Hand-Mixable Flexible Foam
This foam formulation
is designed to make molded flexible foam parts/sheets/dies/blocks by
hand-mixing or machine casting by the meter dispensing equipment.
The components are stable and liquid at room temperature and ambient
pressure. It requires minimum tooling for a small production or
short runs. The mixing ratio is simple 1:2 by volume. These
properties are ideal in small scale productions for custom foam
applications such as custom seating, padding, and cushioning.
Generally this medium density foam yields firmer foam comparing to
lower density foams. For softer, less firm foam quality, our 6
pound-per-cubic foot formula
recommended. Or for firmer grade, we recommend our firm-flexible
The free-rise density
of the foam is 7.5 pounds per cubic foot, and the cell structure is
open-cell. This is an MDI base water-blown polyester/polyether
hybrid system, and it does not use flammable or
ozone-layer-depleting auxiliary blowing agents
Examples for Applications:
Molded Upholstery Parts
Custom Seating, Padding, and
Custom Packaging of
Physical Properties of the Cured
Foam Density (Free Rise)
Typical Compression Density
Compression Deflection (25%)
Compression Deflection (50%)
Split Tear Resistance
Apparent Surface Hardness
Shore OO 25 - 35
The above data
is typical properties of the 8 LBS/cuft compression foam based
on our in-house test methods.
The data is based on result of our in-house test method on 8
pounds per cubic foot density compression-molded samples at 1”
(Part-A) Curing Agent (Part-B)
Number: MSA-018 PPC-031
Mixing Ratio (Part-A) (Part--B)
Mold/Substrate 100 - 130 ºF
* The ideal
temperature for the mold and substrate is 100 - 130 ºF. However, if
you are using plastic mold, this may not be necessary. For all
metal molds, the temperature needs to be between 100 to 130 ºF.
Pot life (pour
within) 30 - 35 seconds
time 20 - 40 minutes
Complete Cure Cycle:
24 hours at room temperature
(The surface of open-cast foam remains tacky for several
hours at room temperature. Post-curing in an oven at 180 °F
temperature for 1 hour can remove tackiness quicker. Foam made in a
hot mold may need physical crushing to create open cell structure
inside foam. See below for the details.)
We recommend testing
small amounts to see how the material behaves, then develop your
processing method accordingly. In here, the descriptions are for
the manual hand-mixing process. When you process/test, please be
sure to operate in a well-ventilated area or large open area, 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 handling.
you start your test, there is a chance the part-A material being
frozen during the transportation in the cold seasons. Freezing
causes phase separation within the components. In such case, you
need to heat the part-A component to 140 – 160 °F to thaw and
agitate the content by rolling the container(s). Do not open the
container for part-A (MSA-018) until you are ready to use as it is a
moisture sensitive material. Do not use a wooden paint stick as it
contains moisture which contaminates the material. After agitating
the component, keep them at a room temperature above 70 ºF. The
material is most stable at room temperature between 70 °F and 90
°F. Storing the components at a higher temperature accelerate
deterioration of the quality.
Pre-heat the mold and/or substrate to between 100 and 130 ºF.
Apply mold release into the mold. Do not use mold release
containing higher concentration of silicone as it may destroy
the foam surface.
Calculate the total inside volume inside the mold (or the finished
part volume) in cubic feet. Multiply it by the free rise density.
This will give you the weight of the component mixture at the
free-rise density in pounds. Add 5 to 10 % for compression
molding. (See below for more detailed information on compression
molding). This will give you the total weight for the two
Take the correct ratio of part-A and part-B into a mixing cup. Mix
well with a steel or plastic stir stick for about 20 seconds.
Agitate vigorously and thoroughly. Scrape the material off the
side and bottom of the cup as you mix.
The pot life for this
foam formulation is limited, thus there is a limit to the quantity
you can mix well manually by hands. Employing a meter
mixing/casting machine may be best for your production if your part
is large or your production quantity is high.
Cast the mixture into the mold. The mold should be between 100 and
130 ºF. You may use ambient temperature if you are using plastic
mold that does not absorb heat so much. If your mold is of metal or
other heat-absorbing material, the material may not cure properly
under the room temperature. Excess heating also affects the foam
Cure the foam in a mold for at least 20 to 40 minutes before
demolding. Check the strength of the foam surface before
demolding. The surface of the foam may be fragile at this point.
The open top surface may still be tacky, but this is normal. The
tackiness should disappear when the foam is cured completely.
foam should be open-cell structured if you are simply open casting
to make block, die, or sheets. However, if you modify mixing ratio
or molding it in a compression mold, the cells in the foam may not
be sufficiently opened. If the cells in the foam are not opened,
this will lead to substantial shrinkage after the foam is cooled.
Compress the foam with hands to test to see if the foam has an
open-cell structure while foam is warm. If it feels like balloon
that bounces back strongly as you press farther, the foam cells are
not opened. In such cases, physically crush the foam by hands and
try to pop the unopened cells in the foam. This will prevent
shrinking of the foam by cooling. (All flexible foams shrink
slightly. Design your mold accordingly if tighter dimensions are
required. The expected linear shrinkage is 4 to 10% for
compression-molded parts. Higher processing temperature causes
higher shrinkage rate.)
Store at room temperature for 24 hours to complete the cure cycle
Foam 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 to the expected shape. The mold, therefore, needs to be a
closed mold and has to have a capacity to retain the internal
pressure. A simplest compression mold will be an open-top box with
a lid. The lid needs to be clamped to hold the pressure.
The air trapped in
the mold could make large voids if it is not vented. For this
purpose, you need to have very small holes to let the trapped air
escape from the mold. Determine the mold position so that trap air
is pushed toward a corner or sections where the vent holes are.
Small amounts of the foam may squeeze out from the vent holes, which
you can machine off after the part is cured.
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 heat. The heat created from urethane reaction is
required for foam to cure properly. If mold is cold, this heat is
absorbed and the foam does not cure properly. The mold needs to be
heat to 100 to 130 ºF range in case of using metal molds. If your
mold is made of a plastic or elastomeric material, such as silicone
rubber, epoxy, and urethane, this may not be necessary. Please test
and determine the optimal temperature for your mold. Higher mold
temperature increases the shrinkage rate. For tight shrinkage
variation, controlling temperature parameters is very important.
rate” describes the additional amount of material you would put into
the closed mold to create the internal pressure so that the foam
fills the entire inside space of the mold. Typically, about 5 to10
% compression should give enough pressure to distribute the foam
within the mold. Using higher rate makes the foam denser and
stronger. However, it will increase the chance of
closed-cell/shrinkage problem described below.
- Shrinking Problem from Closed-Cell
This material uses a
chemical reaction within the formulation to create CO2 (carbon
dioxide) gas as a source of foaming. This reaction happens when the
material is hot, so this gas is hot when foam is made. As the foam
cools after curing, CO2 gas also cools; as it cools, the volume of
gas contracts. If the cells in the foam are not opened, this CO2
gas takes the whole foam down and shrinks the foam significantly.
It would look like a prune.
To avoid this, you
need to make an open-cell foam structure. This specific foam at the
specified mixing ratio, the foam should have open-cell structure
when it is open-cast to make free-risen foam. However, by
compression-molding, it increases the wall strength of the foam
cells, and this may prevent the cell from opening. This often
happens when the compression rate is high or processed at an
elevated temperature. When this happens, the foam quality becomes
“balloon-like” soon after it foamed while the foam is warm. If
possible, crush this foam at about 30 – 40 minute point while the
foam is still warm. You will hear popping sounds from the foam as
you crush. You can keep crushing until you hear no more popping
sound. This will open the cell inside of foam and will prevent the
large shrinking. The foam also should feel significantly softer
when you compress.
- Preventing Air Voids by Vent Holes
compression-mold a foam product, air inside the mold must be vented
as the foam rises. Other wise you would trap the air at the corners
and it makes large voids. Your compression mold must have vent
holes. (Sometimes, this is erroneously thought that there is not
enough material in the mold. Increasing the amount of material does
not solve this issue.)
You need to develop a
parameter for where in the mold the material should be placed, and
how the mold should be positioned while foam is expanding in the
mold. This will determine where the air in the mold is pushed when
the foam expands.
When you find the
pattern for the air void(s), you would need to put small holes to
where the voids form so you can release the in-mold air. The vent
holes should be small enough so that they will be closed with the
foam after the air is pushed out, so you will still have the
internal pressure. After the part is demolded, you may need to
machine off the small amount of material squeezing out from the vent
- Inconsistent/Large Foam Cells
If you see many small
voids in the foam, this may be because the material is cast in while
the mixture is creaming and loosing its flow. You may be enclosing
more air into the foam while the mixed liquid has a high viscosity.
You may need to finish agitating earlier to avoid enclosing too much
cause is that the material may be touching the side wall before it
is dropped to the proper position for the material to be placed in
the mold. The material on the side wall starts to foam before the
expanding foam from the bottom reaches there. The foam material
stuck on the side wall blocks the passage, which can cause voids.
Place the mold in such position that you can pour the material to
the bottom without touching the side wall of the mold.
If you see
inconsistent foam cells near the mold surface, your mold temperature
may be too high. Lower the mold temperature to near 100 °F and
see if it improves.
I the surface quality
at the areas the foam touches the mold is not smooth, your mold
release may be affecting the quality. Try using different mold
release. Silicone and a few other mold release constituents can
affect the surface tension of foam material, which may destroy the
cell structure. Also, if the mold temperature is too high, it would
affect the cell structure near the mold surface. Try at lower mold
Applications that requires
is not fire-retardant 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 by law. It is the user's
responsibility to conform to the applicable regulations. We also do
not recommend this foam to be used to the applications in which the
foam can be exposed to high temperature or being near an ignition
fire retardant additives, this foam may be modified to
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.
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 will be ruined. This reaction is
non-reversible. Soon after opening a can and dispensing the
content, nitrogen gas or argon gas 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 70 and 90 ºF.
component is hygroscopic. If the material is exposed to ambient
air, it may absorb moisture. Moisture contaminated part-B material
may become source of degradation or excessive bubbles in the
product. Avoid exposure of the material to air. Purging the empty
space in the container with nitrogen gas or
negative-40-degree-due-point dry air is also recommended to prevent
moisture contamination of part-B as well. The storage temperature
should be at a room temperature between 65 and 90 ºF.
component materials are industrial-grade chemicals. Please keep
them in a secure place and prevent access from any unauthorized
individual. The personnel who handle these materials need 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.
using this material, please 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
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.
questions, please contact Northstar Polymers.
All of the statements, recommendations, suggestions, and data
concerning the subject material are based on our laboratory results,
and although we believe the same to be reliable, we expressly do not
represent, warrant, or guarantee the accuracy, completeness, or
reliability of same, or the material or the results to be obtained
from the use thereof, neither do we warrant that any such use,
either alone or in combination with other materials, shall be free
of the rightful claim of any third party by way of INFRINGEMENT or
the like, and NORTHSTAR POLYMERS DISCLAIMS ALL WARRANTIES, EXPRESS
OR IMPLIED, OF MERCHANTABILITY and FITNESS FOR A PARTICULAR
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