What polyurea is
Polyurea is a spray-applied elastomer formed when two liquid components, an isocyanate and an amine resin blend, meet at high pressure in the spray gun. It gels in seconds, builds thick in a single visit, and bonds to concrete, masonry, steel and timber3. It is already a workhorse for truck-bed liners and pipeline coatings because it is durable and watertight3.
For blast work, the property that matters most is elongation. Composite retrofits tend to fail at low strains, so the very high elongation of elastomers is considered key under high-strain-rate loads like blast3. Polyurea is also strongly rate-dependent: it behaves differently, and stiffer, when it is loaded fast3.
Not every polyurea is a blast polyurea. Formulations vary widely in set speed, elongation, tear strength and adhesion. Use a system made and documented for blast mitigation, and spray it to the manufacturer's instructions.
The first 100 milliseconds
A blast wave arrives as a near-instant jump in pressure that decays, dips below ambient, and recovers. In AFRL's full-scale wall tests the positive phase lasted only about 10 ms, while the wall's bending response lasted about 60 ms1. That mismatch is why the wall's ability to deform without breaking apart matters so much.
- Load. Reflected pressure slams the exposed face. Unreinforced block cracks at the mortar joints.
- Strain where cracks open. The bond between block and polymer is stronger in shear than the concrete itself, so the polymer stretches mainly where cracks open1.
- Energy into strain. Because the elastomer can stretch without breaking, blast energy is "transferred into viscoelastic strain energy of the wall" instead of fragmenting it2.
- Containment. The cracked wall is kept together by the elastomer and shields against flying debris2. Even where a wall fails, the elastomer has been reported to stay intact and contain the debris3.
What the research shows
AFRL's Force Protection Branch at Tyndall AFB evaluated 21 candidate polymers, chose a pure polyurea, and tested 12 coated walls in seven full-scale explosive tests. Every uncoated control wall failed catastrophically. Coated one-way walls resisted about a 10-fold increase in peak pressure without catastrophic collapse1.
In the original proof-of-concept tests, about 1/8 in. (3.2 mm) of polyurea on the interior face cut the explosion distance that caused catastrophic failure by up to 80%1.
Analysis of a coated 10 ft block wall found the elastomer's key role is keeping fragments together. "Without the elastomer, CMU blocks would have separated into flying debris"2.
A strain-rate-hardening elastomer developed after the USS Cole attack was fielded as spray-on up-armor on Marine Corps vehicles in Iraq, saving 2,000 lb per vehicle over steel add-on armor6.
Polyurea on the back face of steel improved blast performance. A layer on the blast-receiving face amplified the initial shock loading8. Placement is a design decision.
A 2015 review calls elastomeric retrofitting a cost- and time-effective technique that reduces damage, fragmentation and occupant casualties3. Recent modeling again found polyurea keeps the back face of a wall largely intact4.
Details that decide performance
The research is as clear about what goes wrong as about what goes right. These are the details a blast mitigation coating expert owns.
Bond and surface prep
AFRL called the bond "critical for the effectiveness demonstrated"1. Clean, sound, profiled and dry substrate is not optional.
Edge attachment
Tearing or loss of adhesion at the supports is a path to collapse. A simple 6 in. (15 cm) spray overlap onto the host structure was enough to transfer the load in AFRL testing1.
Which face
For masonry walls, the tested retrofit is on the interior (protected) face1. On steel, back-face polyurea helped while blast-face polyurea amplified the initial shock8.
Thickness and elongation
Thickness and elongation, which govern how much strain energy the coating can absorb, affected wall displacement more than stiffness did1. Thickness matters most at high loads4.
Openings
Walls with windows and doors saw more tearing at the frames and more breaching1. Detail openings and penetrations deliberately.
Quality records
Results are sensitive to "inconsistencies in polymer thickness or continuity over surface irregularities"1. Measure, record and keep the batch numbers.
Standards and where coatings fit
UFC 4-010-01, the DoD Minimum Antiterrorism Standards for Buildings (2018, Change 3 in 2024), applies to all DoD inhabited buildings. It is mandatory for existing buildings when a renovation exceeds 50% of replacement cost or occupancy changes, and it prohibits unreinforced masonry for the exterior walls of new construction5. That leaves a large inventory of existing unreinforced walls, which is exactly where polymer retrofits were developed.
Other programs set their own rules. DoD leased space off installations follows the Interagency Security Committee (ISC) standard5. Process plants assess occupied buildings under guidance such as API RP 75219. Battery energy storage follows NFPA 855, which requires explosion control by venting or prevention systems, not coatings1213.
A note on claims. These standards set performance requirements for buildings and systems. No coating is "certified" to them on its own. A credible blast mitigation applicator supplies tested material to the engineer's design and documents the installation.
Polyurea vs. epoxy, acrylic and polyurethane
All four chemistries have a place in protective coatings. For holding a cracking wall together, the deciding property is the ability to stretch, which AFRL found matters more than stiffness1. Here is how the families typically compare for blast debris mitigation.
| Typical characteristic | Polyurea | Polyurethane | Elastomeric acrylic | Epoxy |
|---|---|---|---|---|
| Stretch before tearing | Very high | Moderate to high | Moderate, in thin films | Low (rigid) |
| Set time | Seconds | Minutes to hours | Hours | Hours |
| Thickness in one visit | Thick, multi-pass in minutes | Moderate | Thin | Moderate |
| Role in a blast retrofit | Primary debris-retaining membrane | Possible membrane, slower build | Weathering topcoat | Bonding agent, rigid strengthening |
| Application temperature window | Broad (UltraBlast: 18°F to 150°F) | Moderate | Weather-limited | Moderate, slow cure in cold |
General characteristics of each coating family. Individual products vary; always use the manufacturer's data sheet.
UltraBlast™ polyurea
UltraBlast is ArmorThane's blast mitigation polyurea. It is a two-component, 100% solids system that can be sprayed at temperatures from 18°F to 150°F and handles service temperatures from -40°F to 350°F, on concrete, metal and plastic substrates17. It forms a strong skin that holds structures together and reduces fragmentation17.
ArmorThane was selected to assist NATO with blast mitigation testing in Spain, using 25 kg and 60 kg dynamite charges at 5 meters17.
Request UltraBlast technical data- System
- 2-component polyurea
- Solids
- 100%
- Spray temperature
- 18°F to 150°F
- Service temperature
- -40°F to 350°F
- Substrates
- Concrete, metal, plastic