New Twisted Nanofibers May Replace Kevlar in Bulletproof Vests

You may soon find some other materials being used in bullet proof vests other than Kevlar. Scientists have created materials that exploit the electromechanical properties of specific nanofibers to stretch up to seven times their length while remaining tougher than Kevlar.

Kevlar, which is often used to make bulletproof vests, can absorb up to 80 joules per gram. Yet this latest material can absorb as much as 98 joules per gram.

How did the researchers create this new material? The scientists twisted nanofiber into yarns and coils. The electricity generated by stretching the twisted nanofiber formed an attraction that was 10 times stronger than a hydrogen bond, which is considered one of the strongest forces formed between molecules.

In this case, the researchers wanted to mimic their earlier work on the piezoelectric action, which is how pressure forms electric charges, of collagen fibers found inside bone.

"We reproduced this process in nanofibers by manipulating the creation of electric charges to result in a lightweight, flexible, yet strong material," said Majid Minary, one of the researchers, in a news release. "Our country needs such materials on a large scale for industrial and defense applications."

The researchers spun nanofibers out of a material known as polyvinylidene fluoride (PVDF) and its co-polymer, polyvinvylidene fluoride trifluoroethylene (PVDF-TrFE). Then the researchers twisted the fibers into yarns, and then into coils.

"Our experiment is proof of the concept that our structures can absorb more energy before failure than the materials conventionally used in bulletproof armors," said Minary. "We believe, modeled after the human bone, that this flexibility and strength comes from the electricity that occurs when these nanofibers are twisted."

The findings are published in the journal ACS Applied Materials & Interfaces.

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