First-generation, simple bisphenol-based phthalonitriles had high melting points and a short processing window. The Navy scientists addressed these issues in the new second-generation, oligomeric PEEK-like phthalonitrile. With no curing additive present, the resin or composite starts to soften and melt at about 60°C to 63°C. At 125°C, 150°C, 175°C, and 250°C, viscosity values were 1,940, 230, 80, and 30 centipoise (cP), Keller told us.
Although the curing temperature of both first- and second-generation phthalonitrile is the same, newer curing additives afford the ability to cure above 150°C, with faster curing reactions at higher temperatures. This makes it easily possible to control the time to cure and the speed at which the polymerization reaction occurs as functions of the amount of curing additive used and the curing temperature.
"The new phthalonitrile resin can be cured to a shaped solid or gelation at 200°C or 250°C, with curing occurring faster at the higher temperature," said Keller. "With some catalysts or curing additives that we've especially developed for the PEEK-like phthalonitrile, we can even cure to gelation at temperatures as low as 150°C. Of course, the shaped, cured component can be post-cured at higher temperatures to complete the cure, and the postcure can be done on the cured shaped polymer or composite in a high-temperature oven and in the absence of an autoclave or pressure."
Keller said the fact that the material does not soften or exhibit a glass-transition temperature at temperatures over 400°C during continuous modulus mechanical studies is novel. "Other polymers have not previously been reported with this characteristic and with the ability to retain shape under stress at temperatures up to 350°C for aerospace, oil drilling, and other domestic applications needing such stability. Moreover, the cured phthalonitrile is oxidatively stable for applications at these temperatures."
Aside from applications for oil rigs, aircraft, and ships, others may include robotic and autonomous firefighting systems, fire-resistant textiles, automotive components, wind turbine blades, structural composites, and battery casings.
Rob, I discovered the US Navy's research when I was looking into "nautical" robots. One of the robotic jellyfish we wrote about, RoboJelly, as well as its big brother Cyrus, are projects funded by the Office of Naval Research. The NRL is only one entity involved in various types of research, and it also serves the Marines.
Ann-very informative article. Kudos to your level of intellect and experience in this very technical arena of advanced material sciences. I knew that you were a materials person, but you've just raised your own bar! You've delved into materials processing topics I have absolutely zero knowledge of, including resin infusion molding (RIM) and resin transfer molding (RTM).
Regarding the physical properties descriptions of this stuff --- (Phthalonitrile – did I pronounce that correctly-? ) --- thermal and water-absorption resistance, coupled with its strength are impressive. Thanks for opening this door for me; looking forward to learning more.
Wow, thanks, Jim. I wasn't sure if readers wanted something this technical, but many discussions like this one just don't reduce down. RTM and RIM are standard processes that have been around awhile but not for high-performance materials like this one.
ON the issue of technical writing, DN has consistently evidenced that the deeper a technical issue is, the lesser the comments. (Case in point; this article). But I think that should be expected; -- for example, there have been several other deep articles from Guest Bloggers that I couldn't begin to comment on. The interested field of commenters just naturally narrows.
ON the subject of RIM, I was [minimally] familiar with another industrial process – Reaction Injection Molding (a different RIM) which is [loosely translated as] an injection of a 2-part epoxy. A very slow processing time because 'cure' is required. Checking my old faithful resource, Wikipedia doesn't have a page for your definition of RIM but does link it to your other suggested process, Resin Transfer (RTM).
Always interesting to learn about new things – Thanks!
Ann, while I don't have a use for this information today, it is certainly handy to have. This source of knowledge is a resource, and like most resources becomes reallyn valuable wnen you need it, and only "interesting" the rest of the time. I can see an immediate application of this material in high frequency hiher power RF electrical applications.
What was not mentioned about the new material was outgassing, which affects the usefulness of a material for satellite and space applications, and also for semiconductor fabrication applications.
The Navy's new powerful LaWS laser weapon is great at taking out composite targets over a mile away. How much time before other countries like China and Russia design their own and burn through our composites?
More and more robots are becoming more autonomous all the time. Now Lockheed Martin has completed a demo mission with two completely autonomous robotic vehicles performing resupply, reconnaissance, surveillance, and target acquisition.
Producing high-quality end-production metal parts with additive manufacturing for applications like aerospace and medical requires very tightly controlled processes and materials. New standards and guidelines for machines and processes, materials, and printed parts are underway from bodies such as ASTM International.
Although plastics make up only about 11% of all US municipal solid waste, many are actually more energy-dense than coal. Converting these non-recycled plastics into energy with existing technologies could reduce US coal consumption, as well as boost domestic energy reserves, says a new study.
This year's Dupont-sponsored WardsAuto survey of automotive designers and other engineers shows lightweighting dominates the discussion. But which materials will help them meet the 2025 CAFE standards are not entirely clear.
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