Lightweight and heat-resistant components for Makers of planes, trains, and automobiles could benefit from a manufacturing process that uses a short burst of heat to rapidly cure and harden polymers, according to researchers at the University of Illinois. Writing in the journal Nature recently the team says that their approach reduces energy needed for polymer curing by ten orders of magnitude when compared with conventional manufacturing processes. It also works one hundred times quicker. [S White et al., Nature; DOI: 10.1038/s41586-018-0054-x]
"This development marks what could be the first major advancement to the high-performance polymer and composite manufacturing industry in almost half a century," explains Illinois professor of aerospace engineering Scott White. "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," he adds. "One of our goals is to decrease expense and increase production."
In aircraft manufacture ring curing ovens that are about 20 meters in diameter and 15 meters long are needed. These large industrial structures are filled with heating elements, fans, cooling pipes and other machinery. The temperature is raised to almost 180 degrees Celsius in steps over a 24-hour period in what is a very energy-intensive process. Curing just one section of a large commercial airliner can consume over 96000 kilowatt-hours of energy and produce more than 80 tonnes of carbon dioxide if energy is from non-carbon neutral sources. That's almost the equivalent of powering ten homes for a year.
White, working with chemist Jeffrey Moore, Philippe Geubelle, and materials science and engineering professor Nancy Sottos proposed a method for controlling chemical reactivity in the process so that they could reduce the energy requirements of the polymer-curing process. "There is plenty of energy stored in the resin's chemical bonds to fuel the process," explains Moore. "Learning how to unleash this energy at just the right rate was key to the discovery."
The team uses what is essentially a soldering iron and touches just one corner of polymer surface. This starts a cascade of chemical reactions that propagate as a wave through the material. "Once triggered, 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," White adds.
Sottos adds that it is possible to increase the speed of the process by triggering the hardening reaction from more than one point, in a very carefully controlled way. It is critical to avoid two reaction waves colliding and causing a thermal spike that would lead to imperfections in the product and facilitate degradation over time.
Now that the team has demonstrated how their approach can produce safe, high-quality polymers in a well-controlled laboratory environment, they need to carry out real-world tests. They envision the process accommodating large-scale production due to its compatibility with commonly used fabrication techniques like molding, imprinting, 3D printing, and resin infusion.
David Bradley blogs at Sciencebase Science Blog and tweets @sciencebase, he is author of the popular science book "Deceived Wisdom".