CompositesWorld’s first High-Performance Resins conference, held Sept. 23-24 in Schaumburg, Ill., offered ample proof that polymer scientists in this critical corner of the composites community are working hard to make these sometimes difficult-to-process materials easier to handle and more compatible with a wider range of applications.
The big topic early on was whether or not composites processors could ever expect to pay less than $75/lb (USD) for a high-performance resin. The answer, depending on the speaker, was yes and no. In any case, all other information shared during the two-day event proved that this corner of the composites community is working to make these sometimes difficult-to-process materials easier to handle and more compatible to a wider range of applications. The event focused primarily on thermosets, with some thermoplastics discussed, emphasizing preceramic polymers, polyimides, phenylethynyl imides (PETI), benzoxazines, phenolics, phthalonitriles, dicyclopentadienes (DCPD) and nano-based fillers and additives. Event chairs were David Leach, global product manager at Henkel Aerospace (Bay Point, Calif.) and Ali Yousefpour, from the Institute for Aerospace Research, National Research Council Canada. HPC was there and reported this synopsis of some of the presentations.
The conference began with a preconference seminar by Alexander Lukacs, director of technology at KiON Defense Technologies (Huntingdon Valley, Pa.), that shed light on preceramic polymers, polymers that convert to ceramic material upon heating to high temperatures (500°C/932°F to 1,400°C/2,552°F) via pyrolysis. They behave like organic polymers at low temperatures, and like ceramics once pyrolyzed. Lukacs focused on use of silicon-based polymers, including SiCN, SiC, Si3N4. The process involves traditional composites manufacturing with a polymer prepregged or infused into a fabric or unidirectional fiber. Following autoclave cure to shape, the part is pyrolyzed repeatedly (six to 10 times) to a ceramic of the desired density. Lukacs identified hot-section engine parts as potential applications for this material, including combustor, high- and low-pressure blades and vanes, turbine shrouds, flameholder, tailcone, and nozzles, flaps and seals. Brake rotors and exhaust system parts are also potential targets for this material.
James Sutter, a research chemist at the NASA Glenn Research Center (Cleveland, Ohio), began the conference with a big-picture review of high-performance resins challenges, history and future needs. The challenges, he noted, are substantial: sticker shock ($75/lb threshold mentioned above), complicated formulations, long-term monomer supply uncertainty, health hazards during processing, interfacial properties drop-off, limited manufacturing processes and large hot/wet knockdowns. Despite these, he noted, high-performance resins offer temperature and mechanical capabilities that are unmatched in other matrix systems. Future needs, according to Sutter, include: long-term use (>2,000 hours) at 300°C/572°F; compatibility with resin transfer molding (RTM), vacuum-assisted RTM (VARTM) and out-of-autoclave processing; hot/wet property knockdown of <25°C/77°F Tg; and lower cost.
Stewart Bain, president of BCI Inc. (Ottawa, Ontario, Canada), discussed PETI-330, being developed by UBE Industries (Tokyo, Japan). It’s a byproduct of Boeing/NASA resin research done in the 1980s and 1990s for engine and aircraft use. It resists micro-cracking, offers good open-hole compression data, is solvent-free and non-toxic, says Bain, and features a long shelf life. RTM and prepreg grades filled with IM7 and T800 carbon fiber are being developed and UBE is seeking collaborators willing to help the company test and evaluate large-scale production prepreg. And, noted Bain, “I don’t see anyone buying this material for $75/lb — or any material like it.”
Henkel’s Leach emphasized recent work done with that company’s Epsilon benzoxazine line, now available for use in RTM, VARTM, infusion, prepreg, automated fiber placement (AFP), tooling and adhesive film applications. It features good fire, smoke and toxicity (FST) performance and a hot/wet Tg range of 147°C/297°F to 161°C/322°F, depending on grade. Epsilon with glass and carbon fiber from Toho Tenax (Rockwood, Tenn.) was used most recently in the auxiliary power unit and duct in the Airbus A380 tail section, a part that won an Innovation Award at the JEC Composites show in April. Leach said Henkel is evaluating blends of benzoxazine with epoxies and other resins.
Aircraft interiors was the focus of the next presentation. Carl Varnerin from Lewcott Corp. (Millbury, Mass.) emphasized next-generation snap-curing phenolic prepregs. Varnerin noted that phenolics are notoriously brittle and difficult to self-adhesive to aramid honeycomb. To address this, Lewcott developed LC196, an E-glass prepreg with flex strength of 620 MPa, flex modulus of 22 GPa, tensile strength of 503 MPa, tensile modulus of 23.4 MPa and the ability to self-adhere to aramid honeycomb core — climbing drum peel is 53-71 Nm/m. Varnerin said cure time of the material is 17 minutes and peak heat release in fire tests is 39 kW/m².
Mike Favaloro, technical marketing, Fortron PPS Composites at Ticona (Amesbury, Mass.), focused on a thermoplastic. Fortron is a linear polyphenylene sulfide (PPS) that Ticona is positioning to displace thermosets in aerospace applications. This semicrystalline material is inherently flame resistant, resists chemicals, is injection moldable and extrudable, and offers a moisture absorption rate of just 0.02 percent. Favaloro reported on the material’s successful use in the manufacture of a carbon fiber/PPS seat frame manufactured by CDI (Avon, Ohio). More recently, Fortron was used by Fokker Aerostructures to mold the tail section of the Gulfstream G650 business jet, representing the first welded thermoplastic composite aircraft primary structure in series production.
Raising a few eyebrows at the conference was Darren Boyce, owner and operator of Boyce Components LLC (Phoenix, Ariz.), who introduced a heatable resin system for out-of-autoclave tooling and heated composite applications. The system consists of a layer of fiberglass composite overlaid with expanded metal foil conductors and bus bars embedded in resin and fed by a 120V or 240V wall current. Sprayed or brushed over this is a thermosetting resin that features carbon nanotubes (CNTs) in 3 percent concentration that provide conductivity for the current in the foils beneath. For tooling, this material can provide general warming for tape or prepreg placement, maintain mold at set temperature, or cure composite laminates on the tool surface. For composite parts, Boyce said the technology can provide heat in panels and tubes as well as de-icing and anti-icing functions. The latter, said Boyce, is being evaluated for use in wind blade applications.
Vince D’Arienzo, technical fellow at Bell Helicopter Textron Canada Ltd. (Mirabel, Quebec, Canada), delineated his company’s composites goals and aspirations in helicopter design. Bell, he said, is focused very much on overall part cost, including tooling, layup and cure time. It’s looking for material and process solutions that minimize process cost. In the process, Bell is moving away from sheet metal and toward composites, consolidating parts in the process. That said, there are concerns, D’Arienzo noted. First is lightning strike and electrical current management. Right now, Bell must add weight in the form of copper mesh or similar technology to manage lightning strikes. The company is looking to CNTs to help it solve this problem. Also a challenge is detection of non-visible damage in composite structures, he said. Ultimately, he said, Bell is “looking at the business side of operations. Consolidation of parts may create a composite process that takes longer, but reduction of complexity is paramount — fewer drawings, fewer parts, fewer opportunities for errors.”
Brian Edgecombe, director — materials research and development at Materia Inc. (Pasadena, Calif.), brought conference attendees up to date on his company’s efforts to develop a monomer-based, catalyst-enabled pDCPD (polymerized dicyclopentadiene). Tests of the material, noted Edgecombe, indicate that this thermoset enhances fiberglass fatigue properties and thus could be a good fit in wind blade applications. It’s compatible with VARTM, offers “water-like” viscosity, and cures at 120°C/248°F, he reported. This temperature is substantially higher than that required by current wind blade resins, but within the capabilities of most wind blade manufacturers, Edgecombe said. Other benefits of the material include low-density, high Tg, water resistance and slow, short crack growth. Materia is working with Montana State University to test the material, evaluating carbon fiber-based laminates (50k to 60k) and trialing the pDCPD with several blademakers. Also, look for a tradename for Materia’s pDCPD sometime soon.
Michael Connelly, product manager at Huntsman Polyurethanes (Auburn Hills, Mich.) used the conference to introduce Vitrox, a new long pot-life polyurethane for automotive applications. Designed for infusion, RTM, VARTM and filament winding applications, Vitrox has a gel time of several hours (adjustable down to a few minutes), provides low viscosity until snap cure, offers a Tg of more than 200°C/392°F and reportedly has good mechanicals and inherent FST performance.
Tim Spahr, regional business manager at Oxford Performance Materials (Enfield, Conn.) reviewed performance properties and process capabilities of OXPEKK, a polyetherketoneketone (PEKK)-based thermoplastic for aerospace, oil and gas and electronics applications. A semicrystalline, it’s designed to bridge the amorphous/crystalline polymer gap, it offers strong fire performance, low moisture uptake, low dielectric constant, high dielectric resistance, Tg of 155°C to 163°C (311°F to 326°F) and good mechanicals. For composites applications, OXPEKK is available in carbon fiber tape or prepreg form. Process options include autoclaving, compression molding, Relay system molding (Fiberforge), and automated tape laying (ATL). Bonding options include ultrasonic welding, spin welding, inductive welding and laser welding.
CompositesWorld’s next conference is High-Performance Fibers 2010, Nov. 9-10 in Charleston, S.C. For information on this and other CompositesWorld conferences, visit www.compositesworld.com/conferences.