ILMA Compoundings September 2016 - 25

VOICES & VIEWS

* Emulsifier
The type of emulsifier (non-ionic vs. anionic), the HLB
(Hydrophilic Lipophilic Balance) of the emulsifier, and the
surface activity (i.e. surface tension-lowering capacity) of the
emulsifier are key characteristics that must be understood.
Over the years, additive suppliers developed emulsifiers
that are specifically designed to be "low-foaming." They
accomplish this by manipulating the chemical structure of
the emulsifier (e.g. adding branching, adjusting the number
of ethylene oxide and propylene oxide groups, adjusting the
position of the polar (hydrophilic) portion of the emulsion
within the molecule).

tendency is higher in soft water (of about 100 ppm total
hardness or less) than it is in hard water. The divalent ions in
hard water tend to "salt-out" anionic emulsifiers present in
the formulation, thereby rendering them inactive, so their
contribution to foam stabilization is minimized. However,
hard water can also reduce their effectiveness as emulsion
stabilizers. Therefore, a balance must be reached in terms
of water hardness so that the water is not so soft that it
promotes foaming, but at the same time not so hard that it
destabilizes the emulsion. The MWF supplier should work
with the end-user to suggest an MWF package that works
optimally for the existing water hardness level.

* Impact of other potentially surface-active components in
the formulation
MWF formulations can be made up of 20 or more
components, and emulsifiers and co-emulsifiers are often
not the only surface-active moieties in the formulation.
Corrosion inhibitors, anti-wear additives, extreme pressure
additives and lubricity additives may sometimes have some
surface activity that could contribute to the stabilization of
foam in MWFs. It is also important to consider any synergistic
effects that may exist between components, especially
emulsifiers and co-emulsifiers that might unexpectedly
enhance foam in the MWF system. For example, it has
been shown in some systems that when the emulsifier and
co-emulsifier both have HLB values that are close to one
another, the effect on foam generation is especially high
relative to when the HLB values are not both in that same
range.

* Antifoam/Defoamer usage
MWFs sometimes have an antifoam incorporated to assist
in controlling foam, and end-users also are able to add
defoamer at their site tankside as a further measure to
control foam. Since the antifoam is typically incorporated
in the MWF package, it is important to make sure that the
antifoam selected is compatible with the MWF package and
that it will not fall out of solution during transport or storage.
The important thing to consider with defoamers, which
are added during the MWF usage, is that in some cases the
addition of too much defoamer can actually lead to more
foam being generated. Therefore, care must be taken not
to overcharge defoamer or do too many "top-offs" with
defoamer.

* MWF concentration
In order to have optimal performance of the MWF, it is
important to use the fluid in the appropriate concentration
range. As one might expect, too much concentrate can
exacerbate foaming because of the excess of emulsifier and
other surface-active components available. MWFs are often
used in the concentration range of approximately 5 to 10
percent. Anything higher than that has a greater chance of
leading to foaming issues.

Each of the factors discussed above must be delicately balanced
when one is trying to ensure optimized performance of an
MWF with minimal foaming. Controlling foam without sacrificing
the integrity of an MWF formulation is not a small task. MWF
suppliers and additive suppliers are diligently working to develop
novel systems to address this issue.

Ford is senior surface scientist, lubricants at Ingevity. She may be
reached at 843-746-8341 or monica.ford@ingevity.com.

* Water hardness
The quality of the water that is being used for a given
metalworking application can play a crucial role in foam
problems encountered during the use of MWFs. Foaming

Compoundings September 2016 * 25 * Vol. 66 No. 9
ILMA Compoundings September 2016

Table of Contents for the Digital Edition of ILMA Compoundings September 2016
