Toho Tenax Develops 'Super-Heat-Resistant' Prepreg for Engine Apps

February 1, 2015

Ryan Gehm

Toho Tenax Co., Ltd. announced Nov. 6 that it has developed a new prepreg — a carbon-fiber sheet pre-impregnated with matrix resin — that offers super-high-heat and -oxidation resistance suited to aircraft and automotive engine compartments.

Toho Tenax’s new bismaleimide resin-impregnated prepreg does not reach glass-transition below 320°C (610°F). Production applications are currently in progress in the aerospace industry.

The new bismaleimide resin-impregnated prepreg does not reach glass-transition below 320°C (608°F), the result of Toho Tenax’s original resin-formulation technology. Transition temperatures around 200°C (392°F) are typical of other prepegs, according to a company spokesperson. The supplier declined to provide any more details on the resin composition and its development program due to non-disclosure agreements (NDAs).

The new prepeg also maintains oxidation resistance without heat cracks under continuous use in the upper 200°C (lower to mid 500°F) range. This capability is what makes the technology unique, the spokesperson said.

Conventional bismaleimide resin-impregnated prepreg already has been used for high-temperature applications such as automotive and motorbike engine compartments, but it has experienced degradation, according to Toho Tenax, due to resin oxidation after continuous use at high temperatures. For example, microcracks can form after repeated heat expansion and contraction.

The super-heat-resistant prepeg cures at 180°C (360°F) for 2 h in the mold, then at 210°C (410°F)/9 h, 250°C (480°F)/10 h, and 270°C (520°F)/10 h without the mold for post-cure. The production volume/limit for this new prepeg has not been fixed, the spokesperson said.

Production applications are currently in progress in the aerospace industry, but again details could not be provided due to NDAs with clients.

Aerospace has been a traditional focus area for Toho Tenax, but the Japanese materials supplier is now expanding the scope of its technology development to include other high-heat applications such as ground vehicles. For example, the company announced Nov. 5 another prepeg development—this one initially targeted for automotive applications and focused on rapid curing for increased productivity.

The new prepreg, which is said to feature excellent surface texture and formability, cures in 3 min at 150°C (300°F) and minimizes resin being expelled from the prepreg due to molding pressure. The result is an increase in production efficiency “by a factor of many dozens,” according to Toho Tenax, which will allow the company to raise annual production capacity to 50,000 carbon-fiber-reinforced plastic (CFRP) sets.

Toho Tenax plans to explore opportunities for aircraft and other fields, including sports equipment, with this new prepeg due to its formability at low pressure of around 0.5 MPa (70 psi). A flame-resistant feature now under development is expected to further expand applications to consumer electronics and other general applications.

The materials supplier also intends to develop CFRP technologies for structural parts. “Material development for first and second structural members of aircrafts and frame of automobiles are in progress,” the spokesperson shared.

Toho Tenax is the core company of the Teijin Group’s carbon fibers and composites business.