# Polyurea
**Polyurea** is a polymer whose macromolecules contain ureylene (urea) linkages, \( \mathrm{-NR-CO-NR-} \), in the backbone, where R is hydrogen, alkyl, aryl, or a substituted form of these; IUPAC excludes amino polymers prepared from urea and an aldehyde, and polymers carrying only pendant ureylene groups, from the class name.[1](https://doi.org/10.1351/goldbook.15308) In practice the material is made by reacting isocyanate components (R-NCO) with amino components (R-NH2), and it is treated as a variant of polyurethane in which the urea linkage replaces the carbamate (urethane) group.[2](https://www.sciencedirect.com/science/article/pii/S0300944025000761) • [3](https://pmc.ncbi.nlm.nih.gov/articles/PMC8708372/) The extremely fast amine-isocyanate reaction makes two-component spray-applied polyurea elastomers possible, and the resulting coatings and linings are used for waterproofing, corrosion protection, and blast and impact mitigation.[2](https://www.sciencedirect.com/science/article/pii/S0300944025000761) • [4](https://pmc.ncbi.nlm.nih.gov/articles/PMC9269495/)
| Key fact | Detail |
|---|---|
| Defining structure | Ureylene linkages \( \mathrm{-NR-CO-NR-} \) in the backbone; amino polymers from urea plus an aldehyde are excluded by the IUPAC definition[1](https://doi.org/10.1351/goldbook.15308) |
| Reaction chemistry | Isocyanate plus primary/secondary amine gives urea linkages with second-order kinetics and rate constants 10 to 100 times those of isocyanate-alcohol (polyurethane) reactions[5](https://www.sciencedirect.com/science/article/pii/S0254058426008953) |
| Moisture tolerance | Insensitive to moisture during cure because the amine-isocyanate reaction outcompetes the isocyanate-water reaction that generates CO2 and foams polyurethanes[5](https://www.sciencedirect.com/science/article/pii/S0254058426008953) |
| Morphology | Alternating soft and hard segments microphase-separate; hard domains are restricted to under 100 nm and act as physical cross-links and reinforcing fillers[3](https://pmc.ncbi.nlm.nih.gov/articles/PMC8708372/) |
| Mechanical behavior | Highly elastic and abrasion resistant at room temperature, with elongation up to 800% before rupture; strongly strain-rate sensitive, stiffening toward glassy behavior under high-rate impact[3](https://pmc.ncbi.nlm.nih.gov/articles/PMC8708372/) • [4](https://pmc.ncbi.nlm.nih.gov/articles/PMC9269495/) |
| Spray technology | Pioneered when Primeaux II of the American Texaco Company (now Huntsman Corporation) introduced amine-terminated polyethers into the B component, replacing hydroxyl-terminated polyethers[2](https://www.sciencedirect.com/science/article/pii/S0300944025000761) |
| Chemical resistance | Resistant to bases, organic acids up to 10% concentration, inorganic acids up to 20%, and their salts, supporting use in sewage and chemical-waste tanks[4](https://pmc.ncbi.nlm.nih.gov/articles/PMC9269495/) |
## Chemistry and synthesis
Polyurea synthesis is a step-growth polyaddition of an isocyanate monomer or prepolymer and a polyamine, each with functionality of at least 2.[6](https://pmc.ncbi.nlm.nih.gov/articles/PMC10893384/) The urea linkages form with second-order kinetics, and the rate constants of the amine-isocyanate reaction are 10 to 100 times those of the isocyanate-alcohol reactions used for polyurethanes.[5](https://www.sciencedirect.com/science/article/pii/S0254058426008953) This speed is what separates polyurea processing from polyurethane processing: the diamine-diisocyanate pathway has extremely fast room-temperature kinetics that enable industrial reaction injection molding (RIM), a process of particular importance in the automotive industry.[7](https://pmc.ncbi.nlm.nih.gov/articles/PMC10489811/)
**Moisture tolerance.** Because the amine-isocyanate reaction is favored over the isocyanate-water reaction, which generates CO2 and causes foaming in polyurethanes, polyurea is insensitive to moisture during cure. This makes it feasible to apply coatings at 100% relative humidity, on damp substrates, and in submerged conditions, while some epoxy coatings can be applied to damp or wet substrates, as substrate requirements vary by formulation.[5](https://www.sciencedirect.com/science/article/pii/S0254058426008953) • [17](https://www.ppg.com/en-US/pmc/product/aquatapoxy-a-6-thick/146040005)
Alternative routes avoid isocyanates altogether. Thermoplastic polyurea elastomers have been synthesized isocyanate- and solvent-free from urea as a non-toxic monomer, and preparative routes using harmless reagents such as CO2 and NH3 have been described for the class generally.[8](https://pubs.rsc.org/en/content/articlepdf/2020/ra/d0ra02369h) • [3](https://pmc.ncbi.nlm.nih.gov/articles/PMC8708372/)
## History of spray polyurea
The development of polyurea elastomer material passed through four stages, according to a 2025 review.[2](https://www.sciencedirect.com/science/article/pii/S0300944025000761) Bayer Corporation successfully developed reaction injection molding technology, laying the foundation for spray polyurea.[2](https://www.sciencedirect.com/science/article/pii/S0300944025000761) Spray application became practical when Primeaux II, working at the American Texaco Company (today's [Huntsman Corporation](https://www.edgepedia.org/huntsman-corporation)), put amine-terminated polyethers into the B component in place of the hydroxyl-terminated polyethers used before, thereby launching spray polyurea elastomer (SPUA) technology around the world.[2](https://www.sciencedirect.com/science/article/pii/S0300944025000761) Spray polyurea elastomer technology was developed by Primeaux in the 1980s as a rapid prototyping system based on RIM, successfully applied to both aromatic and aliphatic spray polyurea elastomers.[4](https://pmc.ncbi.nlm.nih.gov/articles/PMC9269495/)
## Structure and morphology
Polyurea is a segmented copolymer composed of soft segments and hard segments arranged alternately.[9](https://www.mater-rep.com/EN/10.11896/cldb.19070177) The two block types are thermodynamically incompatible and microphase-separate: the soft segments form a continuous matrix, while the hard segments disperse randomly as nanodomains restricted to under 100 nm in size.[3](https://pmc.ncbi.nlm.nih.gov/articles/PMC8708372/) The multifunctional hard-segment domains serve as both physical cross-links and reinforcing fillers, and high mechanical toughness results from extensive intermolecular hydrogen bonding in the hard domains.[3](https://pmc.ncbi.nlm.nih.gov/articles/PMC8708372/)
**Hydrogen bonding.** The mechanical advantage of polyurea over polyurethane comes from bidentate hydrogen bonding between urea groups (N-H to the carbonyl oxygen), which generates hard-domain cohesion energy densities 40 to 60% greater than polyurethanes, where each urethane group forms only a single hydrogen bond.[5](https://www.sciencedirect.com/science/article/pii/S0254058426008953) The polarity, symmetry, crystallinity, and hydrogen bonding of the soft and hard segments all affect the degree of microphase separation, which in turn governs mechanical and self-healing properties.[10](https://pmc.ncbi.nlm.nih.gov/articles/PMC12097089/) Soft-segment resins commonly used in production include [polypropylene glycol](https://www.edgepedia.org/polypropylene-glycol) (PPG), polycaprolactone (PCL), polytetrahydrofuran (PTMEG), polydimethylsiloxane (PDMS), and polycarbonate of various molecular weights.[10](https://pmc.ncbi.nlm.nih.gov/articles/PMC12097089/)
## Mechanical behavior and impact protection
At room temperature polyurea is highly elastic, resistant to abrasion, and can undergo up to 800% elongation prior to rupture; its viscoelastic properties depend on pressure, temperature, and strain rate.[3](https://pmc.ncbi.nlm.nih.gov/articles/PMC8708372/) The material is significantly strain-rate sensitive: its mechanical properties change noticeably under high strain-rate loads, and behavior shifts from rubbery toward glassy under high-rate deformation, a transition closely related to the glass transition.[4](https://pmc.ncbi.nlm.nih.gov/articles/PMC9269495/) Under impact, transient hardening toward a glassy state increases the modulus by about three orders of magnitude, spreading the impact force laterally and reducing impact pressure.[4](https://pmc.ncbi.nlm.nih.gov/articles/PMC9269495/) This dynamic rubber-to-glass transition is the mechanism most often cited for ballistic protection, while blast mitigation is attributed to shock-wave capture and neutralization.[11](https://pubs.rsc.org/en/content/articlelanding/2016/ra/c6ra23866a/unauth)
**Coating position matters.** Studies of coated metal plates give position-dependent results. Metal plates coated on the front (impact) face showed a more pronounced increase in ballistic limit and specific energy absorption than backside-coated plates, and backside spraying with high-hardness polyurea decreased total ballistic performance in one study; early studies had found no benefit for steel plates when rigid polyurea was used.[4](https://pmc.ncbi.nlm.nih.gov/articles/PMC9269495/) For underwater explosions the pattern differs: an aluminum plate coated on the frontside had the least severe plastic deformation under the shock wave, while coating both sides produced the largest deformation, contrary to the airborne-explosion case.[4](https://pmc.ncbi.nlm.nih.gov/articles/PMC9269495/) In implosion tests, polyurea delayed the pulse enough to reduce peak energy values by 35% for external coatings and 50% for internal coatings.[4](https://pmc.ncbi.nlm.nih.gov/articles/PMC9269495/) For concrete structures, backside coating of the blast face has been found the most effective protection measure, and full-area backside spraying outperforms partial spraying because confined coating boundaries absorb energy through tensile deformation and peeling.[4](https://pmc.ncbi.nlm.nih.gov/articles/PMC9269495/)
Because quasi-static properties differ so much from high-rate behavior, quasi-static mechanical properties are treated as referential parameters in blast and impact design, not core parameters.[4](https://pmc.ncbi.nlm.nih.gov/articles/PMC9269495/) Formulation levers include the hard/soft segment ratio, crosslinker content (low tensile strength at 1.2 mol% crosslinker but high strain-rate sensitivity), and chain extenders, which drive phase separation and hard-segment formation.[4](https://pmc.ncbi.nlm.nih.gov/articles/PMC9269495/)
## Coatings and applications
Polyurea spray coatings cure rapidly even at sub-zero temperatures and offer high hardness, flexibility, tear strength, tensile strength, and chemical and water resistance.[5](https://www.sciencedirect.com/science/article/pii/S0254058426008953) Chemical resistance to bases, organic acids up to 10%, inorganic acids up to 20%, and their salts makes the material applicable to tanks used for municipal sewage purification and some chemical wastes.[4](https://pmc.ncbi.nlm.nih.gov/articles/PMC9269495/) In infrastructure comparisons covering 127 projects worldwide, waterproof-elastic polyurea-type systems showed 75% less frequent maintenance than traditional systems when delayed penalties, material prices, labor, and service life were accounted for.[5](https://www.sciencedirect.com/science/article/pii/S0254058426008953)
**Limitations.** Outdoor UV radiation, being higher in energy than the activation energy of the polymer, changes the segmental microstructure and accelerates aging, damaging mechanical and physical properties.[4](https://pmc.ncbi.nlm.nih.gov/articles/PMC9269495/) The fast reaction is itself a constraint: because the coating is highly reactive and quick-curing, setting without adequate wetting-out time can cause poor adhesion to the substrate.[12](https://ama-india.org/wp-content/uploads/2025/08/Jun19-8-25.pdf) Reviews of the field also list the excessively rapid reaction kinetics, limited control of network topology, and restricted functional diversity as inherent challenges, with recent strategies using low-reactivity amines or blocking approaches to modulate kinetics and dynamic covalent bonds or hydrolysable groups to enable recycling and self-healing.[13](https://pubmed.ncbi.nlm.nih.gov/42268216/) • [6](https://pmc.ncbi.nlm.nih.gov/articles/PMC10893384/) • [10](https://pmc.ncbi.nlm.nih.gov/articles/PMC12097089/)
## Application practice and surface preparation
Surface preparation is the single most critical factor in the long-term success of a polyurea coating project; industry data attribute coating failures to inadequate surface preparation in over 80% of cases.[14](https://americanpolyurea.org/polyurea-surface-preparation-the-complete-field-guide-for-applicators/) Contamination from oil, grease, existing coatings, salts, or rust creates a weak boundary layer that eventually delaminates under thermal cycling, impact, or hydrostatic pressure.[14](https://americanpolyurea.org/polyurea-surface-preparation-the-complete-field-guide-for-applicators/) For external pipe surfaces, one specification requires application to properly prepared surfaces within 8 hours of blasting, prohibits application to wet surfaces or when relative humidity exceeds 80%, and requires the surface temperature to be at least 5°F above the dew point.[15](https://specialty-products.com/wp-content/uploads/2015/06/PREPARATION-GUIDE-FOR-EXTERNAL-PIPE-SURFACES.pdf) Manufacturers likewise report sensitivity to moisture when the substrate is less than 3°C above the dew point at application, since trapped moisture can penetrate the freshly applied coating before a film forms.[16](https://www.helios-profi.com/en/news/pogoste-tezave-s-polisecninskimi-premazi) Primers are used to improve adhesion on smooth surfaces, mitigate moisture in concrete, and inhibit corrosion on steel.[14](https://americanpolyurea.org/polyurea-surface-preparation-the-complete-field-guide-for-applicators/)
## Current research directions
Recent reviews frame the field around controlling the very speed that makes polyurea useful. Topology-regulated polyurea research employs low-reactivity amines or blocking approaches to modulate reaction kinetics, engineers network topology precisely, and broadens applications toward impact protection, functional coatings, adhesives, and flexible electronics.[13](https://pubmed.ncbi.nlm.nih.gov/42268216/) Self-healing polyurea based on dynamic chemistry is an active area, exploiting the sensitivity of the microphase structure to segment structure, crystallinity, polarity, symmetry, and hydrogen bonding.[10](https://pmc.ncbi.nlm.nih.gov/articles/PMC12097089/) Isocyanate-free routes from urea monomers address environmental concerns, and copolymers and non-isocyanate polyureas are expected to see wider use.[8](https://pubs.rsc.org/en/content/articlepdf/2020/ra/d0ra02369h) • [2](https://www.sciencedirect.com/science/article/pii/S0300944025000761)
## References
1. [IUPAC Compendium of Chemical Terminology, 'polyurea' (15308), 5th ed., 2025](https://doi.org/10.1351/goldbook.15308)
2. [Polyurea: Evolution, synthesis, performance, modification, and future directions, Progress in Organic Coatings (2025)](https://www.sciencedirect.com/science/article/pii/S0300944025000761)
3. [Santana et al., Polyureas Versatile Polymers for New Academic and Technological Applications, Polymers 13(24), 4393 (2021)](https://pmc.ncbi.nlm.nih.gov/articles/PMC8708372/)
4. [Polyurea for Blast and Impact Protection: A Review, Polymers 14, 2670 (2022)](https://pmc.ncbi.nlm.nih.gov/articles/PMC9269495/)
5. [Structure-property relationships in tailored polyurea coatings: A review, Progress in Organic Coatings (2026)](https://www.sciencedirect.com/science/article/pii/S0254058426008953)
6. [State-of-the-Art Polyurea Coatings: Synthesis Aspects, Structure-Properties Relationship, and Nanocomposites for Ballistic Protection Applications (2024)](https://pmc.ncbi.nlm.nih.gov/articles/PMC10893384/)
7. [Chemical Structure and Side Reactions in Polyurea Synthesized via the Water-Diisocyanate Synthesis Pathway, Polymers (2022)](https://pmc.ncbi.nlm.nih.gov/articles/PMC10489811/)
8. [Isocyanate- and solvent-free synthesis of melt processible polyurea elastomers derived from urea as a monomer, RSC Advances (2020)](https://pubs.rsc.org/en/content/articlepdf/2020/ra/d0ra02369h)
9. [A Review on the Microphase Separation of Polyurea Elastomers, Materials Reports (2019)](https://www.mater-rep.com/EN/10.11896/cldb.19070177)
10. [The Latest Advances in Mechanically Robust Self-Healing Polyurea Based on Dynamic Chemistry (2024)](https://pmc.ncbi.nlm.nih.gov/articles/PMC12097089/)
11. [Polyurea coatings for enhanced blast-mitigation: a review, RSC Advances (2016)](https://pubs.rsc.org/en/content/articlelanding/2016/ra/c6ra23866a/unauth)
12. [Preparing the surface, AMA technical note (2025)](https://ama-india.org/wp-content/uploads/2025/08/Jun19-8-25.pdf)
13. [Topology-Regulated Polyurea: From Structural Design to Emerging Applications (2025)](https://pubmed.ncbi.nlm.nih.gov/42268216/)
14. [Polyurea Surface Preparation: The Complete Field Guide for Applicators, American Polyurea (2026)](https://americanpolyurea.org/polyurea-surface-preparation-the-complete-field-guide-for-applicators/)
15. [Preparation Guide for External Pipe Surfaces, Specialty Products, Inc.](https://specialty-products.com/wp-content/uploads/2015/06/PREPARATION-GUIDE-FOR-EXTERNAL-PIPE-SURFACES.pdf)
16. [The importance of substrate preparation when installing polyurea for flat roofs, Helios](https://www.helios-profi.com/en/news/pogoste-tezave-s-polisecninskimi-premazi)
17. [PPG](https://www.ppg.com/en-US/pmc/product/aquatapoxy-a-6-thick/146040005)
---
*Topic: Encyclopedia › Physical world and mathematics › Chemistry › Organic substances › Organic reactions, structure and reference › Organic polymer classes › Step-growth polymer classes › Novel and specialty step-growth backbones*
*Initially written Sep 17, 2026 · Reviewed: Oct 15, 2026 · Edited: Oct 15, 2026 · Last review: Oct 15, 2026*
*Copyright 2026 EdgeChat AI, a subsidiary of Biostate AI.*
License: Edgepedia Community License 1.0, https://www.edgepedia.org/edgepedia/license