WASHINGTON. U.S. Naval Research Laboratory (NRL) research chemists developed and patented a transparent thermoplastic elastomer armor to reduce weight, inherent in most bullet-resistant glass, while maintaining ballistic properties.
The transparent polymer armorconsists of alternating layers of elastomeric polymer and a harder material substrate. Very small crystalline domains, which also provide rigidity, give the polymer its transparency. Thermoplastic elastomers are soft, rubbery polymers converted by physical means, rather than a chemical process, to a solid. Consequently, the solidification is reversible and enables damaged armor surfaces to be repaired ‘on-the-fly’ in the field.
“Heating the material above the softening point, around 100 degrees Celsius, melts the small crystallites, enabling the fracture surfaces to meld together and reform via diffusion,” says Dr. Mike Roland, senior scientist, NRL Soft Matter Physics. “This can be accomplished with a hot plate, akin to an iron, that molds the newly forming surface into a smooth, flat sheet with negligible effect on integrity.”
NRL scientists tested the use of polymeric materials as a coating to achieve improved impact resistance of hard substrates. The scientists started applying polyurea and polyisobutylene layers, which enhance the ballistic performance of armor and helmets, and achieve greater ballistic effectiveness and mitigation of blast waves.
By using a variation of employing thermoplastic elastomers, NRL scientists are able to recreate superior ballistic properties of polyurea and polyisobutylene coatings, with the added benefit of the material being transparent, lighter than conventional bullet-resistant glass, and repairable.
“Because of the dissipative properties of the elastomer, the damage due to a projectile strike is limited to the impact locus. This means that the affect on visibility is almost inconsequential, and multi-hit protection is achieved,” Roland adds.
NRL’s transparent thermoplastic elastomer armor technology is covered by U.S. Patent #9,285,191; “Polymer Coatings for Enhanced and Field-Repairable Transparent Armor.”