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Fluting
provides the edge crush (stacking) strength for corrugated. |
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Combined corrugated
board is made of liner-board, or liners, on the outer surfaces, and
corrugated medium in the middle. At the heart of a corrugator are
two corrugator rolls. These gear-like rollers press flutes into the
softened medium fed between them. There are five basic flute sizes-
A.. B.. C.. E.. & F. |
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A-FLUTE
A-flute, the original flute, is the highest flute size, and
therefore, when combined with an inner and outer facing, is
the thickest. With 36 flutes to the foot, A-flute makes the
most of corrugated's cushioning and stacking properties for
fragile and delicate items. Because A-flute offers excellent
stiffness qualities and short column crush resistance, it has
applications across a broad range of customer uses. |
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B-FLUTE
B-flute, the second flute size adopted by the corrugated industry,
has lower arch heights than A and more flutes (50) per foot.
This means that the medium contacts and supports the liners
at a greater number of points, providing a stiff, flat surface
for high quality printing and die cutting and with excellent
crush resistant properties. B-flute is also preferred for high
speed, automatic packing lines and for pads, dividers, partitions
and other forms of inner packing. Complex die cuts and beverage
trays are excellent applications for B-flute as are can cases,
wrap-around blanks, glass-to-glass packs and slip sheets. B-flute
is generally combined with light weight liners but can be used
with heavier facings if the need arises. |
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C-FLUTE
C-flute came along next to split the difference between A- and
B-flute. With 42 flutes per foot, it's thinner than A-flute,
thicker than B, and offers good cushioning, stacking and printing
properties. C-flute is by far the most widely used flute size.
An estimated 80% of today's corrugated containers are made of
C-flute board. |
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E-FLUTE
E-flute has the greatest number of flutes per foot at 94 which
gives it the greatest crush resistance and the flattest surface
for high quality printing applications. The thin board profile
of E-flute (it is one-fourth the thickness of C-flute) reduces
box size and saves storage space. Because of its thin profile
and excellent cushioning properties, E-flute can often substitute
for conventional folding cartons or solid fiber containers.
Examples of E-flute applications include boxes for cosmetics,
fragile glass and ceramic items and delicate instruments. Another
growing end-use is for pizza boxes where the retailer wants
a cost effective container with good graphics and excellent
product protection. |
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F-FLUTE
F-flute, the newest flute, is just a little more than half the
thickness of E-flute and is the newest growth segment in the
corrugated industry. The idea behind the new flute, originally
developed in Europe, is to make packages with lower fibre content.
With F-flute, converters can reduce the total amount of fibre
in the packaging, thereby creating a more rigid box with less
solid waste going into landfills. In Europe, F-flute is being
used for specialty packaging, point-of-purchase displays, jewelry
and cosmetic packages and shoe boxes. In the U.S., the McDonald's
Big Mac clamshell in F-flute has received great attention. Dairy
Queen, too, is using the F-flute clamshell for its "Ultimate
sandwich" and its hot dogs. |
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KRAFT, MOTTLED WHITE
, BLEACHED WHITE
The most obvious difference among linerboards is color. The
three basic colors are kraft, mottled white, and bleached white.
Less apparent, but very important, are differences in grades.
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BASIS WEIGHT
A key defining property of linerboard and medium grades. Basis
Weight is expressed in pounds per thousand square feet, which
explains why huge rolls of paper weighing several tons are called
"42-pound" or "69-pound" or "26-pound."
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MULLEN
TEST
The traditional practice in making corrugated packaging is to
combine different basis weights of liner and medium to meet
a Mullen or bursting test that will handle the job of containment.
While the practice of combining different liners and mediums
continues, increasingly, attention is turning away from basis
weights and bursting strength ... to a measurement of packaging
performance called ECT. |
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EDGE
CRUSH TEST (ECT)
Edge crush test is a measure of combined corrugated board's
ability to withstand crushing to its columns. |
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STACKING
STRENGTH
ECT has become especially important to many buyers and makers
of shipping containers because in their distribution environment,
stacking strength is essential. If your concern is for a package
that holds up well under a stacking load, your focus may need
to be on ECT for stacking strength rather than bursting strength
for containability. |
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HIGHER
RING CRUSH LINERS
In line with this, you should be aware that many of today's
paper mills offer higher ring crush liners. These improved liners
are the product of advanced papermaking technologies, and pound
for pound, they offer stacking strength that's superior to conventional
liners. |
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RECYCLED
LINERS
Another concern many buyers have is for the recycled fibre content
of the boxes they order. Corrugated does a good job here. |
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POST-CONSUMER
WASTE
While some amount of reclaimed fibre is used in virtually all
grades of linerboard and medium, recycled liner and recycled
medium can actually contain up to 1 00% post-consumer waste.
A key source of reclaimed fibre is the corrugated industry itself.
Waste paper and corrugated board are routinely recycled from
corrugator plants and boxmaking operations. The largest and
fastest growing source of reclaimed wood fibre is post-consumer
waste: old corrugated containers (OCC). |
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