|ADVANTAGES OF WATER BASED CONTACT ADHESIVES
No Fire or Explosion Hazard
Little or No Health Hazard
Little or No VOC
More Coverage Per Gallon
DISADVANTAGES OF WATER BASED CONTACT ADHESIVES
Not Freeze/Thaw Stable (in most cases)
Adhesive Break Down in Piston Pumps and Regulators
In the past, water based contact were only discussed or
considered when there was a solvent crunch, such as in 1973,
and shops would go back to solvent based contact when the
crunch was over. We are now seeing a major push to water
based contacts, because of the EPA restrictions on the VOC
emissions and the phase out of 1,1,1 trichloroethane.
In water based contact adhesives, there is usually 3-5% of
solvent. The solvent is used by the raw material suppliers
to make the emulsion and this small amount of solvent does
not effect the non-flammability. However, the solvent does
emit an extremely small amount of VOC's (Volatile Organic
Compounds), but levels are not high enough to be concerned
with, and in some cases, not SARA reportable depending on
the solvent used. However, we use V M & P Naphtha which is
not SARA reportable.
Workers will not develop headaches, dizziness, nausea, or be
affected with any of the problems associated with long term
over exposure to solvent based adhesives.
Most water based contacts average a solid content of 49-50%.
This will result in higher coverages per gallon, compared to
solvent based contacts, but not 3-4 times the coverage
boasted by some companies. Water based contacts spray flat
like paint, while solvent based adhesives spray a pebbly or
cob-webbed pattern, which produces highs and lows for the
adhesive to grab to. With water based spraying flat, more
adhesive has to be applies to insure enough adhesive is on
the surface of the laminate and the substrate to achieve a
good bond. It is recommended that 2.0 dry grams of adhesive
be applied to both surfaces using a solvent based contact,
while it is recommended that 3.0 dry grams of adhesive be
applied to both surfaces using a water based contact. By
applying 3.0 dry grams, you will notice an improvement in
coverage, but not by 3-4 time the square footage of a
solvent based contact. Please see the coverage example:
(454grams/lb X Wt/gal X % Solids) / # of Dry Grams Applied
This will yield the number of sq. ft. per gallon single
coverage (all DHPL or all substrate). Divide the sq. ft.
per gallon single coverage by 2 to receive the sq. ft. per
gallon completed bond. 454 is the number of grams in a
pound and is a constant. The number of dry grams applied
for a solvent based adhesive should be 1.8 - 2.0 dry grams
hand spraying, and a minimum of 1.5 dry grams with an
automatic spray. The number of dry grams applied for water
based adhesive should be 3.0 - 3.5 dry grams.
Flammable Spray Grade
(454 X 6.7 X .20) / 2.0 = 304.18 Sq. Ft. per gallon single
(304.18) / 2 = 152.09 Sq. Ft. per gallon completed bond
($6.90 cost/gal) / 152.09 = $0.0454 cost/sq. ft. completed
(454 X 9.1 X .49) / 3.0 = 674.80 Sq. Ft. per gallon single
(674.80) / 2 = 337.40 Sq. Ft. per gallon complete bond
($17.75 cost/gal) / 337.40 = $0.0526 cost/sq. ft. completed
Based on these figures, there is a increase in coverage of
122% by using water based contact compared to flammable
solvent based contact. Pricing figures used are direct
industrial prices and would be higher through a distributor
or retailer. This example also demonstrates that even
though water based is much higher in cost per gallon
compared to a solvent based, with the additional coverage
that you receive, the FINAL cost per sq. ft. with water
based is in the same ballpark of solvent based costs.
The carrier in water based contacts is water. Water is
slower to evaporate than solvents, both flammable and non-
flammable. If water based is allowed to air dry, the dry
times will vary according to the temperature and humidity,
just as it is with solvent based adhesives. The two
variables needed to speed the dry time are AIR MOVEMENT and
HEAT. Air movement will significantly reduce the amount of
time required for the adhesive to dry. Heat combined with
the air movement will also help speed the dry time.
However, you do not want to use heat alone because this
could cause the adhesive to form a skin and trap water which
will soak into the board and possible result in a warp.
Warping can be a problem with water based contact adhesives
since putting water into one side of the board can cause a
change in the dimension of the board. To stabilize the
board and prevent warping, adhesive and a backer sheet
should be applied to the other side of the board. the
chance of warping can be reduced by preheating the
Most water based contacts are not freeze/thaw stable. This
means that one cannot allow them to freeze and then bring
them back to room temperature, agitate, and then use the
product. Once frozen, water based contacts are ruined, they
cannot be reprocessed and they have to be disposed of.
However, with new technology, some companies are
starting to manufacture some water based contacts that are
somewhat freeze/thaw stable. In contrast, solvent based
contacts generally will not freeze. Instead, when they get
cold enough, they will phase, meaning the solids will
settle out of solution. One can warm the adhesive to room
temperature, agitate, and the product can be used again.
The pumping equipment, fluid tips and needles, fluid
channels, and all connections used with water based contact
must be stainless steel. Piston pumps cannot be used with
most neoprene water based contacts because they are not
mechanically stable, and the shearing action of the pump
causes the adhesive to break down. Instead, a diaphragm
pump is recommended. Pressure pots and cup guns are okay.
Fluid regulators on larger systems will also cause a
shearing action which will eventually cause the adhesive to
clog the regulator.
Water based contacts also have a problem with misting. By
atomizing at 60-80 psi, a fog will be floating in the spray
area and the air caps on the guns will constantly become
clogged. To reduce this problem, it is strongly recommended
that and HVLP gun be used, either by conversion gun or
Water based contacts are a viable alternative to solvent
based. Most are made with neoprene rubber, which has a
proven track record and will produce strong permanent bonds.
The application methods are essentially the same and the
only change is in the production scheduling, unless a method
to force dry the adhesive is implemented.