Advances in additive manufacturing technologies happen on the regular, with ever increasing speeds, build sizes, and accuracy. One factor which perhaps doesn’t get enough attention in the development of next-gen manufacturing systems is energy consumption. Now, however, a team of researchers from the University of Illinois are tackling the issue head on with the development of a new polymer-curing process called Frontal Polymerization (FP).
Frontal Polymerization—which could be used to produce strong, heat resistant parts for the automotive and aerospace sectors—is reportedly capable of curing polymers using 10 orders of magnitude less energy than existing systems and can reduce production times by two orders of magnitude.
“This development marks what could be the first major advancement to the high-performance polymer and composite manufacturing industry in almost half a century,” comments Scott White, an aerospace engineering professor at U of I and lead author of the study. “The materials used to create aircraft and automobiles have excellent thermal and mechanical performance, but the fabrication process is costly in terms of time, energy and environmental impact. One of our goals is to decrease expense and increase production.”
The Frontal Polymerization process uses a small heat source (likened to a soldering iron), which briefly comes into contact with the tip of a printed polymer surface. This encounter sends a “hardening wave” through the polymer, effectively solidifying the printed polymer. In more precise terms, by touching the soldering iron to the corner of the printed polymer, a “cascading chemical-reaction” is initiated. “Once triggered,” continues White. “The reaction uses enthalpy, or the internal energy of the polymerization reaction, to push the reaction forward and cure the material, rather than an external energy source.”
The U of I researchers have compared their polymer-curing process to existing curing systems employed by aircraft producers to show how energy efficient the new process is. Presently, the researchers say that to cure a “section of a large commercial airliner” can use over 96,000 kilowatt-hours of energy and produce more than 80 tons of CO2. To put that amount into perspective, it is about the same amount of energy than nine households would consume in a year.
“The airliner manufacturers use a curing oven that is about 60 feet in diameter and about 40 feet long—it is an incredibly massive structure filled with heating elements, fans, cooling pipes and all sorts of other complex machinery,” explains White. “The temperature is raised to about 350 degrees Fahrenheit in a series of very precise steps over a roughly 24-hour cycle. It is an incredibly energy-intensive process.”
By contrast, Frontal Polymerization could dramatically reduce energy consumption and overall curing times for a range of large-scale manufacturing methods, including 3D printing, molding, imprinting, and more. So far, the team has shown the technique’s suitability for producing safe and high quality parts in a controlled setting.
Of course, there is still work to be done before the Frontal Polymerization process will hit the commercial market, as the researchers want to ensure that the quality of the cured polymer parts are up to standard. A key part of improving the polymer-curing technique will depend on “unleashing” the energy stored within the polymer resins in a controlled and precise way.
“You can save energy and time, but that does not matter if the quality of the final product is substandard,” said Nancy Sottos, a materials science and engineering professor who is working on the project. “We can increase the speed of manufacturing by triggering the hardening reaction from more than one point, but that needs to be very carefully controlled. Otherwise, the meeting spot of the two reaction waves could form a thermal spike, causing imperfections that could degrade the material over time.”
The U of I team, which recently published its research in the journal Nature, is part of the Beckman Institute for Advanced Science and Technology, itself part of the University of Illinois at Urbana-Champaign.