Performance Apparel Markets - Grado Zero Espace Srl

Performance Apparel Markets, 1st quarter 2006
Seamless knitting and stitch-free technologies
polymer types include polyurethane, polyester, nylon and
polyolefin.
—the thickness or gauge—
—the film’s softening
point, at which it begins to
melt and flow—
—and the melt flow index,
indicating how an adhesive
flows once it has melted
A heat seal press may be
used
During production three
key factors must be met
precisely and monitored—
—heat—
—pressure—
—and time
Ultrasonic welding
involves channelling high
frequency vibratory waves
to build up heat in fibres
It is fast, accurate and fabrics
stay soft and breathable
Ultrasonic welding can be
used on nylon—
● A second property is the thickness or gauge of the film, which
helps to determine its weight. Heavier fabrics require a thicker
film for optimum bonding while lighter weight fabrics require a
thinner film.
● A third property is the film’s softening point—or the temperature
at which it begins to melt and flow. As a general rule, the
minimum set temperature to activate a thermoplastic film is 15°C
above its softening point. Importantly, the film should have a
lower melting temperature than the fabrics being bonded.
● A fourth property is the melt flow index. This is an indication of
how the thermoplastic flows once it has melted. A thermoplastic
with a high melt flow index will flow rapidly after melting
(similar to water) whereas one with a low melt flow index will
flow more slowly (more like honey). High melt flow
thermoplastics penetrate more quickly into fabrics than do low
melt flow thermoplastics, resulting in a better mechanical bond.
In order to activate thermoplastic films, a heat seal press may be
used.
During the production process, three key factors must be met precisely
and monitored to ensure a strong and durable bond: heat, pressure and
time.
● Heat: during production the critical temperature is the glue line
temperature (GLT)—which is the temperature at the interface
between the two fabrics.
● Pressure: this is usually applied by a pneumatic cylinder.
● Time: for the thermoplastic to melt and flow into a fabric
adequately, heat and pressure need to be applied for a precise
amount of time.
WELDING BY ULTRASONIC HEATING
Ultrasonic welding involves channelling high frequency vibratory
waves (typically 20 KHz or more) so that they cause a rapid build-up
of heat in synthetic fabrics. The heat can be used to weld or cut the
fabrics.
Proponents claim that ultrasonic welding is fast, accurate and efficient.
Also, fabrics retain their softness and breathability.
Ultrasonic welding can be used to cut or weld materials such as:
● nylon;
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