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SAN ANTONIO — Baby bottle nipples and air-bag covers may be miles apart in the consumer mind, but they each offer a new field for the use of thermoplastic elastomers, according to speakers at Flexpo 97 in San Antonio.

Several medical products, such as bottle nipples, needle shields and intravenous equipment, now are being made from TPEs instead of PVC, according to Scott Young, market development manager for West Co., a Lionville, Pa.-based firm.

``A lot of producers don't want to get into PVC because of the incineration factor, particularly in Europe'' said Young, whose company rang up $458.8 million in sales of pharmaceutical closures in 1996. ``Five years ago, these products weren't being made from TPEs.''

Young added that TPEs may have a future in replacing other natural rubber products that have dominated selected medical markets, because of the number of pediatric, geriatric and AIDS patients who are allergic to the natural rubber proteins in latex.

Bottle nipples were the first medical products West made from TPEs, which repeatedly can be stretched to at least twice their initial lengths with full, rapid recovery. In the nipples, TPEs showed excellent pull strength, and good long-term aging and radiation-stable properties.

Medical products using TPEs are less expensive than silicone, but still cost 21/2 to three times as much as products made from medical-grade PVC. That cost factor represents the major drawback TPE manufacturers have to correct to establish themselves in the marketplace.

Timothy Whited, project engineer at Autoliv Inc.'s engineering center in Rochester Hills, Mich., was another man in search of a new material at Flexpo. Whited needs a product that will stand up to the explosive, 10-millisecond period when an air bag inflates during a collision.

AutoLiv, a London-based firm with more than 30 percent of the global automotive safety market, uses polyolefins, TPEs and other materials, depending on the make and manufacturer of the vehicle. Polyurethane, the previous material of choice for air-bag covers, largely has been phased out because of higher costs, he said.

``We're trying to commonize our designs in order to commonize our materials,'' he said. ``Using multiple designs and multiple materials is a lot of work. Right now, it's hunt and peck.''

Prospective materials must pass a gamut of harsh testing. One AutoLiv customer requires the air bag and cover to function properly after 21 days at temperature extremes.The cover seams in the material must split to allow the air bag to escape, but the material also must be strong enough so that the air bag does not become a projectile.

The firm is moving toward a styrene ethylene butadiene styrene compound, but is open to new elastomers, Whited said.

``There are quite a few different animals you need to defeat to get an air bag into production,'' he said.