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A cue from nature to create bulletproof coatings


Researchers from the University of Houston are using chitin to produce high-impact multilayered coatings that can protect against bullets, lasers, toxic gas and other dangers.

Chitin offers promise as a commonly available material that could be processed and used in some products that now require petroleum-based plastics, said Alamgir Karim, Dow Chair Professor of chemical and biomolecular engineering.

Karim, who also serves as director of the International Polymer & Soft Matter Center and of the materials engineering program at UH, is principal investigator on the project. Venkatesh Balan, assistant professor of engineering technology, and Megan Robertson, associate professor of chemical and biomolecular engineering, are co-principal investigators.

They are charged with developing tough, durable and antimicrobial multilayer films capable of resisting an impact from projectiles or lasers while simultaneously absorbing toxic gas. Karim said the work will also have applications beyond the military, potentially expanding its environmental benefits.

Primary component of cell walls in fungi and the exoskeletons of arthropods

Chitin is the primary component of cell walls in fungi and the exoskeletons of arthropods, including crustaceans, insects and mollusks. It’s also found in fish scales. It can be harvested and processed to produce chitosan, or de-acetylated chitin. Chitosan is easier to handle than the brittle chitin.

Balan, whose lab produces bio-molecules for medical and industrial use, is using chemical and enzymatic processes to produce the chitosan molecules using crustacean shells. "We are trying to do the same thing with mushrooms,” he said, noting that mushrooms yield a more consistent degree of polymerisation sustainably, helping to standardise production of chitin and then process it to become chitosan.

A stable source of chitosan polymers will be just the beginning. Robertson will determine how to alter the atomic composition at the surface of the chitosan in order to improve how it interfaces with the functional layers. Her research includes designing sustainable and biodegradable polymers derived from renewable resources.

Absorbing the impact from a projectile

That enhanced compatibility between the chitosan and the polymer will improve the coating’s ability to trap gas or absorb the impact from a projectile, she said.

That’s where Karim comes in – he is engineering a multilayer system that will be comprised of a hardened impact-resistant layer; an energy-absorbing crush layer reminiscent of the way modern cars are designed to crumple on impact, safeguarding the passenger capsule; a layer to absorb toxic gas, with charcoal nanoparticles dispersed in the chitosan; and a textile adhesion layer, which will bind the coating to canvas and other textiles.

That will involve 3D printing different chitin nanoparticles and chitosan-fabricated or reinforced crush-zone design structures and testing them to determine their ability to withstand an impact.

"It is a very good, environmentally friendly project,” Karim said, and one that will have applications for the automobile, construction and other industries.

Researchers from the University of Houston are using chitin that is found in the exoskeletons of arthropods to produce coatings that can protect against bullets.

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