1K, 2K, Waterborne, Moisture-Curing, and Blocked Systems: Classification Logic and Identification Methods for Polyurethane Coating Curing Systems

Introduction

In polyurethane coatings, terms such as “1K, 2K, waterborne, moisture-curing, and blocked systems” are often compared side by side, but they do not belong to the same classification dimension. 1K and 2K describe packaging and application method; waterborne, solventborne, and solvent-free describe the dispersion medium or system form; moisture-curing, baking-curing, and blocked isocyanate systems describe the curing trigger or latent reaction mechanism.

To identify the curing system of a polyurethane coating, several questions should be answered in sequence:

Key Question	Corresponding Dimension
Do two components need to be mixed before application?	Determines 1K / 2K
In what medium are the resin or curing agent mainly dispersed?	Determines waterborne / solventborne / solvent-free
Does film formation mainly rely on physical drying or chemical reaction?	Determines the film-forming and curing mechanism
What condition triggers curing?	Determines room-temperature reaction / moisture-curing / thermal deblocking / self-crosslinking
What establishes the final performance?	Determines the contribution of resin properties, crosslink density, and curing completeness

The transformation of polyurethane coatings from a liquid or dispersed state into a continuous film usually involves solvent or water evaporation, particle coalescence, reactive crosslinking, and related processes. The final performance of the coating film largely depends on whether the drying and curing processes are sufficiently completed.

1. Start with the Classification Dimension: 1K/2K, Waterborne, and Moisture-Curing Are Not the Same Type of Concept

To understand polyurethane coating curing systems, the first basic point is to distinguish what 1K and 2K actually mean: they refer to whether two components need to be mixed before application.

Name	Meaning	Is Pre-Application Mixing Required?	Typical Description
1K polyurethane	One-component polyurethane system	No on-site mixing of two components is required	The coating is supplied as a single-package system. After application, it may form a film or cure through water evaporation, moisture reaction, self-crosslinking, oxidative drying, or thermal deblocking.
2K polyurethane	Two-component polyurethane system	Two components must be mixed in a specified ratio before application	Typically consists of Component A resin and Component B polyisocyanate curing agent. After mixing, chemical crosslinking occurs.

1K indicates a single-package system, while 2K indicates a two-package system. They cannot be directly equated with waterborne, solventborne, moisture-curing, or baking-curing systems.

To avoid confusion, common names of polyurethane coatings can be divided into three dimensions:

Classification Dimension	Specific Terms	Main Question Answered by This Dimension
Packaging and application method	1K, 2K	Whether two components must be mixed before application
Dispersion medium or system form	Waterborne, solventborne, solvent-free, high-solids	In what medium the resin or crosslinking component mainly exists
Curing trigger	Room-temperature reaction, moisture-curing, baking-curing, blocked curing, self-crosslinking	What condition triggers film formation or crosslinking

The following table makes this clearer:

Practical Term	Correct Interpretation
Waterborne 1K polyurethane	Waterborne medium + single-package system
Waterborne 2K polyurethane	Waterborne medium + two-component system that crosslinks after mixing
Solventborne 2K polyurethane	Solventborne medium + two-component system that crosslinks after mixing
1K moisture-curing polyurethane	Single-package system + curing triggered by moisture from air or substrate
1K blocked isocyanate system	Single-package system + crosslinking after thermal deblocking
Baking-curing polyurethane	Curing is promoted or triggered by heating; it may be a blocked isocyanate system or another thermosetting system

2. Distinguishing Film Formation from Curing: Surface Dry Does Not Mean Fully Cured

In coatings, “film formation” and “curing” often occur simultaneously, but they have different meanings.

2.1 Film Formation

Film formation refers to the process in which a coating changes from a liquid, dispersed, or molten state into a continuous coating film. Common film-forming mechanisms include:

Film-Forming Method	Typical Systems
Solvent evaporation	Solventborne coatings
Water evaporation	Waterborne coatings
Polymer particle coalescence	Waterborne polyurethane dispersions, acrylic emulsions
Cooling after melt flow and leveling	Powder coatings, hot-melt systems
Formation of a continuous network after reaction	Reactive polyurethane, epoxy, polyurea, and related systems

2.2 Curing

Curing refers to chemical reactions occurring inside the coating film, causing molecular chain extension, branching, or crosslinking, thereby improving film strength, water resistance, solvent resistance, chemical resistance, and durability. Common curing reactions in polyurethane coatings include:

Curing Reaction	Typical Systems
Reaction between isocyanate groups and hydroxyl groups	2K polyurethane, baking-curing polyurethane
Reaction between isocyanate groups and amine groups	Polyurea or polyurethane-polyurea systems
Reaction between isocyanate groups and moisture	Moisture-curing polyurethane
Thermal deblocking of blocked isocyanates followed by reaction	Blocked isocyanate systems
Self-crosslinking or external crosslinking after film formation	Self-crosslinking PUD, waterborne 2K polyurethane, etc.

“Dry” should not be simply equated with “fully cured.” Some coating films become surface-dry very quickly, while internal reactions continue. In some waterborne films, even after water has evaporated, water resistance, solvent resistance, and chemical resistance may still need to develop gradually through subsequent crosslinking or conditioning.

3. 2K Polyurethane: Mixed Before Application, Then Crosslinked by Reaction

2K is a common abbreviation for two-component systems in the coatings industry. Its core meaning is that two components must be mixed in a specified ratio before application. A typical 2K polyurethane coating consists of two components:

Component	Typical Composition
Component A	Hydroxyl-containing resin, polyester polyol, acrylic polyol, polyurethane polyol, or other active-hydrogen-containing components
Component B	Polyisocyanate curing agent, such as HDI trimer, HDI biuret, IPDI derivatives, etc.

After the two components are mixed in the prescribed ratio before application, isocyanate groups react with hydroxyl groups, amine groups, or other active-hydrogen-containing groups to form a crosslinked coating film. In typical 2K PU coatings, the NCO–OH reaction is the main reaction, but in a broader sense, active-hydrogen-containing components are not limited to hydroxyl groups.

3.1 Main Characteristics of 2K Polyurethane

Item	Characteristics
Packaging form	Two components stored separately
Application method	Mixed in a specified ratio before use
Curing mechanism	Chemical crosslinking occurs after mixing
Application limitation	Pot life exists after mixing
Performance characteristics	Generally higher crosslinking degree and higher potential performance ceiling
Key control points	Mixing ratio accuracy, mixing uniformity, application temperature and humidity, pot life, film thickness, and curing/conditioning conditions

3.2 Common Misunderstandings About 2K Polyurethane

① 2K does not mean solventborne.

2K only indicates two-component packaging and pre-application mixing. It does not mean the system must be solventborne. Waterborne 2K polyurethane systems also exist.

② 2K does not mean immediate full curing at room temperature.

A 2K polyurethane begins reacting after mixing, but full curing usually requires a certain amount of time. Surface dry, through dry, and final performance development are not completely synchronized.

③ 2K does not necessarily mean the best performance.

2K systems usually have high performance potential, but final performance still depends on resin structure, curing agent type, NCO/OH equivalent ratio, application conditions, and curing completeness.

4. 1K Polyurethane: Single-Package, but Not Limited to One Curing Mechanism

1K is a common abbreviation for one-component systems in the coatings industry. Its core meaning is that the resin and curing agent do not need to be mixed separately before application. However, 1K polyurethane does not represent one fixed curing mechanism. It may be a physically drying system, a moisture-curing system, a self-crosslinking system, an oxidative-drying system, or a blocked isocyanate baking-curing system.

Type of 1K Polyurethane	Film-Forming or Curing Mechanism	Main Characteristics
Physically drying PUD	Film formation by particle coalescence after water evaporation	Easy to use, wide application window, performance mainly depends on the resin itself
Self-crosslinking PUD	Internal crosslinking occurs after film formation	Single-package system; performance can continue to improve after film formation
Moisture-curing polyurethane	Active NCO reacts with moisture from air or substrate	Single-package system; depends on humidity and moisture diffusion
Blocked isocyanate system	Participates in crosslinking after thermal deblocking	Stable during storage at room temperature; usually requires baking
Oxidative-drying PU or PU-modified system	Unsaturated structures undergo oxidative crosslinking with oxygen in air	Suitable for some 1K waterborne PU or PU-modified systems containing unsaturated structures; conventional PUDs generally do not rely on oxidative drying as the main film-forming or curing mechanism

When evaluating a 1K PU system, it is still necessary to determine whether it is physically drying, moisture-curing, latently crosslinking, or thermally deblocked. All of these systems can be 1K, but their curing mechanisms, application control points, and final performance development are completely different.

5. Waterborne Polyurethane: “Waterborne” Describes the Medium, Not the Curing Mechanism

In waterborne polyurethane, the term “waterborne” means that water is used as the main dispersion medium, dilution medium, or continuous phase. It answers the question “in what medium does the system mainly exist,” rather than “how does the coating film cure.” Common forms of waterborne polyurethane include:

Type	Description
Waterborne polyurethane dispersion	Commonly referred to as PUD, meaning polyurethane dispersion
Waterborne 1K polyurethane coating	Usually does not require an externally added curing agent before application
Waterborne 2K polyurethane coating	A water-dispersible or hydrophilically modified polyisocyanate curing agent is added before use
Waterborne blocked isocyanate system	Relatively stable at room temperature; undergoes deblocking and crosslinking after heating
Waterborne polyurethane hybrid system	Such as PU/acrylic, PU/epoxy, PU/silicone, and other hybrid systems

PUDs typically form continuous films through water evaporation, particle approach, particle deformation, and coalescence. If the system contains self-crosslinking structures or an external crosslinker, further crosslinking may occur after film formation.

Waterborne systems are generally helpful in reducing VOCs and odor, but “waterborne” does not mean “VOC-free.” The actual VOC level still depends on cosolvents, coalescing agents, amine neutralizers, wetting and dispersing agents, and the overall formulation design.

5.1 Waterborne 1K Polyurethane

Waterborne 1K polyurethane is usually based on PUD and does not require the addition of an external curing agent before application. Its typical film-forming process is as follows:

Stage	Process
1	Water evaporation
2	Dispersed particles gradually approach each other
3	Particles deform and coalesce
4	A continuous film forms
5	Self-crosslinking or post-crosslinking occurs if required

The advantages of waterborne 1K polyurethane include convenient application, low odor, and fewer pot-life restrictions. It is suitable for systems requiring application convenience, environmental friendliness, and on-site operational stability. However, the final performance of waterborne 1K polyurethane should not be evaluated only by surface-drying speed. Resin structure, soft/hard segment design, minimum film-forming temperature, drying conditions, conditioning time, and the presence or absence of a self-crosslinking mechanism should also be considered.

5.2 Waterborne 2K Polyurethane

Waterborne 2K polyurethane is usually composed of a waterborne hydroxyl-containing resin or dispersion and a water-dispersible or hydrophilically modified polyisocyanate curing agent. The two components are mixed before application, and crosslinking occurs in the waterborne environment after mixing. The key challenge of waterborne 2K polyurethane lies in balancing the reaction and film-forming processes.

Key Issue	Description
Dispersibility of curing agent	The polyisocyanate must be sufficiently dispersed in the waterborne system
Competing reactions	The NCO–OH reaction and the NCO–water reaction occur competitively
Pot life	After mixing, system viscosity, reaction degree, and application properties change over time
Matching of drying and crosslinking	Water evaporation, particle coalescence, and chemical crosslinking must be coordinated
Early water resistance	If initial drying is insufficient or crosslinking is incomplete, early water resistance may be weak
Final performance	Depends on crosslink density, curing completeness, and conditioning conditions

6. Moisture-Curing Polyurethane: Reaction Involving Moisture from Air or Substrate

Moisture-curing polyurethane is usually a one-component system. It is commonly based on polyurethane prepolymers terminated with active NCO groups. After application, the NCO groups react with moisture from the air or substrate, further forming a cured coating film. The basic process of moisture curing is as follows:

Stage	Reaction Process
1	Water molecules attack isocyanate groups, forming unstable carbamic acid
2	Carbamic acid decomposes to form amine and carbon dioxide
3	The amine further reacts with isocyanate to form urea linkages
4	Under conditions such as excess NCO, catalysis, or elevated temperature, urea linkages may further react with NCO to form biuret structures and increase the degree of crosslinking

This reaction mechanism is the key distinction between moisture-curing polyurethane and ordinary physically drying systems.

6.1 Main Characteristics of Moisture-Curing Polyurethane

Item	Characteristics
Packaging form	Usually 1K
Triggering condition	Moisture from air or substrate
Main reaction	NCO reacts with water, further forming urea linkages and crosslinked structures
Advantage	Single-package system; no mixing required before application
Limitations	Strongly affected by humidity, film thickness, ventilation, temperature, and substrate moisture content
Risks	CO₂ is generated during the reaction; thick films or improper moisture control may cause bubbles, pinholes, or insufficient internal curing

Moisture-curing polyurethane does not simply form a film by solvent evaporation. Its curing quality depends on whether moisture can enter the coating film, whether NCO groups can react sufficiently, whether CO₂ can escape smoothly, and whether film thickness and environmental humidity are appropriate. Therefore, a moisture-curing system should not be judged only by surface-drying speed; sufficient internal curing must also be considered.

7. Blocked Isocyanate Systems: Stable at Room Temperature, Reactive After Heating

A blocked isocyanate temporarily “protects” isocyanate groups with a blocking agent, making them relatively stable toward hydroxyl groups, water, and other active-hydrogen-containing components at room temperature. When the temperature rises to a certain range, the blocked structure undergoes deblocking or regenerates reactive NCO groups, which then react with hydroxyl groups, amine groups, or other active-hydrogen-containing components to form a crosslinked network. The curing process of a blocked isocyanate system can be summarized as follows:

Stage	Process
Room-temperature storage stage	NCO is blocked, and the system is relatively stable
Heating stage	The blocked structure undergoes deblocking, exchange reaction, or regeneration of active NCO
Reaction stage	NCO reacts with hydroxyl groups, amine groups, or other active-hydrogen-containing components
Curing stage	A crosslinked coating film is formed

7.1 Main Characteristics of Blocked Isocyanate Systems

Item	Characteristics
Packaging method	Can be designed as a single-package system
Storage stability	Relatively stable at room temperature
Curing condition	Usually requires heating
Application characteristics	Suitable for industrial baking coating processes
Key control points	Deblocking temperature, baking temperature, baking time, catalyst, and completeness of crosslinking reaction
Limitation	Not suitable for applications where heating is unavailable or low-temperature application is required

The core value of blocked isocyanate systems is that they balance single-package storage stability with polyurethane crosslinking performance. However, they usually require baking conditions and are therefore more suitable for industrial coating systems with thermal curing capability. It should be noted that the deblocking temperature is not a fixed value; it is influenced by the type of blocking agent, isocyanate structure, catalyst, resin environment, and baking schedule.

8. Multidimensional Identification: Understanding the Actual System from the Product Name

The actual name of a polyurethane coating is usually not based on a single classification. Instead, it is composed of packaging method, medium type, and curing mechanism.

System Label	Main Dimension Described	Typical Meaning	Key Identification Point
1K	Packaging and application method	Single-package system; no mixing of two components required before application	The curing mechanism cannot be determined from 1K alone. It is still necessary to determine whether it is physically drying, moisture-curing, self-crosslinking, or thermally cured.
2K	Packaging and application method	Two-component system; must be mixed in a specified ratio before application	Typically involves the reaction of NCO with OH or other active-hydrogen-containing groups. Mixing ratio, mixing quality, pot life, and application conditions must be considered.
Waterborne	Medium type	Uses water as the main dispersion medium, dilution medium, or continuous phase	Waterborne does not indicate one specific curing mechanism. It may be 1K or 2K.
Moisture-curing	Curing trigger	Active NCO reacts with moisture from air or substrate	Humidity, film thickness, ventilation, moisture diffusion, and CO₂ release must be considered.
Blocked isocyanate	Latent reaction mechanism	NCO is blocked and relatively stable at room temperature; after heating, it deblocks and crosslinks	Deblocking temperature, baking schedule, catalyst, and crosslinking completeness must be considered.
Baking-curing	Curing process condition	Crosslinking reaction is promoted or triggered by heating	Baking-curing is not a single chemical category. It is necessary to further determine whether it is a blocked isocyanate system or another thermosetting system.

Therefore, when encountering an actual product name, the name should be broken down and understood dimension by dimension.

Name	More Accurate Interpretation
Waterborne 2K polyurethane	Waterborne medium + two-component packaging + crosslinking after mixing
1K moisture-curing polyurethane	Single-package system + NCO reaction triggered by moisture from air or substrate
Waterborne blocked isocyanate baking-curing system	Waterborne medium + blocked isocyanate + curing by thermal deblocking
1K self-crosslinking PUD (Polyurethane Dispersion)	Single-package system + film formation by water evaporation + self-crosslinking after film formation
Solventborne 2K polyurethane	Solventborne medium + two-component packaging + room-temperature reactive crosslinking

9. Steps for Identifying the Curing System of a Polyurethane Coating

To determine which type of curing system a polyurethane coating belongs to, the following sequence can be used.

Step 1: Check the Packaging Method

Identification	Conclusion
Two components need to be mixed before application	2K
No two-component mixing is required before application	1K
Only “1K” or “2K” is known	Only the application format can be identified; the curing mechanism cannot be directly determined

Step 2: Check the Dispersion Medium

Identification	Conclusion
Water is used as the main dispersion medium or diluent	Waterborne system
Organic solvent is used as the main medium	Solventborne system
The solvent content is very low or the system is essentially solvent-free	High-solids or solvent-free system; the reaction mechanism still needs to be further examined

Step 3: Check the Main Curing Trigger

Triggering Condition	Possible System
Reaction after mixing two components	2K polyurethane
Particle coalescence and film formation after water evaporation	Physically drying PUD
Further internal crosslinking after film formation	Self-crosslinking or post-crosslinking PUD
Moisture from air or substrate participates in the reaction	Moisture-curing polyurethane
Deblocking and crosslinking after heating	Blocked isocyanate system
Heating promotes the overall reaction	Baking-curing polyurethane or other thermosetting systems

Step 4: Check How Final Performance Is Established

Performance Development Mechanism	Key Points for Identification
Mainly relies on physical film formation	Resin structure, degree of particle coalescence, drying conditions
Relies on chemical crosslinking	Crosslink density, mixing ratio, reaction completeness, conditioning conditions
Relies on moisture curing	Humidity, film thickness, moisture diffusion, CO₂ release
Relies on thermal curing	Deblocking temperature, baking temperature, baking time, heat resistance of the substrate
Relies on self-crosslinking or post-crosslinking	Film-forming conditions, crosslinking trigger conditions, conditioning time

10. Representative Chemical Classification Tables for Polyurethane Coating Curing Systems： 1K, 2K, Waterborne, Moisture-Curing, Blocked Systems, and Supporting Additives

Table 1: Polyisocyanate Curing Agents for 2K Polyurethane Coatings

Category	CAS No.	Aladdin Catalog No.	Name	Specification or Purity	Product Features and Applications
2K aliphatic polyisocyanate curing agent	28182-81-2	P485967	Poly(hexamethylene diisocyanate) (PolyHDI)	Viscosity 900–1500 cP, 25 °C	Used for two-component clearcoats based on hydroxyl acrylic resins, weather-resistant coatings, and studies on crosslink density and gel time
2K aliphatic biuret-type curing agent	4035-89-6	T770979	1,3,5-Tris(6-isocyanatohexyl)biuret	NCO content: 21–22.5%	Used for two-component polyurethane topcoats, chemical-resistant coatings, and experiments on curing rate and hardness development
2K aromatic polymeric isocyanate curing agent	9016-87-9	P304914	Polymethylene polyphenyl polyisocyanate	NCO content ~30%; viscosity ~200 mPa·s, 25 °C	Used for high-solids polyurethane coatings, primers, and adhesive systems to study crosslinking reactions and bonding strength
2K aliphatic isocyanurate curing agent	3779-63-3	H694586	1,3,5-Tris(6-isocyanatohexyl)-1,3,5-triazinane-2,4,6-trione	≥95%	Used for weather-resistant polyurethane topcoats, low-yellowing clearcoats, and studies on crosslinked structures and solvent resistance

Table 2: Isocyanate Raw Materials for 1K Moisture-Curing Systems and Prepolymer Synthesis

Category	CAS No.	Aladdin Catalog No.	Name	Specification or Purity	Product Features and Applications
Aliphatic diisocyanate raw material for moisture-curing prepolymers	822-06-0	H106723	Hexamethylene diisocyanate (HDI)	Moligand™, ≥99%	Used for one-component moisture-curing prepolymers, aliphatic polyurethane resins, and studies on reaction activity in weather-resistant coatings
Cycloaliphatic diisocyanate raw material for moisture-curing prepolymers	4098-71-9	I109582	Isophorone Diisocyanate, mixture of isomers (IPDI)	≥99%	Used for waterborne polyurethane prepolymers, moisture-curing coatings, and studies on hard-segment structure and yellowing resistance
Aromatic diisocyanate raw material for moisture-curing prepolymers	26471-62-5	T135411	Tolylene Diisocyanate, 2,4- and 2,6-isomers (TDI)	≥98%, GC	Used for aromatic polyurethane prepolymers, elastic coatings, and studies on the effect of isomer composition on reaction rate
Araliphatic diisocyanate raw material for moisture-curing prepolymers	3634-83-1	M158033	m-Xylylene Diisocyanate (MXDI)	≥98%, GC	Used for transparent polyurethane coatings, chemical-resistant coatings, and studies on the effect of araliphatic structures on coating-film performance
Aromatic diisocyanate raw material for moisture-curing prepolymers	101-68-8	M106783	4,4'-MDI (MDI)	≥98%	Used for moisture-curing polyurethane prepolymers, primers, and studies on hard-segment content and mechanical properties
Aromatic diisocyanate raw material for moisture-curing prepolymers	91-08-7	T769897	Tolylene-2,6-diisocyanate	≥98%	Used for polyurethane reaction-mechanism studies, isomer reactivity research, and prepolymer end-group control experiments
Araliphatic diisocyanate raw material for moisture-curing prepolymers	2778-42-9	B152785	1,3-Bis(2-isocyanato-2-propyl)benzene	≥97%, GC	Used for low-viscosity polyurethane prepolymers, weather-resistant coatings, and studies on the effect of sterically hindered structures on curing reactions
Cycloaliphatic diisocyanate raw material for moisture-curing prepolymers	5124-30-1	D155475	Dicyclohexylmethane 4,4'-Diisocyanate, mixture of isomers (HMDI)	≥90%, GC	Used for cycloaliphatic polyurethane coatings, yellowing-resistant elastic coating films, and studies on balancing flexibility and hardness

Table 3: Hydrophilic Chain Extenders, Neutralizers, Amine Chain Extenders, and Process Solvents for Waterborne Polyurethane Systems

Category	CAS No.	Aladdin Catalog No.	Name	Specification or Purity	Product Features and Applications
Neutralizer for waterborne polyurethane	121-44-8	T140677	Triethylamine	Anhydrous grade, ≥99.5%, water ≤50 ppm	Used for neutralization and salt formation in carboxylic-acid-type waterborne polyurethane, dispersion stability, and particle-size control experiments
Cosolvent for waterborne polyurethane prepolymers	872-50-4	M119668	1-Methyl-2-pyrrolidinone (NMP)	Anhydrous grade, ≥99.5%	Used for dissolving hydrophilic chain extenders, reducing prepolymer viscosity, and improving reaction-system homogeneity before dispersion
Process solvent for the acetone process in waterborne polyurethane	67-64-1	A486158	Acetone	Natural, ≥97%	Used for prepolymer dilution in the acetone process for waterborne polyurethane, phase-transfer dispersion, and solvent-removal process experiments
Amine chain extender for waterborne polyurethane	107-15-3	E431349	Ethylenediamine	Suitable for synthesis	Used for chain extension after water dispersion, introduction of urea linkages, and control of particle size and tensile strength
Alkanolamine chain extender for waterborne polyurethane	111-42-2	D431475	Diethanolamine (DEA)	Suitable for analysis, guaranteed reagent grade	Used for polyurethane chain extension and end-group modification, hydroxyl-content adjustment, and coating adhesion studies
Neutralizer and amine catalyst for waterborne polyurethane	108-01-0	D109080	N,N-Dimethylethanolamine	Distilled grade, ≥99.5%	Used for neutralization of carboxylic-acid-type waterborne polyurethane, dispersion stability, and studies on amine-catalyzed curing rate
Neutralizer and acid-value regulator for waterborne polyurethane	124-68-5	A755868	2-Amino-2-methyl-1-propanol	BioReagent, ≥95%	Used for waterborne polyurethane neutralization, emulsion pH adjustment, and storage-stability studies
Volatile neutralizer for waterborne polyurethane	1336-21-6	A112077	Ammonia solution	Guaranteed reagent, 25–28%	Used for neutralization and salt formation in carboxylic-acid-type waterborne polyurethane dispersions, pH adjustment, emulsion dispersion stability, and coating-film water-resistance studies
Tertiary amine diol chain extender for waterborne polyurethane	105-59-9	M105603	N-Methyldiethanolamine	≥99%	Used for the structural design of cationic or salt-formable polyurethane, and for controlling hydrophilicity and adhesion
Cycloaliphatic amine chain extender for waterborne polyurethane	2855-13-2	A104545	Isophoronediamine, cis- and trans-mixture (IPDA)	≥99%	Used for post-chain extension of waterborne polyurethane, introduction of polyurea hard segments, and studies on water resistance and mechanical properties
Carboxylic-acid-type hydrophilic chain extender for waterborne polyurethane	10097-02-6	B115196	2,2-Bis(hydroxymethyl)butyric acid (DMBA)	≥98%	Used for internal emulsification of anionic waterborne polyurethane, particle-size control, and studies on film-forming water resistance
Carboxylic-acid-type hydrophilic chain extender for waterborne polyurethane	4767-03-7	B104539	2,2-Bis(hydroxymethyl)propionic acid (DMPA)	≥98%	Used for preparing anionic waterborne polyurethane dispersions, adjusting solid content, and emulsion-stability experiments

Table 4: Blocking Agents and Latent Curing Components for Blocked Polyurethane Latent-Curing Systems

Category	CAS No.	Aladdin Catalog No.	Name	Specification or Purity	Product Features and Applications
Lactam blocking agent for blocked polyurethane	105-60-2	C111698	Caprolactam	Chemically pure, CP	Used for preparing blocked isocyanates, baking-curing coatings, and studies on deblocking temperature and storage stability
Phenolic blocking agent for blocked polyurethane	108-95-2	P100761	Phenol	Standard for GC, ≥99.5%	Used for model reactions of phenol-blocked isocyanates, thermal deblocking behavior, and latent curing kinetics experiments
Pyrazole blocking agent for blocked polyurethane	67-51-6	D139167	3,5-Dimethylpyrazole	≥99%	Used for low-temperature deblocking isocyanate blocking, powder coatings, and baking-coating reaction studies
Oxime blocking agent for blocked polyurethane	96-29-7	B105233	2-Butanone oxime	≥99%	Used for preparing oxime-blocked isocyanates, one-component baking coatings, and studies on latent reaction activity
Active-methylene blocking agent for blocked polyurethane	105-53-3	D103949	Diethyl malonate	≥99%	Used for active-methylene-blocked isocyanates, low-temperature curing exploration, and studies on deblocking reaction mechanisms
Blocked/latent polyurethane uretdione-type isocyanate component	23501-81-7	B1234624	1,3-Bis(6-isocyanatohexyl)-1,3-diazetidine-2,4-dione	_	Used for studies on HDI uretdione/latent NCO structures, thermal deblocking or ring-opening reactions, thermally cured coatings, and curing windows

Table 5: Polyurethane Curing Catalysts, Accelerators, Coalescing Agents, and Formulation Additives

Category	CAS No.	Aladdin Catalog No.	Name	Specification or Purity	Product Features and Applications
Tertiary amine catalyst for polyurethane	280-57-9	T105635	1,4-Diazabicyclo[2.2.2]octane (DABCO, triethylenediamine)	Moligand™, ≥98%	Used for catalyzing the reaction between isocyanate and hydroxyl groups, and for comparative experiments on foaming and coating curing rates
Metal carboxylate catalyst for polyurethane	136-53-8	Z283372	Zinc 2-ethylhexanoate	ca. 80% in mineral spirits, 17–19% Zn	Used for polyurethane crosslinking catalysis, promotion of blocked-isocyanate deblocking, and studies on coating-film drying performance
Bismuth catalyst for polyurethane	34364-26-6	B283250	Bismuth(III) neodecanoate	≥99.9% metals basis, 60% in neodecanoic acid, 15–20% Bi	Used for low-tin polyurethane catalyst systems, curing of two-component coatings, and studies on pot life and surface-drying time
Strong basic amine catalyst for polyurethane	6674-22-2	D106478	1,8-Diazabicyclo[5.4.0]undec-7-ene (DBU)	≥99%	Used for promoting deblocking of blocked isocyanates, catalyzing urethane-forming reactions, and low-temperature curing experiments
Coalescing agent for waterborne polyurethane	25265-77-4	T103778	2,2,4-Trimethyl-1,3-pentanediol 1-monoisobutyrate	≥99%	Used for film formation in waterborne polyurethane coatings, leveling adjustment, and studies on low-temperature film-forming performance
Coalescing and leveling cosolvent for waterborne polyurethane	29911-28-2	D133306	Dipropylene glycol butyl ether (DPNB)	≥98%, mixture of isomers	Used for cosolvency in waterborne polyurethane coatings, adjustment of open time, and application leveling experiments
Cosolvent and film-formation regulator for waterborne polyurethane	34590-94-8	D108833	Di(propylene glycol) methyl ether, mixture of isomers	≥98%	Used for cosolvency in waterborne polyurethane dispersions, viscosity adjustment, and studies on the film-forming process
Organotin catalyst for polyurethane	77-58-7	D100274	Dibutyltin dilaurate (DBTDL)	≥95%	Used for catalyzing the reaction between isocyanate and hydroxyl groups, curing kinetics of two-component coatings, and pot-life studies
Stannous catalyst for polyurethane	301-10-0	T100108	Tin 2-ethylhexanoate	≥95%	Used for polyurethane prepolymer synthesis, catalysis of moisture-curing systems, and studies on gel time and hardness development

Note: The above are representative products from Aladdin. For more product specifications, search by “product name / CAS / catalog number” on the Aladdin official website.

References

[1] Zubair, Z., Shaker, K., & Hafeez, A. Curing and Drying Processes. In: Functional Polyurethane Coatings: Formulations, Properties, and Applications. SpringerBriefs in Materials, Springer, 2026.

[2] SpecialChem. Polyurethane Coatings: How to Formulate Them?

[3] Covestro. Bayhydrol® | PU Dispersions.

[4] Nakao, M. 1K PUR Dispersion with Comparable Performance to 2K Waterborne Coating. American Coatings Association, CoatingsTech Magazine.

[5] Zhou, J.; Liu, Z.; Zhu, Z.; Zeng, Z.; Sun, L. The kinetics of the polyurethane moisture curing reaction: a combined experimental and DFT mechanistic study. Reaction Chemistry & Engineering. First published 30 Sep 2024.

[6] Rolph, M. S., Markowska, A. L. J., Warriner, C. N., & O’Reilly, R. K. Blocked isocyanates: from analytical and experimental considerations to non-polyurethane applications. Polymer Chemistry, 2016.

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