Hand-mixable 6 Pound-per-cubic-foot Flexible Foam

6 Pound-per-cubic-foot

Hand-Mixable Flexible Foam

This foam formulation is designed to make cushioning products by either hand-mixing or machine casting. The components are liquid at room temperature. For a small quantity, this can be batched manually by hand tools. This can be open-cast into a slab or molded into a compression mold. The free-rise density of the foam is 6 pounds per cubic foot, and the cell structure is open-cell.

It uses MDI for the isocyanate component, which is generally considered safer than TDI. This formulation does not use auxiliary blowing agent such as Freon, HCFC, CFC, or flammable hydrocarbon materials. Only normal handling for industrial chemical is required.

Relatively safe and easy handling and the properties of this foam satisfy the requirements for the application as following and more:

Examples for Applications:

- Molded Upholstery Parts

- Custom Motor Cycle Seating

- Cushioning Parts for Sports Equipment

- Custom Packaging of Fragile Items

- Prototyping of Cushioning Parts

We recommend this formulation as a start-up formulation. We can modify this formulation to best fit your application.

Component Properties

Prepolymer (A) Curing Agent (B)

Code Number: MSA-018 PAN-020

Specific Gravity: 1.183 1.025

Equivalent Weight: 183 200

%NCO 23 % n/a

Mixing Ratio (A) (B)

Volume Ratio: 1.000 2.278

Weight Ratio: 1.000 1.973

Stoichiometry: 1.000 1.801

NCO Index 0.555 1.00

*Mixing ratio can vary within 5 %. Higher ratio of part-A will make the foam slightly harder, lower ratio of part-A will make it slightly softer.

Processing Temperature:

Part-A Ambient

Part-B Ambient

Mold/Substrate 100 - 110 ºF

* The ideal temperature for the mold and substrate is 100 - 110 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 110 ºF.

Cure Pattern:

Mixing time 30 seconds

Pot life (pour within) 1 minute

Demolding time 40 minutes

Complete Cure Cycle: 24 hours at room temperature

Recommended Processing:

I recommend testing small amounts to see how the material behaves, then develop your casting method accordingly. When you do test batch, 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 Material Safety Data Sheets for details on the safety and handling. The Material Safety Data Sheet will be sent with the materials.

Before you start your test, there is a chance the materials being frozen during the transportation in winter. This may cause separation within the components. If in such case, you need to agitate the components in the cans. Do not open the can for part-A (MSA-018) until you are ready to use as it is a moisture sensitive material. Heat the can to 140 - 160 ºF and shake the unopened can well to agitate. Do not use wooden paint stick as it has moisture within, which to contaminate the material. After agitating the components, keep them at a room temperature above 70 ºF. These materials should not freeze at room temperature. Be sure to cool the components to ambient before using, or other wise it will shorten the pot-life.

- Pre-heat the mold and substrate between 100 and 110 ºF.

- Apply mold release into the mold. Do not use silicone-base mold release as it destroys the foam surface. Use wax mold release or mold release products recommended for polyurethane foam by the manufacturer. Dry solvents in the mold release if any.

- Calculate the total inside volume of the mold (or the finished part volume) in cubic feet. Divide it by the density (6 in this case). This will give you the weight 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. Divide the weight by 2.975 to obtain the quantity of part-A by weight (in pounds). Multiply 1.975 to the weight of part-A to obtain the weight of part-B (in pounds). The mixing ratio can vary within 5% range. A larger ratio of part-B makes softer foam, and a smaller part-B ratio will make firmer foam.

- Take the correct ratio of part-A and part-B into a mixing cup. Mix very well with a steel or plastic stir stick for 20 to 30 seconds. Mixing is very impertinent for the good result. 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 you can mix well by hands. Employing a meter mixing/casting machine may be best for production quantity.

- Cast the mixture into the mold. The mold should be between 100 and 110 ºF. The material may not cure properly under this temperature. Heating too much also effect the foam quality. For a higher production rate, we can modify the formulation to cure faster.

- Cure in the mold for at least 40 minutes before demolding. Please check the strength of the foam surface before demolding. The surface may still be tacky at this point, but this is normal.

- Crush the foam with hands and pop the unopened cells in the foam. This will prevent shrinking of the foam by cooling. (In general, all flexible foams shrink slightly. Design your mold accordingly if tighter dimensions are required. )

- Store at room temperature for 24 hours to complete the cure cycle before evaluation.

Compression Molding

Polyurethane foam needs to fill the mold space by put slightly larger amount of foam material into the mold. The expansion pressure of the foam pushes the foam material to fill the mold space. The mold therefore needs to be a close-mold and has to have some capacity to retain the pressure. The simplest mold will be just an open-top box with a lid. The lid then needs to be clamped hold the pressure. The air trapped on the topside 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.

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 110 ºF in case of metal molds. If your mold is plastic or elastomeric mold, this may not be necessary as those materials absorb less heat than metal molds do.

Compression rate is the rate of how much more material you would put in to create the pressure. Typically, about 10 % compression should give enough pressure to distribute the foam within the mold. Using higher rate makes the foam denser and stronger.

Storage:

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 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.

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. The moisture contamination of part-B material is reversible. By heating material to 160 - 180 ºF and vacuuming it at about 29" Hg negative pressure for several hours will reduce the moisture level. 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.

Safety:

The 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.

When 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.

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.

Applications with fire-retardant grade

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 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.

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

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.