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May 27, 2023

Researchers have developed a molecule that, when added to a polymer, increases the material’s durability by making it more like metal in terms of its ability to withstand temperature fluctuations. They say it could increase the durability of everything from plastic phone cases to missiles.

Because of their low cost, low density, good thermal and electrical insulation properties and high resistance to corrosion, polymers are found in almost every item used in daily life. However, continued exposure to heat and cold causes materials, including polymers, to expand and contract, which ultimately leads to deterioration.

Different materials expand and contract at different rates – metals and ceramics, for example, contract less than polymers. Researchers from Sandia National Laboratories in the US have modified a molecule that, when added to a polymer, increases the material’s durability to make it more metal-like.

“This really is a unique molecule that when you heat it up, instead of it expanding, it actually contracts by undergoing a change in its shape,” said Erica Redline, a materials scientist who led the research team. “When it’s added to a polymer, it causes that polymer to contract less, hitting expansion and contraction values similar to metals. To have a molecule that behaves like metal is pretty remarkable.”

The idea for developing the game-changing molecule – which the researchers have not named – arose out of fielding complaints from Sandia customers about the fragility of smartphones, which are made of various materials that each react in different ways to heat and cold.

“Take, for example, your phone, which has a plastic housing coupled to a glass screen, and inside that, the metals and ceramics that make up the circuitry,” Redline said. “These materials are all screwed, glued or somehow bonded together and will start expanding and contracting at different rates, putting stresses on one another which can cause them to crack or warp over time.”

The researchers say the molecule could revolutionize how polymers are used in a range of applications, including electronics, communications systems, solar panels, automotive parts, circuit boards, aerospace designs, defense systems, and flooring.

“The molecule not only solves current issues but significantly opens up design space for more innovations in the future,” said Jason Dugger, a Sandia chemical engineer.

They say a benefit is that it can be introduced into different parts of a polymer in different percentages during 3D printing.

“You could print a structure with certain thermal behaviors in one area, and other thermal behaviors in another to match the materials in different parts of the item,” Dugger said.

And it also helps reduce the weight of materials by eliminating heavy fillers. Often, minerals such as calcium carbonate, silica, clay, kaolin and carbon are added as fillers to make the polymer easier to mold and shape and ensure stability.

“It would enable us to do things much lighter to save mass,” said Dugger. “That is especially important when launching a satellite, for example. Every gram we can save is huge.”

The researchers have so far only created small quantities of the molecule, but they’re working on a way of scaling up production. Currently, it takes about 10 days to produce between 0.2 to 0.3 oz (7 to 10 g).

“It’s unfortunately a long synthesis for this molecule,” said Chad Staiger, the organic chemist responsible for creating the molecule. “More steps equal more time and more money. You usually see five- to six-step syntheses in higher-value materials such as pharmaceuticals. In polymers, the cheaper the better for widescale adoption.”

Nonetheless, the researchers remain optimistic about the molecule’s potential uses.

“There’s nothing like it out there,” said Eric Nagel, part of the research team. “I am really excited at the possibilities of what this technology can do and the application that could be associated with this.”

Source: Sandia National Laboratories