I
n today’s fast-moving world of electronic advances and miniaturization, where glass
fibers play a vital role, the hydroenhancement of such glass fabrics processed on Germany-based
Fleissner GmbH & Co.’s AquaTex® machine can have a major beneficial impact.
This new technology enables manufacturers of glass fiber fabrics to achieve a much higher
degree of density and uniform spreading-out of the filament bundles without incurring any breakage
of the fine glass filaments, which can be as small as 5 microns.
Glass Fiber Fabrics
Glass fibers play a key role in electronic market trends, as they are essential in
reinforced fabrics for printed circuits.
The new, even denser crowding on the surface of these circuit boards is directly related to
the growth in video applications, which require even more complex circuits using the least possible
surface area. This has led to the appearance of printed circuits with a sequential build-up to
accommodate the new components fitted flat onto the surface, as opposed to being welded into the
holes.
A glass fabric has a somewhat uneven surface due to the weaving process and the crossover
points between warp and weft. This can open up the risk of connections not being made during the
fabric’s passage into the welding bath.
Fleissner reports the hydroenhancement process on AquaTex can significantly improve this
potential problem area for glass fabrics. According to the company, the process creates an almost
perfect flatness and isotropy because the very fine and extremely uniform water jets open up the
filament bundles and decrease the thickness of the cross-over between the warp and weft.
For 15 years, London-based BBA Nonwovens developed the InterSpun™ process for the
enhancement of woven and some knit fabrics. BBA received several patents worldwide for this
high-pressure water-jet system. In 1999, BBA and Fleissner signed a contract designating Fleissner
as exclusive manufacturer of the AquaTex machine for the InterSpun process. In December 2000, BBA
decided to concentrate solely on nonwovens and sold the patents for this enhancement technology to
the Polymer Group Inc. (PGI), North Charleston, S.C. Fleissner contractually kept the exclusivity
for building the machinery for this process.
From an engineering standpoint, only relatively minor, but important, modifications had to
be made to Fleissner’s AquaJet® high-pressure water-jet system for the entangling of nonwoven
fibers, in order to build the AquaTex system.
The basis of the InterSpun enhancement process is the use of so-called jet strips. Very
small holes, varying between 0.0050 inch and 0.0032 inch, are precisely drilled into these jet
strips in linear progression. The number of these holes varies between 23.6 per centimeter (cm) and
40.9 per cm – depending on the construction of the fabric. These jet strips are positioned at the
bottom of manifolds that span the width of the machine. The number of manifolds depends upon a
variety of factors, such as fabric weight, type of fiber, production speed, and the total energy
that has to be reached to achieve the desired end result.
Clean water is pumped under high pressure – which can vary from 20 to 125 bar (glass fabrics
are usually processed in the low pressure range) – through these holes and then hits the fabric,
which is carried though the machine either by passing around one or more suction drums or on an
endless belt. Approximately 95 percent of the water flows back through an extensive filtration
system – to avoid clogging the holes in the jet strips – and continues to be reused in the
enhancement process.
This high-pressure water-jet treatment achieves the following results:
• Individual filament strands are opened, “bloom,” and effectively are
separated without any breakage; the lower the twist level, the more effectively the filaments can
be spread out.
• The fabric surface is flattened, and the overall structure made more
isotropic.
• The fabric becomes free of physical impurities, such as oils and sizes.
• The warp yarns become evenly spaced from one another, resulting in the
elimination of reed marks and other related defects.
• Uneven tension within the fabric is eliminated.
• Spaces between the individual filament bundles in the warp and weft, and
at the crossover points between warp and weft, are almost completely closed up, provided that
sufficient filaments are available and the fabrics are not too underconstructed.
Fleissner’s AquaTex System produces a flat fabric with evenly spaced warp yarns.
Main Advantages Of InterSpun Enhancement
• The fabric is very clean.
• The surface is much flatter and more isotropic.
• The process is environmentally friendly.
• Certain weave defects are eliminated in the warp direction.
• Improvement in seam strength is possible.
• Yarn costs are reduced because there are fewer ends and picks in the
weaving.
• Elimination of some traditional finishing processes makes the process
more cost-effective.
• Laser drilling can be utilized effectively.
• Fabrics with lower weights per square yard can be produced, allowing for
further miniaturization in electronic controls.
With this new and revolutionary finishing technology, glass fiber fabrics ranging in weight
from 25 grams per square yard (g/yd2) to 200+ g/yd2 can be modified to be used more efficiently in
subsequent operations.
The InterSpun enhancement of textile fabrics on AquaTex machines is an important step into
the future of producing glass fabrics with increased cost effectiveness and higher performance, and
reduced harmful environmental impact.
For more information about AquaTex, contact Fleissner’s Senior Vice President Dipl. Ing. Alfred
Watzl 49 6103/401-265; watzl@fleissner.de.
February 2003
