GE ExtemPlastic Takes The Heat

GE Plastics has upped the ante on the temperature performance of its plastics portfolio with the development of a new family of amorphous thermoplastic polyimides. Some of these Extem polymers retain their stiffness at continuous use temperatures as high as 230C, according to Rob Costella, the company's global product manager for high performance polymers.

Extem's closest cousin, GE's Ultem polyetherimide, has continuous use temperatures that top out at about 180C. And temperature isn't the only thing Extem has going for it. Compared to Ultem and other types of amorphous thermoplastics, Extem exhibits improved resistance to chemicals - including normally troublesome chlorinated solvents and basic environments.

Extem also promises flame resistance without the use of halogenated stabilizers. Flammability testing is still taking place, but Costella predicts Extem will offer very similar UL94 performance to Ultem, which is well-known for its ability to withstand fire. "Like Ultem, Extem is inherently flame retardant," says Costella.

And like Ultem, Extem can be melt processed via injection molding, extrusion and blow molding. One key feature is that Extem develops its maximum mechanical properties right out of the mold. "We've eliminated the post-mold curing step required by some other imidized materials," says Brian Herington, GE's general manager for high-performance polymers.

The added temperature performance, chemical resistance, and efficient melt processability makes Extem a candidate for a variety applications that currently use semi-crystalline polymers, thermoset polyimides, or other "imidized" materials such as polyamidimide. These include electrical parts such as connectors or even flexible circuits. "Extem is compatible with lead-free soldering," Costella notes. Other likely applications include under-hood automotive parts, bearings and gears, semiconductor wafer handlers and components for down-hole oil and gas drilling.

GE has been working on Extem for the past 14 years, developing patented catalyst and monomer chemistries. "It's really a whole new family of polymers," Herington, who explains that Extem is based on proprietary amines and anydrides.

GE will initially commercialize two types of Extem resins, each with a different balance of properties: Extem UH, which has a glass transition temperature (Tg) of 311C, will offer the best elevated temperature performance as well as the best chemical resistance. Extem XH offers a Tg of 267C but better flow and creep resistance. Both types of Extem will eventually be available in glass- and mineral-reinforced versions as well. Over time, GE plans to expand Extem to more than 75 different grades, reports Herington. Some of these will be specialty materials, such as ESD grades, created by GE's LNP division.

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