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Shock-Absorbing Plastic Foam.--A new shock-absorbing plastic foam that is more adoptable for packaging beause it is not "sticky" has been developed for the Air Force. The addition of a fatty acid such as stearic acid, to common foam plastics by Air Research and Development Command scientists eliminated the "stickiness" and produced a more resilient material of variable density.
Known as polyurethane foaming, the process is used to protect equipment during shipping by bedding it in a high-strength, lightweight foamed plastic. The thick protective cushion is either molded individually as a container, or foamed into the container holding the item to be shipped.
Two chemicals, polyester or polyether resin and isocyanate, are poured into the mold or container with an amine catalyst. A chemical reaction takes place releasing carbon dioxide in a thick foam which hardens in a few seconds.
Formerly, it was necessary to wrap equipment in polyethylene or waxed paper to prevent foam from "sticking" to its surface. Molds also required waxing after each molding operation.
The improved plastic using the additive does not adhere to bare metal or glass surfaces.
Use of the additive has also improved static load carrying properties. Under seven-tenths pounds per square inch pressure, foamed plastic cushions, without the additive, showed 80 per cent strain. With the additive, the same pressure revealed only 18 per cent strain. Density of the material may be controlled by varying the quantity of fatty acids.
Scientists from ARDC's Wright Air Development Center, Dayton, Ohio, developed the new polyurethane foaming process with additive in the Protective Processes Materials Laboratory.
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