Your formulation team wants a fast-return, non-yellowing protective coating. The job spec on the next bid says “polyurea.” The incumbent product the customer is replacing is a “2K polyurethane,” and a competitor is pitching “polyaspartic.” Before you can cost a build or send an RFQ, you have to answer a sourcing question, not a marketing one: which isocyanate, which amine or polyol, and which intermediate actually goes into each of these. This is the raw-material guide to that decision, written for the buyer sourcing the feedstock, not the contractor pricing a floor.
The short version: Polyurethane (PU), polyurea, and polyaspartic differ by one variable: what the isocyanate reacts with. PU couples an isocyanate (–NCO) with a polyol (–OH) and cures slowly with a long, catalyst-tunable pot life. Polyurea couples an isocyanate with an amine (–NH₂); that reaction is so fast that pure systems gel in seconds and have to be applied through heated plural-component spray. Polyaspartic is a subclass of polyurea that replaces the fast amine with a hindered *aspartic ester*, a bulky secondary diamine whose steric bulk slows the reaction down to a tunable pot life of minutes to hours while keeping a non-yellowing aliphatic backbone. The feedstock follows directly: PU needs a polyol plus an isocyanate; polyurea needs amine-terminated resins plus a low-molecular-weight diamine chain extender; polyaspartic needs an aspartic ester (made from a diamine and a dialkyl maleate such as diethyl maleate) plus an aliphatic isocyanate.
One reaction, three partners
All three chemistries start from the same reactive group: the isocyanate (–NCO), which is hungry for anything carrying an active hydrogen. Change the partner and you change the linkage, the cure speed, and the entire raw-material bill.
React –NCO with a hydroxyl (–OH) on a polyol and you build a urethane linkage: that is polyurethane. React –NCO with a primary or secondary amine (–NH) and you build a urea linkage, with no catalyst needed: that is polyurea. Amines are far more nucleophilic than hydroxyls, so the amine–isocyanate reaction runs orders of magnitude faster than the hydroxyl–isocyanate reaction. Polyaspartic is simply a clever way to slow that amine reaction back down without giving up the urea linkage or the weatherable backbone.
Hold onto one naming trap. Polyurea and polyurethane are *resin chemistries* defined by the reaction partner; “polyaspartic” names the partner itself (the aspartic ester). A cured polyaspartic film is technically an aliphatic polyurea. Suppliers and spec writers use the three names as if they were peers, so the practical question for a buyer is always the same: what is on each side of the mix.
Polyurethane: isocyanate plus polyol
A 2K polyurethane is the most versatile and the most forgiving of the three. The polyol side carries the –OH groups and sets flexibility, hardness, and chemical resistance; the isocyanate side crosslinks it. Because the hydroxyl reaction is comparatively slow, PU systems give you a long working window, accept catalysts to dial the cure, and tolerate thicker pours, which is why the same chemistry spans foams, elastomers, adhesives, and coatings.
The isocyanate you choose decides whether the film yellows. Aromatic isocyanates such as polymeric MDI are economical and fast, but the aromatic ring photo-oxidizes into colored chromophores under UV, so they amber outdoors and belong in primers, foams, adhesives, and hidden layers. The polymeric MDI (PMDI) you would source for rigid foam or a structural binder is the same family that yellows in sunlight. When the layer has to stay clear and glossy outdoors, you move to an aliphatic isocyanate: an HDI biuret, an HDI isocyanurate trimer, or isophorone diisocyanate (IPDI). The full grade-by-grade comparison lives in our guide to choosing an aliphatic (non-yellowing) isocyanate. The trade-off is cost and speed: aliphatics carry a price premium and generally react slower, so reserve them for the layer the sun hits.
Polyurea: isocyanate plus amine
Pure (two-component) polyurea is the speed play. The amine side, usually a blend of an amine-terminated polyether resin plus a low-molecular-weight diamine chain extender, reacts with the isocyanate side almost on contact. Gel times of a few seconds and tack-free in well under a minute are normal. That speed buys two real advantages: the coating builds film in a single pass at high thickness, and because the amine grabs the isocyanate far faster than ambient water can, it cures largely insensitive to humidity, where a urethane might blister.
The feedstock reflects the architecture. The flexible “soft segment” comes from amine-terminated polyethers; polyetheramine D-2000 (a difunctional polyoxypropylene diamine, ~2,000 g/mol) and the trifunctional polyetheramine T-5000 are the workhorse backbones for impact resistance, flexibility, and low-temperature performance. The “hard segment” comes from a short diamine chain extender that raises crosslink density and hardness. Fast aromatic spray systems typically use an aromatic chain extender (DETDA-type), which we do not stock; for slower, non-yellowing aliphatic polyurea, cycloaliphatic and araliphatic diamines such as isophorone diamine (IPDA) and m-xylylenediamine (MXDA) serve that role.
Here is the honest catch for anyone scoping a polyurea line. That same speed that makes pure polyurea attractive is also its constraint. Gel-in-seconds chemistry cannot be brushed, rolled, or hand-mixed in a bucket; it requires heated, high-pressure plural-component equipment that meters the two streams at roughly 2,000–3,000 psi and impingement-mixes them at the gun. If you are not committed to spray application and that capital, the chemistry you actually want is probably polyaspartic.
Polyaspartic: the hindered-amine subclass with a dial for pot life
Polyaspartic solves the polyurea pot-life problem at the molecular level. The amine is replaced by a polyaspartic ester (an aspartic ester resin), which is a *secondary* diamine carrying two bulky ester groups right next to the reactive nitrogen. That steric crowding slows the amine–isocyanate reaction from seconds to a controllable pot life, reported across the literature in the range of roughly 15–40 minutes and tunable from minutes to hours by changing the diamine and ester. You keep the urea linkage and the toughness; you regain a brush-, roll-, and squeegee-friendly working window.
The aspartic ester itself is made by an aza-Michael addition: a primary diamine adds across the activated double bond of a dialkyl maleate, converting the primary amine to the hindered secondary amine. Diethyl maleate (DEM) is the usual dialkyl maleate for that step, and the diamine is typically a cycloaliphatic or araliphatic type such as IPDA or MXDA. The result reacts with an aliphatic polyisocyanate (HDI trimer or IPDI chemistry), which is what makes a polyaspartic non-yellowing: there is no aromatic ring at the reactive site to form chromophores under UV. Be clear on scope here. RawSource supplies the building blocks, the DEM feedstock, the diamines, and the aliphatic isocyanates that go *into* an aspartic-ester polyurea; we do not sell finished, formulated polyaspartic-ester resins or phenalkamine systems.
Side by side: reaction partners, cure, weatherability, raw materials
Match the chemistry to the constraint your specification is actually gated on, then source the feedstock that chemistry demands.
| Polyurethane (PU) | Polyurea | Polyaspartic | |
|---|---|---|---|
| Isocyanate reacts with | Polyol (–OH) → urethane | Amine (–NH₂) → urea | Aspartic ester (hindered –NH) → urea |
| Cure speed / pot life | Slow; long, catalyst-tunable pot life (minutes to hours) | Ultra-fast; gel in seconds, little to no pot life | Tunable; pot life ~15–40 min (minutes to hours by design) |
| Application | Brush, roll, cast, pour, spray | Heated plural-component spray (impingement, ~2,000–3,000 psi) | Brush, roll, squeegee, spray |
| Weatherability | Aromatic yellows; aliphatic is non-yellowing | Aromatic (typical spray) yellows; aliphatic versions cost/slow more | Non-yellowing (aliphatic isocyanate) |
| Key raw materials | Polyol + isocyanate (PMDI aromatic, or HDI/IPDI aliphatic) + catalyst | Amine-terminated polyether (D-2000, T-5000) + diamine chain extender (IPDA/MXDA) + isocyanate | Aspartic ester (diamine + diethyl maleate) + aliphatic HDI trimer/IPDI |
| Typical use | Foams, elastomers, adhesives, versatile 2K coatings | Fast plural-component linings, waterproofing, joint fill, secondary containment | Fast-return protective and architectural topcoats, concrete floors, corrosion coatings |
Sourcing the feedstock: what to buy for each chemistry
The selection logic comes down to your application equipment and your weathering requirement, and each answer points to a different shopping list.
If you need maximum versatility and a forgiving working window, build a polyurethane and pick the isocyanate by exposure: aromatic PMDI for foams and hidden layers, aliphatic HDI or IPDI for anything that faces sunlight. If you need single-pass film build at extreme thickness and humidity tolerance and you have the spray rig, build a polyurea around polyetheramine D-2000 and T-5000 with a diamine chain extender. If you want the non-yellowing performance of an aliphatic polyurea but need to brush, roll, or squeegee with a real pot life, you are formulating a polyaspartic, and the feedstock is an aspartic ester (a diamine such as IPDA or MXDA reacted with diethyl maleate) plus an aliphatic isocyanate. For the amine-resin selection within any of these, our polyetheramine (Jeffamine-equivalent) selection guide maps the D-, T-, and ED-series by backbone and function.
Honest trade-offs
There is no universally “best” chemistry; each one buys a property by spending another. Polyurea buys unmatched speed and film build, and pays for it with mandatory heated spray equipment and near-zero working time. Polyaspartic buys a tunable pot life and non-yellowing color retention, and pays for it with a higher-cost aliphatic isocyanate and a sometimes-aggressive cure that still rewards careful formulation. Polyurethane buys versatility and an easy working window, and pays for it with slower cure and, in the aromatic grades, yellowing. The right call is the one that matches your application method, your exposure, and your weathering spec, validated on your own substrate before you commit a line.
Sourcing intermediates with RawSource
RawSource supplies the raw materials and intermediates behind all three chemistries for coatings and industrial manufacturing formulators: amine-terminated polyethers (polyetheramine D-2000, T-5000), cycloaliphatic and araliphatic diamines (IPDA, MXDA), aliphatic polyisocyanates (HDI biuret, HDI isocyanurate trimer, IPDI), aromatic polymeric MDI, and the diethyl maleate (DEM) feedstock for aspartic-ester synthesis, in drums, IBCs, and bulk, with Certificate of Analysis (CoA) documentation. We supply intermediates, not finished, formulated polyaspartic-ester or phenalkamine systems. Tell us your application method, weathering target, and pot-life window, and request a sample to qualify reactivity on your own system.
*Jeffamine® is a registered trademark of Huntsman Corporation and Desmodur® is a registered trademark of Covestro; RawSource is not affiliated with, authorized, or endorsed by either; product names appear only for nominative comparison.*
Frequently asked questions
What is the difference between polyurea and polyurethane?
The difference is the reaction partner of the isocyanate. Polyurethane forms when an isocyanate (–NCO) reacts with a polyol (–OH), creating urethane linkages and curing relatively slowly with a long, catalyst-tunable pot life. Polyurea forms when an isocyanate reacts with an amine (–NH₂), creating urea linkages and curing in seconds because amines are far more reactive toward isocyanates than hydroxyls. In practice, that speed difference is why polyurea is sprayed through heated plural-component equipment while many polyurethanes can be brushed or rolled.
What is polyaspartic made of?
A polyaspartic coating is made by reacting an aliphatic polyisocyanate (HDI trimer or IPDI chemistry) with a polyaspartic ester, also called an aspartic ester resin. The aspartic ester is itself made by an aza-Michael addition of a primary diamine (commonly a cycloaliphatic or araliphatic type such as IPDA or MXDA) onto a dialkyl maleate, usually diethyl maleate (DEM). The bulky ester groups create steric hindrance around the amine, which slows the otherwise instantaneous amine–isocyanate reaction into a usable pot life.
What is the difference between polyaspartic and polyurethane?
Both can be made non-yellowing with an aliphatic isocyanate, but they react through different partners. Polyurethane crosslinks an isocyanate with a polyol (–OH); polyaspartic crosslinks an aliphatic isocyanate with an aspartic ester, which is a hindered secondary diamine, so it forms urea linkages and is technically an aliphatic polyurea. Polyaspartic typically develops handling strength and return-to-service faster than a comparable polyurethane, while a polyurethane usually offers a longer, more forgiving working window. Validate cure and adhesion on your own substrate.
Is polyaspartic the same as polyurea?
Chemically, a cured polyaspartic film is a type of aliphatic polyurea, because the aspartic ester is an amine and the linkage formed is a urea group. The practical difference is speed and equipment. Conventional “pure” polyurea reacts in seconds and requires heated plural-component spray; polyaspartic uses a sterically hindered aspartic ester to slow that reaction to a pot life of roughly 15–40 minutes, so it can be brushed, rolled, or squeegeed.
What is diethyl maleate used for in this chemistry?
Diethyl maleate (DEM) is the dialkyl maleate feedstock used to manufacture aspartic esters. A primary diamine adds across the activated carbon–carbon double bond of the maleate in an aza-Michael reaction, converting the primary amine to a hindered secondary amine and building the aspartic ester backbone. That ester is then the amine-functional half of a polyaspartic (aliphatic polyurea) coating. RawSource supplies DEM as a feedstock; we do not supply the finished aspartic-ester resin.
Which raw materials does RawSource supply for these systems?
RawSource supplies the intermediates, not finished formulated systems: amine-terminated polyethers (polyetheramine D-2000, T-5000), cycloaliphatic and araliphatic diamines (IPDA, MXDA), aliphatic polyisocyanates (HDI biuret, HDI isocyanurate trimer, IPDI), aromatic polymeric MDI, and diethyl maleate as the aspartic-ester feedstock. We do not sell finished polyaspartic-ester resins or phenalkamine. Tell us your application method and weathering target and request a sample to qualify reactivity on your own system.
Editorial note. This article is general technical guidance for coatings and industrial formulation and procurement professionals. Reaction speed, pot life, cure, weatherability, and final film performance depend on your specific isocyanate, polyol or amine, ratio, catalyst, film build, substrate, and cure conditions, and must be validated on your own system; the Certificate of Analysis (CoA) governs the grade you buy. Isocyanates are respiratory sensitizers and diisocyanates are a recognized cause of occupational asthma: use local exhaust ventilation, supplied-air respirators for spray application, and skin and eye protection, and review the current Safety Data Sheet (SDS) and applicable occupational-exposure limits before handling, storage, transport, or disposal. RawSource supplies raw materials and intermediates, not finished coating systems. Products are sold for industrial and professional use only. Nothing here is a medical, health, safety, or efficacy claim, and brand names appear only as nominative comparisons (see the trademark attribution above). RawSource makes no warranty, express or implied, and assumes no liability for use of this information.
