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++Flexible Foam

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What's New?

Viscoelastic 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.








Hand-Pourable Viscoelastic Flexible Foam


VEF-99 is formulated to create very soft flexible foam for variety of custom applications.  The cured foam has a very low deflection even into a deeper depression rate, and it conforms to the object with a viscoelastic behavior.  VEF-99 is liquid polyether based polyurethane, which stays soft at a very cold temperature.


The component materials are low viscosity liquid at room temperature.  The pot-life is above 30 seconds, which allows small amounts to be batched manually without a dispensing machine.  The mixing ratio is set for 1:1 by volume for easy metering.  This makes VEF-99 a more user-friendly viscoelastic foam material for product designers, prototype makers, and short-run part manufacturers.


We have significantly improved the processing issues with our previous viscoelastic foam formulations.  VEF-99 produces more dimensionally stable molded foam parts after the crushing process.  The component materials are more stable in wider temperature conditions for shipping and storage. 


These properties of VEF-99 enable product designers to create unique foam parts to be relatively easily molded to make cushioning parts and many specialty products.  


Demo: Slow Rebound Property of VEF-99 Viscoelastic Foam






Technical Data:


System Code: VEF-99

Component Properties

                                                Prepolymer (A)             Curing Agent (B)

Code Number:                          MPB-028                      PPF-027                      

Specific Gravity:                       1.108                            1.014   

Equivalent Weight:                    290                               268                              

          %NCO                                    14.5 %                          n/a      

          Viscosity (@72F)                    450 - 850 cps                500 - 900 cps               


Mixing Ratio                                         (A)                               (B)


Volume Ratio:                           1.000                            1.000

Weight Ratio:                            1.000                            0.916


                                                NCO                             OH

Stoichiometry:                          1.000                            0.992


NCO Index                               1.008                           


Processing Temperature:


Part-A                                      Ambient

Part-B                                      Ambient

Mold/Substrate*                       100 - 140 F


*Note: The rebounding and compression-deflection properties change when the material is cured at different temperatures.  Foams cured at a higher temperature will have a faster rebounding speed and higher compression-deflection properties.  A variation of mold temperature ranges between 100 F and 140 F should be tested to determine the optimum mold temperature to create the optimum foam quality and mold cycle.


Cure Pattern:


Pot life (pour within)                  30 - 35 seconds

Demolding time                         40 minutes at 120 130 ˚F Mold Temperature**

Crush Time***:                         40 minutes

Complete Cure Cycle:               24 hours at room temperature


**Note:  When processed at a lower mold temperature, it may need a longer time in mold to cure.


***Note: The molded foam part needs to be physically crushed just after demolded to ensure open-cell structure of the foam.  Without this process, closed cells in the foam part will shrink badly as the foam cools off.  If the foam deforms too much after crushing, you will need to leave the foam part in mold for a longer time before crushing or use a higher mold temperature.




Typical Cured Foam Density:


     Free Rise Density:    Approximately 8.5 pounds per cubic foot

     Recommended Compression Rate:    10%

     Typical Compressed Foam Density:    9.4 pounds per cubic foot


      Note: The mold temperature can affect the foam density.




Shrinking Problem with Closed-Cell Structure


This material uses a chemical reaction within the formula to create CO2 (carbon dioxide) gas as the source of foaming.  The reaction happens when the material is hot and the gas is created at higher temperature at an expanded volume.  As the foam cools after curing, CO2 gas also cools; as it cools, the volume of gas contracts significantly.  If the foam cells are closed this CO2 gas takes the whole foam down and shrink the foam; it would shrink like a prune. 


This material creates closed-cell structure at the demolding time, and must be physically crushed to open internal cells to create open-cell structure.  After the foam is cured strong enough to demold, remove the molded foam part and use your hand to push the foam down before the foam part starts cooling.  As you push the foam, you would feel like pushing down a balloon, and at one point, you start hearing popping sounds from the foam.  This opens the cells. The open-cell structure equalizes the air pressures between inside and outside the foam, and prevents the large shrinkage.


The foam part will still have smaller shrinkage after crushing.  Test to measure the shrinkage on your part and design your mold to compensate the shrinkage.   This material may not be appropriate to mold parts with a high precision requirement.




Other Handling Information


Storage/Handling Information for the Component Materials





Part-A (Isocyanate Prepolymer) Component


Part-A component (prepolymer) contains isocyanate component, which is highly sensitive to moisture.  If it is left in the open air, part-A will react with atmospheric moisture and will be ruined.  This reaction is non-reversible.  Soon after opening the container to dispense the content, dry nitrogen gas or argon gas needs to be injected to the container to purge and blanket the top space. Please consult Northstar Polymers for nitrogen gas set-up information.


For gravity feeding system from a 55-gallon, silica gel or calcium chloride desiccant filter(s) should be installed to the vent-hole of the drum. A valve to inject dry nitrogen gas can be installed instead.


Store the containers a dry indoor storage within the temperature range between 72 and 90 F. Avoid direct sunlight.


The material has been tested for the old temperature stability at 32 F for a few days.  However, when the outdoor temperature is below 32 F during transportation, there is a chance of freezing.  The frozen material must be immediately thawed to avoid permanent damage from freezing.  If the material color is opaque with the consistency of thick liquid, gel, waxy, or solid, the material requires immediate thawing.  The container should be put into an industrial oven at 180 F until the material temperature is 140 F or the color of the material is clear with smooth liquid consistency. Storing frozen material more than a few days will cause a permanent damage to the material, and it will not be returnable or refundable.


If a large amount of water mixes with a large amount of isocyanate base materials, the chemical reaction may produce a large amount of CO2 gas and heat to create a hazardous condition. Keep the storage area free of water.


Under a certain combination of heat, catalyst (basic chemicals), amounts of reactive materials, and some other favorable conditions for the reaction, the water (or alcohol/glycol/amine) to isocyanate reaction can reach a dangerous state of accelerated reaction.  The accelerated reaction may create a very high temperature condition. The thermal decomposition of isocyanate based material by extremely high temperature or fire can produce toxic gasses and smokes. Please be sure that the containers are stored in dry indoor storage, away from source of large amount of water. 


If a leak is found in a drum, please place the drum in such a position that the leaking part is at the highest part of drum so that the content no longer leaks out. Cover the leaking area with dry towel to prevent air from entering. If possible, transfer the material into new container(s) with nitrogen purge.  If moisture enters into an isocyanate container from a small leakage, CO2 gas may be produced to gradually pressurize the container.  If pressure built up is suspected, open the bung (or cap) very slowly to release the pressure before you change the drum position.  



Part-B (Curative) Component


Part-B component is hygroscopic.  If the material is exposed to ambient air, it absorbs moisture. Part-B component contaminated by moisture can cause issues with your manufacturing process.  Avoid exposure of the material to moisture in air. Keep the lid/cap closed air-tight when stored.


Purging the empty space in the container with dry nitrogen gas, argon gas, or negative-40-degree-due-point dry air is also recommended to prevent moisture contamination of part-B as well. (However, simply keeping the material in an airtight container may also be sufficient depending on the moisture level of the work place.) 


Store it in a dry indoor storage at a room temperature between 65 and 90 F. Avoid direct sunlight.


Part-B material contains chemical constituents that can separate during the storage.  Agitation of the part-B content before dispensing is recommended.  Separation can be seen in a higher degree when the material is stored in cold temperature. 




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 Safety Data Sheet (SDS) for detail information on safety and handling of the material.  The SDS for each component is sent with the shipment of the material. 


When 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, and if you expect the isocyanate content level in the work place atmosphere may become above the threshold regulated by OSHA or by other appropriate working place safety standard, we recommend, in addition to the above, installation of a proper hooded dynamic ventilation system and/or using an appropriate type of respirator (such as a full-face respirator equipped with OSHA approved HEPA filters for particulate and organic vapor) 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 and follow the other procedures by the Standard Industrial Hygiene Practices.  Please refer to the SDS for each component for the detailed health 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 near an ignition source.






For any questions, please contact Northstar Polymers.


Tel:         612-721-2911.

Fax:         612-721-1009

Web Site:    http://www.northstarpolymers.com

E-Mail:      info@northstarpolymers.com



Rev: May 9, 2016



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Northstar Polymers, LLC

3444 Dight Avenue South

Minneapolis, MN 55406

Tel: 612.721.2911

Fax: 612.721.1009

E-Mail: info@northstarpolymers.com


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.