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USA:Textile researchers produce super-strong nylon fibers |
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2004-9-27
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Triangle - Raleigh - Nylon fibers have many uses, from clothes and carpets to rope and the case that surrounds your computer monitor. Now researchers at North Carolina State University’s College of Textiles, who are trying to improve nylon, have created the strongest aliphatic nylon fibers ever reported.
Dr. Alan Tonelli, KoSa Professor of Polymer Science, and Dr. Richard Kotek, assistant professor of textile engineering, chemistry and science, are investigating methods of creating stronger nylon fibers without the expense of current, sometimes complicated, processes. They are working with aliphatic nylon, or nylon whose carbon atoms are joined together in straight or branched open chains rather than in rings.
Stronger aliphatic nylon could be used in ropes, loading straps, parachutes and automotive tires, or to create composite materials suitable for high-temperature applications.
The findings were recently presented at the American Chemical Society annual meeting in Philadelphia and published in the journal Polymer.
Fibers are made up of polymers, or long chain molecules containing many repeating units. When those chains are arranged in a neat, orderly manner, the polymer is said to be crystalline – like a box of uncooked spaghetti. Other times, there is no order and the polymer chains are randomly coiled up – think of a bowl of cooked spaghetti – and referred to as amorphous.
The coiled-up polymers need to be stretched out and have their elasticity removed if they are to be made into strong fibers. Hydrogen bonds between nylon chains prohibit their stretching and alignment, so overcoming these bonds may be the key to creating stronger nylon fibers.
Super-strong fibers, like Kevlar for example, are created from so-called aromatic nylon polymers – very stiff, long chains containing rings. Unfortunately, aromatic nylon is very difficult to work with and, as a result, very expensive.
So Tonelli and Kotek have been using polyamide 66, also known as nylon 66, a commercial thermoplastic that is easier to work with, but difficult to stretch and align. It’s also difficult to remove the elasticity from nylon 66, the researchers say.
They discovered that by dissolving the nylon 66 in a solution of a chemical agent called gallium trichloride, they could effectively break up the hydrogen bonds. That allows the polymer chains to be stretched out. “Once the fiber is created, it is soaked in water to wash away the gallium trichloride, allowing the hydrogen bonds to re-establish,” Tonelli said.
According to Kotek, the resulting fibers are very strong. “It looks promising; we’ve had good results and this looks like a more straightforward approach. Just on the first try we’re getting strong fibers,” he said.
Tonelli says these new fibers are perhaps as much as 10 times stronger than typical aliphatic nylons. “We did a literature search and these are the strongest aliphatic nylon fibers reported. All kinds of techniques have been used to improve them – all by trying to modify the hydrogen bonds,” he said.
Using aliphatic nylon might even be more economical to produce. “High strength fibers like Kevlar® must be made in specialized factories due to the concentrated sulfuric acid used in its production. This product could be made in an ordinary fiber-spinning operation that currently exists. There’s nothing peculiar about the process,” Tonelli said.
Tonelli and Kotek are continuing with their research. They’re currently looking at what the results would be if all the hydrogen bonds were not broken and how that affects the strength of the resulting nylon 66 fibers. |
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