by high
frequency radiation uses
electrodes to raise the
temperature by dielectric
heating
But not all materials can
be heated in this way
The electricity causes
molecules in dipolar
materials to oscillate
PVC and polyurethanes
are the best
Other terms are dielectric
or radio frequency welding
● polyester;
● polyethylene;
● polypropylene;
● urethanes; and
● polyvinylchloride (PVC).
Normally, at least 60% of the material to be ultrasonically welded
must consist of thermoplastic materials. If not, seams produced using
ultrasonic welding have to be reinforced with thermoplastic tape or
film.
However, some manufacturers use thermoplastic tape or film in any
event during ultrasonic heating in order to ensure seam integrity.
Materials are placed between a vibrating horn and a rotary drum
which has a pattern of raised areas. Welding takes place as a result of
the high frequency mechanical motion of the vibrating horn and
compression between the horn and the drum. This action creates
frictional heat at the point where the horn is in contact with the
materials.
WELDING BY HIGH FREQUENCY RADIATION
Welding by high frequency radiation uses electrodes to raise the
temperature by dielectric heating. Dielectric heating is the heating of
an insulator—in this context the insulator is the fabric or the
thermoplastic film—by a high frequency electric field. Such welding
uses a frequency of 27.12 MHz.
Not all materials can be heated in this way, however. The process
relies on certain properties of the fabrics which cause the generation
of heat in a rapidly alternating electric field.
The electricity causes the molecules in dipolar materials, such as some
thermoplastics, to oscillate. This oscillation may then be converted
into heat, which facilitates the welding of the materials.
Materials such as polyvinylchloride (PVC) and polyurethanes are the
best types for this technique.
High frequency welding is also known as dielectric welding, or radio
frequency welding.
SEAMLESS KNITTING
Seamless knitting enables
garments to be made with
no or minimal sewing-up
Overall, seamless knitting is an important development in and for the
knitting industry. It provides the wherewithal to manufacture whole
garments with no, or minimal, sewing-up.
© Textiles Intelligence Limited 25