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October 1, 2004

3 Min Read
Tough foam offers composite tooling alternative

A structural support foam developed by researchers at the U.S. Dept. of Energy for in-house use is now being marketed for composites tooling, as well as other applications.

Amodified polyisocyanurate called Tepic is expected to make a big impact on the $100-million/yr global composite tooling market, according to researchers at Sandia National Laboratories (www.sandia.gov) in Albuquerque, NM, part of the U.S. Dept. of Energy (DOE). It could see use in prototype or production-run composites tooling or in prototype injection molds. Scott Vaupen, a business development associate at Sandia, says additional applications may include tooling for hot embossing, as a high-temperature adhesive, or as a core material in structural applications.

The laboratories are operated by Sandia Corp., a Lockheed Martin company, for the DOE''s National Nuclear Security Administration. LeRoy Whinnery, one of the lead researchers on the material, explains that the Tepic name no longer stands for anything. "Several years ago the material was misnamed and an acronym established. The name stuck and I decided that it would be less confusing to keep it than change it," he says. The development came about as Sandia discovered the need for a high-temperature-resistant foam for a structural application. The foam''s density initially was about .4 g/cu cm, but now a range of densities from .2 to .8 g/cu cm are offered, he says.

A closer look

Polyisocyanurates are very similar to polyurethanes, and some are already used to make insulating foam. The chemicals used to make Tepic are liquid when first mixed together and can be poured into a mold, around a part, or into billet form. The material cures exothermically into a rigid foam. "At this point the part can be removed from the mold for post-cure at approximately 50 deg C above the expected use temperature," Whinnery explains.

Standard composite tooling board materials are made of many different materials depending on application and curing temperature, but thin slabstock epoxy and polyurethane tooling boards are common. To form thick molds, multiple boards must be bonded together; these laminated structures can separate after only a few cycles. Tepic, however, can be poured into a mold or machined from much thicker cast billets, eliminating the need to bond and repair large tools. It retains strength to temperatures in autoclave processing in excess of 205ºC at 7 bar.

While Tepic is expected to be cost-competitive with existing tooling boards, it can be used to process higher-temperature-curing composites (>175ºC). It can be used with many standard mold releases and gel coats for multiple parts removal and for surface finish requirements, says Sandia. It is also repairable using commercial adhesives.

Tepic compares favorably against metallic composite tooling as well. It is significantly less expensive than bulk aluminum, according to Sandia, and one-fourth the density. Weight and cost savings are even greater in comparison to more specialized alloys.

Vaupen says Sandia has signed a short-term (about one year), non-exclusive license with one company and is completing a long-term exclusive license for Tepic''s use as composite tooling with another company. These licensees will determine if Tepic will be available as a pourable kit or solely as a billet or board. Sandia will not reveal either firm''s name until long-term licenses are signed. The foam is still available for use in other applications, and more than 30 companies have so far expressed interest for applications beyond composites tooling, says Vaupen.

Matthew Defosse [email protected]

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