Room-Temperature Curable Microcellular Foam
foam polyurethane formulation is designed to yield closed-cell
microcellular foam by either hand-mixing or machine casting method
at room temperature. The components are liquid at room temperature.
It is designed to be used in compression molding process with 10% or
higher compression rate. For a small quantity, this can be batched
manually by hand tools. This can also be cast with a multi-component
meter-mixing/dispensing machine. The free-rise density of the foam
is 23 pounds-per-cubic-foot.
Curing Agent (B)
ratio can vary within 3-5 %. Higher ratio of part-B will make it
slightly more flexible. Always calibrate your meter mixing equipment
Stoichiometry NCO/OH = 1.000/1.106
NCO Index: 0.904
100 – 120 °F
* The ideal temperature for the mold/substrate is 100 - 120 ºF.
However, if you are using plastic mold, the mold may not need to be
heated. For all metal molds, the temperature needs to be between 100
to 120 ºF.
10 seconds minimum by hand batch
Pot life (pour within)
15 - 20minutes with mold temperature 110 °F
Complete Cure Cycle:
48 hours at room temperature
We recommend testing small amounts to see how the material behaves,
and then develop your casting method accordingly. When you batch,
please be sure to operate in a well-ventilated area or large open
area with a good air circulation, wear rubber gloves, long sleeves,
and protective eyeglasses to avoid skin/eye contact. Read the
enclosed Material Safety Data Sheet for details on the safety and
Before you start your test, there is a chance the materials being
frozen during the transportation when the whether is cool. This may
cause separation of the constituents within the components. If in
such case, you need to agitate the components in the cans. If
MSA-018 arrives with some gel-like material in the container, it is
likely the material has been exposed to some low temperature. In
this case, heat the content to 140 – 160 °F and stir to re-blend the
material in the container. You may use a drum mixer at medium speed
for 15 to 20 minutes to agitate the material in a drum. After
re-blending, keep it at a room temperature above 72 ºF. MSA-018 will
not freeze at room temperature.
For small samples: Do not open the can for part-A (MSA-018) until
you are ready to use as it is a moisture sensitive material. Lightly
shake the unopened can to agitate the content. You can open the can
for part-B (PBD-025) and use a metal spatula or knife (or something
dry, strong, and clean) to agitate. Do not use wooden paint stick as
it has moisture within, it may contaminate the material.
The suggested small quantity test procedure follows:
Pre-heat the mold and substrate to between 100 and 120 ºF if needed.
Apply mold release into the mold if needed. Do not use silicone-base
mold release as it destroys the foam surface.
Calculate the total inside volume of the mold (or the finished part
volume) in cubic feet. Divide it by the free rise density. This will
give you the weight in pounds of the component mixture at the
free-rise density. Multiply by 1.1 for 10 % compression rate. (See
below for compression molding). This will give you the total weight
for the two components. Use the specific gravity data above to
calculate the volume ratio if needed.
Take the correct ratio of part-A and part-B into a mixing cup. Mix
well with a steel or plastic stir-stick for at least 20 seconds.
Agitate vigorously and thoroughly. Scrape the material off the side
and bottom of the cup as you mix.
Cast the mixture into the mold and close the mold. The mold should
be between 100 and 120 ºF if using a metal mold. The material may
not cure properly if mold is too cold. (Plastic mold may not need to
be heated.) If the temperature of the mold is too high, it may cause
defect on the foam surface.
Cure in the mold for about 10 – 15 minutes before demolding. Check
the strength of the foam surface before demolding. Larger parts may
demold faster. Experiment to find the optimum de-molding time.
The foam cures at room temperature gradually for about 24 to 48
hours to yield the final physical properties that are good to be
used in the application.
needs to fill the mold space by put slightly larger amount of foam
into the mold. The expansion pressure of the foam sends the foam
material to fill the mold. The mold therefore needs to be a close
mold and has to have some capacity to retain the expansion pressure.
The simplest mold will be just an open-top box with a lid. The lid
then needs to be clamped to hold the pressure. The air trapped on
the top side of the mold could make a large void if it is not
released. For this purpose, you need to have a very small vent (hair
vent) to let the trapped air escape from the mold.
material can be metal, plastic, or elastomeric material. Mold
surface needs to be slick as foam could stick to any porous surface.
Metal molds tend to absorb the heat. Heat created from the chemical
reaction is required for foam to cure. If mold is cold, this heat is
absorbed and the foam does not cure properly. The mold needs to be
heat to 100 to 120 ºF in case of metal molds if metal mold. If your
mold is plastic or elastomeric mold, this may not be necessary as
those materials retain heat better than metal molds.
Compression rate indicates how much more of component material is
put into the mold. The rate indicates the percentage of excess
amount of material to the amount in which to fill the mold using the
foam’s free-rise density. Typically, about 10 % compression should
give enough pressure to distribute the foam within the mold. Using
higher rate makes the foam denser and stronger.
Shrinking problem for closed-cell microcellular foams and semi-rigid
Polyurethane foam uses a chemical reaction within the components to
create carbon dioxide as a source of foaming. Because the gas is hot
when it is created, it contracts when the foam is cooled to the room
temperature. Closed cell foam with flexibility can shrink together
with this contracting gas as it cools. The compression molding
method gives outward pressure to the gas in foam cells to compensate
this shrinking force. If your foam shrinkage is too much, try
increasing the compression rate to compensate. (This does not apply
to open-cell foams and rigid foams.)
foam is not fire-retardant grade foam, and it is not recommended for
applications, which require or should be using fire-retardant grade
materials. The applications such as automotive interior, building
material, and components for some electronic parts often require
fire-retardant grade materials and it may be regulated by laws. It
is the user's responsibility to conform to the applicable
regulations. We also do not recommend this foam to be used in the
applications in which the foam can be exposed to high temperature or
being near an ignition source.
By adding fire retardant additives, this foam may be modified to a
fire-retardant grade foam. The user must test the foam modified with
the fire retardant additives for the fire-retardant property and the
conformance to the applicable regulations. Contact Northstar
Polymers for source information for fire retardant additives.
Storage and Handling
component (prepolymer) contains isocyanate component, which is very
much sensitive to moisture. If it is left in air, part-A will react
with atmospheric moisture and ruined. This reaction is
non-reversible. Soon after opening a can and dispensing the content,
nitrogen gas or negative-40-degree-due-point dry air needs to be
injected to the can to blanket the material. Silica gel or calcium
chloride desiccant filter should be installed to 55 gallon drum-vent
for your drum feeding system. The storage temperature should be at a
room temperature between 65 and 90 ºF. When part-A component
material is reacted with a large amount of water, it may create a
violent chain reaction, which could even start fire. This material
must be stored indoor where there is no chance of contact with a
large amount of water.
Sometimes when the containers are opened many times during the
storage, small amount of moisture comes into the container and start
to react with the component. This contaminated (reacted) byproduct
is usually heavier than the rest of the material. So, old material
may have a settlement of this bi-product at the bottom of the
container. This bi-product settlement is often thicker and cloudier.
Do not mix-in this settlement. Avoid using the settlement at the
bottom of an old container.
storage temperature for both part-A and part-B should be at a room
temperature between 68 and 90 ºF.
Generally, all constituents of the part-B material are compatible
and stay blended in homogeneously. However, if the material is
stored for a long time, some constituent may start to separate. It
is a good practice to agitate the container before dispensing if you
have stored the material for a long time without movement. Avoid
moisture and enfolding excess air when agitating.
component materials are industrial-grade chemicals. Please keep them
in a secure place and prevent access from any unauthorized
individual. The personnel who handles these materials needs to read
the Material Safety Data Sheet (MSDS) for detail information on
safety and handling of the material. The MSDS for each component is
sent with the shipment of the material.
conducting a test or producing your parts using this material, be
sure to operate in a wide-open area with good air movement, or in a
well-ventilated area. Wear rubber gloves, long sleeves, and
protective eyeglasses to prevent skin/eye contact of the material.
When your operation involves heating or spraying of the material, we
recommend, in addition to the above, installation of a proper
ventilation system and using a half-face respirator recommended for
the use to prevent inhalation of the fume.
contact of polyurethane raw materials to skin/eye, as well as
ingestion may lead to health problems. No eating or smoking should
be permitted at the working area. The operator should wash hands
well with soap and water after handling the materials. Please refer
to the MSDS for each component for the detailed health information.
part-A material is exposed to a low temperature; the constituent
material may freeze and separate within. During the cold seasons,
the material may arrive frozen after traveling in a cold truck. If
you see gelling within the material after the material has arrived,
it is likely the material has been frozen. If the material has had a
chance to be frozen, you need to thaw re-blend. Heat the container
so that the content is about 140 °F, then agitate content gently to
re-blend before dispensing any from the container. Part-B material
has less chance of freezing or separation.
For any questions, please contact Northstar Polymers.