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| Frequently Asked Questions |
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What are the benefits of common specifications? |
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A single universal specification allows foams from various sources to be compared easily/rapidly for compliance. It also allows foam manufacturers to 'tune' their production lines to meet one set of functional properties rather than a plethora of potentially conflicting specification requirements. |
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Was there unanimity in the selection of the properties selected for inclusion in the Molded Polyurethane Foam Industry Panel specification? |
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Yes, all members polled the experts in their respective organizations and the properties appearing in the specification were unanimously selected by all of the companies represented on the Panel |
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What are the most important properties to measure for foam performance? |
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The foam properties included in the Molded Polyurethane Foam Industry Panel specification have been carefully selected and thoroughly checked to prove their worth (repeatability/reproducibility).They are considered to be the most important properties to measure the actual functionality of a foam product. Other properties have been omitted since they do not predict how a foam will perform in it's intended application. |
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How have the functional foam properties been checked? |
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All of the Molded Polyurethane Foam Industry Panel specification properties have been subjected to Inter Laboratory Studies (ILS), also known as Round Robin testing between a number of ISO 17025 accredited labs. The data from these labs. has been processed using the methodology in an ASTM International standard (E691) to ensure that the data is repeatable and reproducible. |
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Chrysler has adopted the Industry Panel specification and GM and Ford have included many of the recommendations in their seat foam specifications. What about the rest of the Automotive OEM's? |
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We are hoping the content of this site, communication, and sharing of seat / foam functionality data will in time convince all OEM’s to recognize the benefit of a common specification and acceptance of the Molded Polyurethane Foam Industry Panel specification will eventually become universal. |
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Should material tests for automotive seat cushioning vary based on the type of material utilized, if the application is the same? |
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It is the Industry Panel’s opinion that seat cushioning material, regardless of type, should meet the same requirements, since the end function and performance requirements of the material are the same. All cushioning materials must allow seating to perform well during the vehicle lifetime, including flammability requirements. |
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Are there other cushioning materials, besides polyurethane foam, used in automotive seating? |
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A good question! Very little non-foam cushioning materials are used worldwide. Alternative cushioning materials, like latex foam or coconut fiber pads, usually have carry-over or obsolete property requirements based on material characteristics, not product function. These materials typically have a negative economic or performance impact on the finished seat. |
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Why must foam be tested using standard Temperature and Relative Humidity (RH) conditions? |
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Foam properties are altered by changes in environmental test conditions. For instance, an increase in % RH decreases foam hardness. Thus foams are conditioned and tested in a controlled laboratory usually at 23 + 2?C and 50 + 5% RH. Therefore properties can be compared from lab-to-lab. |
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What is the difference between ILD and IFD? |
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These terms express the relative hardness of foams. The obsolete term ILD meaning Indentation Load Deflection is a misnomer inherited from the latex rubber foam industry. The correct term is IFD where F = Force since hardness is determined by applying a force to a piece of foam at a specified deflection ,e.g. 25/40/50/65%. |
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Does foam change over time? |
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The long term performance of flexible polyurethane foam has been proven via accelerated laboratory testing and long term actual use observations. The properties of a quality flexible polyurethane cushioning foam remain essentially unchanged during the lifetime of a vehicle. |
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Does the Constant Force Pounding test truly predict the long term performance of flexible cushioning? |
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A pounding or a dynamic fatigue test performed under standard test methodology and test conditions will indicate the relative performance of a foam material over a long period of use. The major benefit of an accelerated durability test is to ensure that performance of a specified foam performs well in its targeted seating application. |
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What is the difference between TDI and MDI foam? |
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These acronyms stand for Toluene Diisocyanate (TDI) and Methylene Diphenyl Diisocyanate (MDI). They are different types of isocyanates made via differing chemical starters and production techniques. Both have isocyanate reactive sites that will react with the polyol and other ingredients to produce polyurethane products, e.g. foams, elastomers. Either can be used to produce quality automotive seat cushions. |
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What is the definition of renewable [Bio- / Soy-] foam? |
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Renewable Polyurethane foam usually implies that it contains a portion of ingredients made from non-petroleum resources such as vegetable oils. |
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Is molded polyurethane foam recyclable? |
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Yes! Foam is reusable/recyclable either physically, such as the ground up foam used in carpet underlayment. (e.g. rebonded product) or broken down chemically using chemolysis. This process is called glycolysis. The glycolysate product can be used to make new products. |
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Do foam hardness and density have a direct relationship? |
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They are linked together, but foam hardness and density can be independently varied. For instance high density foam may be made luxuriously soft whereas a low density foam can be made stiff and hard or vice-versa. Many intermediate hardness and density combinations are possible. This allows a foam manufacturer to target durability and comfort parameters within a vehicle to address performance expectations based on seating position and occupant usage level. |
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Where do I get OEM and Industry engineering specifications? |
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The most recent releases of seating foam specification for Chrysler, Ford and General Motors products can be purchased on line from independent document services. (See our Links section for sources). Most of the other OEMs have to be contacted directly or via a Tier 1 supplier to source their specifications. |
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Why do foams discolor, and are there any changes in properties? |
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Foams made with aromatic isocyanates such as TDI or MDI will turn shades of yellow upon aging with exposure to light. The discoloration is due to UV light exposure, which causes the aromatic bonds to sever and color species to be formed. The extent of discoloration is usually only a few millimeters deep and the properties of the foam do not change, i.e. neither physical property or flammability performance are altered due to the color changes. Since most foams are covered in use, this discoloration is not considered to be a problem unless very light, thin coverstock is used. Light protection agents are always added to foam formulations to minimize discoloration during foam storage. Occasionally color pigments can be added to mask discoloration. |
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How does core density relate to a final molded part weight and the achievement of the required hardness specification? |
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Core density for a molded polyurethane foam system is typically stated for simple test block molds at a standard just fill weight and standard hardness for the particular system.
An actual molded automotive seat being more complex than a test block mold requires at a minimum 10% or higher core density just to fill the part. Core density times the mold seat volume times a 1.1 factor is a good starting predictor of a system to part mass requirement. However, there are many other design parameters that might require the use of a higher factor. (See the next question for further explanation). |
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What design parameters determine the final molded part weight requirement for a given foam chemical system and why is it so difficult to predict? |
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Many factors go into the final mass part requirement for a molded foam part and there are no simple straightforward predictions, due to the contributions of part geometry, system process ability, and system chemical design:
- A given chemical foam system will have a defined potential for blow or free rise density and this determines the degree of over pack for the molded system.
The final molded part density divided by the free rise density determines the over-pack factor required to make a void and defect free molded part. Over-pack factors of 1.05 to 1.75 are common respectively for simple to more complex geometry molded tools.
- The hardness potential for a chemical system is typically designed by the supplier to cover a range of hardness versus final molded density. A softer base hardness designed system will require more over pack and thus more weight to achieve the given hardness requirement than a harder base designed system.
- Foam hardness is a function of the square of the density, so small changes in part weight or final molded density are often necessary to achieve the hardness specification requirement.
- Foam hardness is also a function of the part thickness, so a higher hardness foam system and/or a higher molded density part is necessary, if one wishes to design a thinner part achieving the same hardness or support.
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