From choosing the right one to using it right one: the key steps in using potting glue defoamer
To ensure that the potting glue defoamer can achieve the best effect, there are many key points in terms
of selection, addition, use conditions and subsequent treatment.
Selection suggestions
Choose according to the type of potting glue
Epoxy resin potting glue: Epoxy resin potting glue has high strength, high insulation and good chemical
corrosion resistance, and is often used for the packaging of electronic components. Defoamers with good
compatibility with epoxy resin should be selected, such as polyether modified siloxane defoamers, which
can quickly disperse in the epoxy resin system, effectively eliminate bubbles generated during stirring and
curing, and will not affect the curing reaction and performance of epoxy resin.
Organic silicone potting glue: Organic silicone potting glue has excellent high and low temperature
resistance, flexibility and electrical insulation, and is widely used in aerospace, automotive electronics and
other fields. For organic silicone potting glue, organic silicone defoamers can be selected. This type of
defoamer has a similar chemical structure to organic silicone potting glue, has excellent compatibility, can
quickly penetrate into the bubbles, destroy the surface tension of the bubbles, and achieve the purpose of
defoaming.
Polyurethane potting glue: Polyurethane potting glue has good wear resistance, impact resistance and adhesion.
For polyurethane potting glue, non-silicon defoamers, such as polyether defoamers, can be used to avoid the
interference of silicone defoamers on the curing reaction of polyurethane, and at the same time, bubbles can be
quickly eliminated to ensure the performance of the potting glue.
Consider the use environment
High temperature environment: If the potting glue will be used in a high temperature environment, a defoamer
with good high temperature resistance should be selected. For example, some specially modified silicone defoamers
can maintain stable defoaming performance at high temperatures, and will not decompose or fail due to
temperatureincreases, ensuring that bubbles are effectively eliminated during high temperature potting.
Low temperature environment: In a low temperature environment, the viscosity of the potting glue will increase,
and it will become more difficult to discharge bubbles. At this time, a defoamer with good low temperature dispersibility
and defoaming performance should be selected, such as some polyether defoamers, which can still maintain good
activity at low temperatures and effectively eliminate bubbles.
Humid environment: For potting glue used in a humid environment, the defoamer should have good water resistance.
For example, fluorine-modified polyether defoamers can maintain stable performance in a humid environment and will
not be dissolved or diluted by water, thus continuously exerting a defoaming effect.
Addition suggestions
Determine the addition amount
Refer to the product manual: The recommended addition amount of potting glue defoamers of different types and
brands may vary. Generally speaking, the product manual will give the recommended addition range in a specific potting
glue system, such as 0.1% - 1% (by mass). Addition should be carried out strictly in accordance with the requirements of
the manual to avoid insufficient addition leading to poor defoaming effect, or excessive addition affecting the performance
of the potting glue.
Perform a small test experiment: Since the potting glue formula, production process and use environment in actual
production may differ from the conditions in the product manual, it is recommended to conduct a small test experiment first.
In the small test experiment, add the defoamer to the potting glue at different addition amounts (such as 0.1%, 0.3%, 0.5%,
0.8%, 1.0%) to observe the defoaming effect and the impact on the performance of the potting glue, so as to determine the
best addition amount.
Master the timing of adding
Adding in the premixing stage: When premixing the components of the potting compound, a portion of the defoamer can
be added. Adding the defoamer at this time can eliminate the bubbles that may exist in the potting compound raw materials
in advance during the stirring process, and at the same time make the defoamer evenly dispersed in the potting compound
system,preparing for the subsequent defoaming work.
Adding before vacuum degassing: Before the potting compound is vacuum degassed, add an appropriate amount of
defoamer again. Although vacuum degassing can remove most bubbles, some tiny bubbles may be difficult to completely
eliminate through vacuum degassing. Adding the defoamer at this time can further destroy the surface tension of these tiny bubbles,
making it easier to discharge them in a vacuum environment.
Adding during potting: For some large or complex-shaped potting parts, new bubbles may appear during the potting process.
In this case, a small amount of defoamer can be added in time during the potting process to eliminate the bubbles in time and
ensure the potting quality.
Pay attention to the adding method
Slow addition: When adding defoamer to the potting compound, it should be added slowly to avoid adding a large amount
at one time, which will cause the local concentration of defoamer in the potting compound to be too high, forming new bubbles
or affecting the dispersion effect of the defoamer. You can use the method of dripping or adding a small amount multiple times.
Fully stir: After adding the defoamer, it should be fully stirred immediately to make the defoamer and the potting compound fully
mixed and evenly mixed. The stirring speed and time should be adjusted according to the viscosity of the potting
compound and the properties of the defoamer. Generally speaking, the stirring speed can be controlled at 500-1500 r/min and the
stirring time is 5-15 minutes.
Recommended conditions of use
Control temperature
Suitable temperature range: The performance of the potting compound defoamer will be affected by temperature. Generally
speaking, the defoamer can only play the best defoaming effect within a certain temperature range. The use temperature should be
controlled within the range recommended by the defoamer product manual, usually 20-40℃. If the temperature is too low, the
viscosity of the defoamer will increase, the activity will decrease, and the defoaming effect will become worse; if the temperature
is too high, the defoamer may decompose or volatilize and lose its defoaming effect.
Temperature uniformity: During use, the temperature of the potting glue system should also be ensured to be uniform to avoid
local temperatures being too high or too low. The temperature of the potting glue can be adjusted by a heating or cooling device,
and the temperature can be evenly distributed by stirring.
Adjust the stirring speed and time
Stirring speed: The stirring speed has an important influence on the dispersion and defoaming effect of the defoamer. If the
stirring speed is too low, the defoamer cannot be fully dispersed in the potting glue, and the defoaming effect is not good; if the
stirring speed is too high, a large amount of shear force may be generated, which will destroy the structure of the defoamer and
reduce the defoaming performance. The appropriate stirring speed should be selected according to the viscosity of the potting
glue and the type of defoamer. Generally speaking, for low-viscosity potting glue, the stirring speed can be appropriately increased;
for high-viscosity potting glue, the stirring speed should be appropriately reduced.
Stirring time: The stirring time should also be adjusted according to the actual situation. If the stirring time is too short, the
defoamer cannot be fully mixed with the potting compound, and the defoaming effect is not ideal; if the stirring time is too long,
the defoamer may fail or the performance of the potting compound may change. Generally speaking, the stirring time is 5-20
minutes, and the specific time can be determined through small-scale experiments.
Subsequent processing suggestions
Observe the defoaming effect
Appearance inspection: After the potting compound is defoamed, its appearance should be carefully observed. The surface
of high-quality potting compound should be smooth and flat, without obvious bubbles and defects. If bubbles or pitting are
still found on the surface, it means that the defoaming effect is not ideal. It is necessary to analyze the reasons and take
corresponding measures, such as adjusting the amount of defoamer added, stirring speed and time.
Performance testing: In addition to the appearance inspection, the performance of the potting compound should also be tested,
such as insulation performance, sealing performance, heat dissipation performance, etc. If the performance of the potting compound
does not meet the requirements, it may also be related to the poor defoaming effect, and the defoaming process needs to be further
optimized.
Storage and handling of remaining defoamers
Storage conditions: Unused potting glue defoamers should be stored in sealed, dry, cool containers, away from direct sunlight
and high temperature environments. At the same time, pay attention to the storage period and use it in time according to the
requirements of the product manual to avoid the defoamer from expiring and becoming ineffective.
Container cleaning: When handling remaining defoamers, the used containers should be cleaned to prevent the defoamer
residue from affecting the next use. The container can be cleaned with a suitable solvent, then rinsed with clean water and dried.
