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?
As the 3D printing and overall additive manufacturing ecosystem grows, standards and guidelines from standards bodies and government organizations are increasing. Multiple players with multiple needs are also driving the role of 3DP and AM as enabling technologies for distributed manufacturing.
A growing though not-so-obvious role for 3D printing, 4D printing, and overall additive manufacturing is their use in fabricating new materials and enabling new or improved manufacturing and assembly processes. Individual engineers, OEMs, university labs, and others are reinventing the technology to suit their own needs.
For vehicles to meet the 2025 Corporate Average Fuel Economy (CAFE) standards, three things must happen: customers must look beyond the data sheet and engage materials supplier earlier, and new integrated multi-materials are needed to make step-change improvements.
3D printing, 4D printing, and various types of additive manufacturing (AM) will get even bigger in 2015. We're not talking about consumer use, which gets most of the attention, but processes and technologies that will affect how design engineers design products and how manufacturing engineers make them. For now, the biggest industries are still aerospace and medical, while automotive and architecture continue to grow.
More and more -- that's what we'll see from plastics and composites in 2015, more types of plastics and more ways they can be used. Two of the fastest-growing uses will be automotive parts, plus medical implants and devices. New types of plastics will include biodegradable materials, plastics that can be easily recycled, and some that do both.
Focus on Fundamentals consists of 45-minute on-line classes that cover a host of technologies. You learn without leaving the comfort of your desk. All classes are taught by subject-matter experts and all are archived. So if you can't attend live, attend at your convenience.