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++ Semi-Rigid Foam























Northstar Polymers, LLC

3444 Dight Avenue So.

Minneapolis, MN 55406

Tel: 612.721.2911

Fax: 612.721.1009

E-Mail: info@northstarpolymers.com












Northstar Polymers, LLC is a member of Polyurethane Manufacturers Association.


Copy right reserved by Northstar Polymers, LLC 2000 - 2007.  Northstar Polymer prohibits duplication of the contents of this web site for the purposes of public display and/or using on another web site without a written authorization by Northstar Polymers, LLC.





2.5 lbs/cuft Density Semi-Rigid Foam


MPP-R02C is semi-rigid foam formulations for molded foam products. It is closed-cell light foam with some structural integrity. Unlike rigid polyurethane foams, the physical properties of a cured product have some flexibility so it resists cracking and chipping and cracking with an impact force. This foam may be used in production of small to medium light parts with some structural integrity.

Processing Parameters


Component Typical Properties

  Prepolymer (A) Curing Agent (B)
Product Code: MPN-023 PAC-004
Specific Gravity: 1.173 0.993
Equivalent Weight: 225.9 39.8
%NCO 18.6 n/a


Mixing Ratio:

  Part-A :Part-B
Volume Ratio: 4.000 :1.000
Weight Ratio: 1.000 :0.212


Stoichiometry NCO/OH = 1.000/1.200
NCO Index: 0.833

Processing Temperature:


Part-A: Ambient
Part-B: Ambient
Mold/Substrate: Ambient
Post Cure Oven: 80 -100F

(Mold may need to be heated to 100 110 F if aluminum or steel mold is used.)


Cure Pattern:

Mixing time 10 - 15 seconds by hand batch
Pot life (pour within) 30 - 40 seconds
Demolding time 40 - 60 minutes with mold temperature 110 F
Complete Cure Cycle:  1-2 days at room temperature


Recommended Processing (For Hand-Mixing Test):


We recommend testing small amounts to see how the material actually behaves, then develop your processing method accordingly. 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. Please read the Material Safety Data Sheet for details on the safety and handling.

Before you start your test, there is a chance the part-A material being frozen during the transportation specially in cold days in winter. This may cause separation within the components. In such case, you need to heat the part-A component to 140 F to thaw and agitate the content by rolling the container or with a drum mixer. Do not open the container for part-A until you are ready to use as it is a highly moisture sensitive material. Use dry nitrogen gas to purge the empty space and re-seal when storing. Do not use wooden paint stick as it has moisture within, which to contaminate the material. After agitating the component, keep the component in a room temperature above 70 F. These materials will not freeze at room temperature. Storing the part-A component at a high temperature accelerate deterioration of the quality. Part-B component may freeze under a very cold weather. Part-B can be thawed by leaving it at room temperature for a few days or heat it to 140 F; agitate after it is thawed.


If you are using an aluminum mold or steel mold, you need to pre-heat the mold and substrate to between 100 and 110 F. The material creates heat from a chemical reaction. This heat is needed to cure the material. If the material is directly in contact with a large heat absorbing material, such as aluminum mold, steel mold, or other metal/stone object, this heat is taken away from the foam to cure.


Heating the mold too hot could lead to excessive shrinkage of the foam after it is cooled. Keep the temperature within 100 to 120 F range if auxiliary heating is needed.


Apply mold release into the mold. Do not use silicone-base mold release as it destroys the foam surface.


Take the correct ratio of part-A and part-B into a mixing cup. (How much material to be put into the mold is a very important factor.  See the compression molding section about how to determine the amount to pour into.)  Mix well with a steel or plastic stir stick for 10 - 15 seconds. Agitate vigorously and thoroughly. Scrape the material off the side and bottom of the cup as you mix.


The pot life is short. There is a limit to how much of this material you can mix well by hands. Employing a meter mixing/casting machine may be best for you production if your part is large or the required quantity is high.


Cast the mixture into the mold. (See the following section for compression molding.)


Cure the foam in the mold for at least 40 minutes before demolding. Please check the strength of the foam surface before demolding. The foam is still fragile at this point. Conduct your evaluation test at least 24 hours after the mixing. The open-top surface may still be tacky at this point, but this normal. If you have a thin section that is structurally weak, you may need to leave it in the mold for a longer time.


Store at room temperature for 24 hours to complete the cure cycle before evaluation.
Because of its partially closed cell structure, the foam will slightly shrink after it is cured. If you part requires tighter tolerance, you may need to machine the part or modify your mold to compensate the shrinkage.


Compression Molding


Since the liquid mixture does not fill the mold, the foam needs to fill the mold space with its expansion pressure. By slightly larger amount of foam into a closed mold, you can obtain a better resolution from the mold. The expansion pressure of the foam sends the foam material to fill the mold to the expected shape.


For example, to determine the amount of material needed to create 10% compression rate, calculate the internal volume of your mold in cubic foot then multiply the density value of the foam to obtain the weight in pounds for total amount of material; and then, multiply 1.1 to give compression.  See following equation as summary:


(Final Part Volume in cubic feet) x (Foam Density) x (1 + (Compression rate %)/100)

=  (Amount of total material needed in pounds)


The mold needs to be close mold with 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 by c-clamps or furniture clamps to hold the pressure. The air trapped in the mold could make large voids if it is not released. For this purpose, you need to have very small vent holes to let the trapped air escape from the mold. You can actually try foaming the material to see what parts of the mold have tendency to trap air; then create vents to those places. Change position of the mold to choose the mold position that works best for your part to release the in-mold air.


The mold material can be metal, plastic, or elastomeric material. Mold surface needs to be slick and smooth as foam could stick to rough or porous surface. Metal molds tend to absorb the heat. Heat created from the 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 110 F in case of 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. You may need to machine off the small amount of material squeezing out from the vent holes.


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. If creamed material is mechanically stirred, it may trap air and make those bubbles. To prevent this, try casting the material within the pot life or before the material is too thick.


If your mold is thin and pouring the material from a narrow end, the material often touches the side wall of the mold.  If this happens, the foam starts to cream/foam from the side wall and block the passage of in-mold air; this can also create air pockets. Try not to get the material on the side wall when you are pouring the material in the mold. Changing the position of the mold or vacuum assisted injection from the bottom of the mold may help alleviating this problem.

Other Information


Applications that requires fire-retardant property:

This foam 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 source.

By adding 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.




Part-A 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 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 70 and 100 F.

Part-B component may be 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 F.




The 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.


Whenever 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 fume.

Direct 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.

Notice: 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 PURPOSE.






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Northstar Polymers, LLC

3444 Dight Avenue South

Minneapolis, MN 55406

Tel: 612.721.2911

E-Mail: info@northstarpolymers.com