++++ Test Instructions
Testing Instructions
for Rigid Closed-Cell Foams
This is generic information for our typical polyurethane rigid closed-cell foam materials. This document does not contain the mixing ratio or other specifics of the particular materials you may be using. Please see the separate information provided by Northstar Polymers for details on the specific formulation.
Personal Protection
Please be sure to operate in a well-ventilated area. Wear rubber gloves, long sleeve shirt, and protective glasses. An eye bath or a washing facility should be near by and readily available in case of skin/eye contact of the material. Please refer to the detail safety information in the enclosed Material Safety Data Sheet.
Component Materials
The components should be kept at the room temperature at least 24 hours before the testing. The mold should also be at the room temperature. If you are using compression mold for production of molded parts, you may heat it about to about 100 ºF.
Tools
1. Mixing Container
The mixing container can be 5 gallon pail, 1 gallon paint can, or any container that has round side and flat bottom. The material sticks to the inside surface and it is hard to get it off. The container needs to be disposable.
2. Stir Stick
Paint stick can be used as a disposable mixing stick. Stainless steel spatula can be used for multiple use. For larger batch, paint mixing or mortar mixer head with power mixing tool (or speed variable hand drill) can be used together with a stir stick.
3. Paper Towels
Paper towels can be used for cleaning. After cleaning, dispose the paper towels as an industrial solid disposal. Isopropanol alcohol can be used to aid cleaning. Other solvents such as MEK or Acetone can also be used to aid cleaning, but isopropanol is safer and easier to obtain. Those solvents are often flammable. Please follow the solvent instruction for safety and handling of the solvent.
4. Measuring Cups/Scales
You need to measure a correct ratio. Please refer to the separate information provided by Northstar Polymers for the correct ratio. The components in the test kit may not be pre-weighed. Please do not assume the components are packaged at the correct ratio.
You can use measuring cups or any disposable cup for measuring the components. A scale can also be used for measuring. Please note the volume ratio and weight ratio are different as the densities of the components differ. The correct mixing ratio is crucial to the outcome of the foam. Please try to be as accurate as possible. The provided volume ratio is correct at 77 ºF. If you have a problem may be caused by an incorrect mixing ratio, try using weight ratio instead of volume ratio.
(Even if the ratios are slightly off (within about 3% to 5%), it still makes foam in general. If you batch at a slight off-ratio, the foam quality may be slightly different. You can develop your own mixing ratio range specification based on how much specification tolerance your application can take.)
5. Mold or Frame
These foams can be cast in a closed mold or open mold. The mold can be made of various materials that have a non-porous, clean, and dry surface. If you are using wood or some other porous material, the surface needs to be coated with a sealer (gel coat, acrylic, epoxy, or other plastic coating) for a smooth surface. If you are using a compression mold, the mold needs to have a lid made of a very sturdy material. If you are using steel, aluminum, or other materials, you may need to heat the frame or mold to about 100 ºF as they absorb heat energy that polyurethane foam requires for curing reactions.
6. Mold release
These foams are very sticky when poured into a mold. If you need to demold the foam, you need to apply a mold release. Wax mold release is commonly used in foam making. They come in a few different types including sprayable and brushable. They are available through your local industrial supply distributors. Please specify wax mold release for polyurethane foams when you purchase. Sprayable is easy to use. If your supplier do not carry such, you can call 800-323-6433 Slide Product. We use either "Thermoset Release" product number 45416T, or "Urethane Mold Release" product number 45812N depending on your application requirements.
Water based mold release is not recommended. Also, some hydrocarbon based release agents effect the quality of the foam. Silicone mold release destroys the surface of foam. Please note that the choice of mold release is very important when you need a good finishing surface.
If you are filling a shell and do not have to demold, you do not need mold release.
7. Nitrogen gas
For storage (see the end of this document for the supplier
information)
Procedure
1. Prepare the test mold or frame.
2. Apply mold release, if needed. Wait until the solvent within the mold release dries.
3. Measure the inside volume of the frame or mold. If you obtain the inside volume in cubic feet, multiply by the density. This will be the approximate weight in pound of material (shot size) you need. Make a little more than precisely what you need. Calculate required amount of components according to your ratio specification. When you are using a compression mold, adjust the amount for your desired compression rate.
4. Weigh and pour part-A material into the mixing container, and add the correct amount of part-B. The pouring order of A and B is not important, but the mixing ratio is important. Throughout the test, we recommend recording actual weights of the components at each batch for your reference.
5. Agitate the mixture vigorously and homogeneously, scrape bottom and side as you mix. For polyurethane foams, generally you have less-than-one-minute pot life. The typical cream-time for these materials is about one minute. The material starts to become thick and worm. It creates internal heat when mixed. More the volume (amount), hotter the material gets. Hotter the material gets, faster it cures, so you may have a shorter pot life when you are mixing a larger batch.
Foam formulations require certain "speed" for foaming. Pour the material quickly to the mold while it still flows. Two to three minutes from the beginning of agitation may already be too late if you are pouring a large amount.
The free rise density may vary depending on how much air you enclose when you mix. Compression molding method can control the foam density.
Even if you are not making compression molded parts, it is a good idea to make an enclosed frame or mold for the part, so that you can use rising pressure of the foam to push itself to the corners of the frame. In this way, you can distribute the foam within the frame or mold without having to be liquid.
6. The foam slowly rises to the final volume over about 3 to 20 minutes (it varies depending on the formulation). Cure the foam for the time specified in the data sheet. Although it becomes solid within one our, the foam often needs about 12 to 24 hours to have its final physical properties.
7. Demold the foam carefully, if needed. If there is not enough mold release or using incorrect type mold release, you may encounter difficulty. Build-up from mold release could also cause difficulty when demolding. If you see distortions on the surface, clean the mold with a solvent, then apply mold release. Wax mold release works better at a certain temperature range. Often wax release works better when the mold temperature is between 90 to 120 ºF. If it is lower, it is too stiff, so it bonds to the mold surface. If it is too high, it is more liquid so it looses the effect of the release.
Physical Testing
Although the foam can be handled as a solid part within one hour, the foam continues to cure to the final properties over a couple of days. If you are conducting the mechanical strength of the foam, please do so at least 1 to 2 days after mixing.
Post-curing at 140 to 180 ºF may speed up the cure. Refer to the data sheet for the specific formulation.
Storage
Shut the lid tightly and store in a room temperature or temperature controlled storage above 72 ºF. Shelf life of the material is expected to be 6 to 12 months under correct storage condition. Part-A material contains moisture sensitive material. Whenever open the lid, blanket the space above the material with nitrogen gas before storing part-A.
Nitrogen gas can be obtained through Praxair, 800-772-9247.
Cold weather could effect the material. When the material is in an extreme low temperature, the contents of the component may freeze out and separate from the other contents. In that case, heat the material to 100 ºF and agitate the component before mixing to ensure homogeneous mix of the frozen out content.
Cleaning
Use paper towels to wipe the tools. Isopropanol alcohol can be used to aid cleaning. MEK or DBE can also be used. Be aware of the flammability and other hazardous issues of those solvents. Consult your supplier for the handling information on solvents.
Disposal
Do not dispose of the material into public drain or any unlawful area. The mixed and cured material generally can be disposed of as an industrial solid waste. Try to dispose it as solid. Consult your local authority for the rules. Please refer to the Material Data Sheet for detail information.
Additional Safety information
The part-A material contains a type of isocyanate: MDI. A small number of people who were in contact with an isocyanate material could develop hypersensitivity to isocyanate. A person with the isocyanate sensitivity may react to part-A component severely, even though the level of vaporized isocyanate is under the threshold limit value of 0.02 ppm. The symptoms include irritation of eyes and asthma-like respiratory tract. If one with the isocyanate sensitivity needs to work with the material, extra protection such as half-faced respirator together with protective clothing, protective goggles, as well as the rubber gloves.
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 foam 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 for the conformance to the applicable regulations when needed.
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Rigid Closed-Cell Foam Index Page
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.