Waterborne acrylic, waterborne polyurethane, and other resin systems have been widely used in coatings, inks, leather, surface treatment, and other fields thanks to their low VOC emissions, safe application, and other advantages.
However, as application requirements continue to rise, relying solely on the resin itself may still result in insufficient water, solvent, and abrasion resistance. Forming a network structure between a crosslinker and a polymer is an important way to improve the overall performance of waterborne systems.
How should you choose between carbodiimides and blocked isocyanates for different resin functional groups and curing conditions?
To address different resin structures and application conditions, Langyi New Materials has introduced the HyMax® CA waterborne carbodiimide crosslinker and the HyMax® WBI waterborne blocked isocyanate curing agent, , providing two complementary crosslinking technology routes for waterborne systems.
Both can improve water resistance, chemical resistance, abrasion resistance, and adhesion, but they differ in reactive targets, curing temperatures, and optimal application windows.
01
CROSSLINKING BASICS
Essentially, a crosslinker creates more chemical bonds between polymer molecular chains, enabling formerly independent molecules to form a stable three-dimensional network structure.
Crosslinked materials typically offer:
Water and Solvent Resistance
Improved water resistance and better solvent resistance.
Mechanical and Interfacial Performance
Better abrasion resistance and stronger adhesion.
Long-Term Stability
Higher coating strength and long-term stability.
Therefore, in high-performance waterborne systems, crosslinkers have become an indispensable component.
02
CARBODIIMIDE
HyMax® CA is a non-toxic, environmentally friendly waterborne crosslinker containing carbodiimide functional groups. Its —N=C=N— groups react with carboxyl groups (—COOH) in polymer chains to form a stable crosslinked polymer network.
Because carbodiimide groups are highly reactive with carboxyl groups, HyMax® CA can cure polymers under relatively mild conditions, making it suitable for carboxyl-functional waterborne acrylic, waterborne polyurethane, and other resin systems.
— Curing Mechanism Between HyMax® CA Carbodiimide Groups and Carboxyl Groups
Application and Environmental Features
Non-toxic, zero VOC, low viscosity, no dilution required, and insensitive to moisture, with the advantages of easy addition and dispersion and an extra-long pot life, making it better suited to continuous production and waterborne formulations that require a long application window.
Performance Enhancements
Crosslinked coatings can achieve better water resistance, chemical resistance, abrasion resistance, and adhesion, while also improving hydrolysis resistance.
— Overview of HyMax® CA Product Features
03
BLOCKED ISOCYANATE
HyMax® WBI is a low-toxicity, environmentally friendly waterborne blocked isocyanate curing agent. Its key difference from conventional free isocyanates is that the active NCO groups are temporarily blocked, allowing the system to maintain low VOC emissions and a long pot life.
When the temperature exceeds the deblocking temperature, the system releases NCO groups that crosslink with hydroxyl, amino, and carboxyl groups, thereby improving water resistance, chemical resistance, abrasion resistance, and adhesion.
— Features of HyMax® WBI Blocked Isocyanate Curing Agents
What Does the Blocked Route Solve Compared with Conventional Isocyanates?
The blocked structure converts an "immediate reaction" into a "temperature-triggered reaction." While retaining the isocyanate's high crosslinking capability, it provides high deblocking efficiency and a longer processing window. This is a more targeted technology route for waterborne systems that can be baked and require both high crosslinking density and production stability.
04
TECHNOLOGY COMPARISON
| Selection Dimension | HyMax® CA | HyMax® WBI |
|---|---|---|
| Ingredient | Carbodiimide | Blocked Isocyanate |
| Primary Reactive Groups | Carboxyl groups in the resin | Reacts with hydroxyl, amino, and carboxyl groups after deblocking |
| Reaction Trigger | Mild conditions; temperatures above 80°C are recommended | Deblocks at 105–110°C; temperatures above 120°C are recommended |
| Application Benefits | Extra-long pot life; insensitive to moisture | Stable blocking; long pot life |
| Environmental Profile | Non-toxic; zero VOC | Low toxicity; low VOC |
| Performance Focus | Water resistance, chemical resistance, abrasion resistance, adhesion, and hydrolysis resistance | High crosslinking, water resistance, chemical resistance, abrasion resistance, and adhesion |
Choose CA first when carboxyl groups are the resin's primary reactive sites and mild curing, zero VOC, moisture insensitivity, and improved hydrolysis resistance are priorities.
Choose WBI first when the resin contains hydroxyl or amino groups, the production line can bake above 120°C, and a long pot life with heat-activated high crosslinking performance is required.
Neither route is inherently superior, nor are they simple substitutes for one another. Selection should begin by confirming the resin functional groups, ionic type, and target performance, followed by formulation trials to determine the final grade and dosage.
05
PRODUCT SOLUTIONS
HyMax® CA is applied to surface treatment, leather, inks, and coatings. Surface treatment applications include textiles, metals and coil stock, and plastic films; coating applications include furniture coatings, anticorrosive metal coatings, architectural coatings, and industrial coatings.
— Typical HyMax® CA Application Areas
HyMax® WBI: Match by Resin Ionic Type
The WBI series is primarily designed for waterborne resin systems containing —OH and —NH₂ groups. All three products offer low VOC emissions, high crosslinking, high deblocking efficiency, and a long pot life. Grade selection depends mainly on the system's ionic type, solids content, NCO content, and deblocking temperature.
∞
THE END
Selecting a waterborne crosslinker is fundamentally about matching the crosslinking reaction to the actual system. The two crosslinker solutions are designed for different functional groups, curing windows, and performance targets, forming complementary crosslinking solutions.
HyMax® CA is based on the reaction between carbodiimide and carboxyl groups, providing carboxyl-functional resins with a crosslinking solution that offers relatively mild curing conditions, zero VOC, and moisture insensitivity;
HyMax® WBI releases active NCO groups in response to temperature, providing hydroxyl-functional, amino-functional, and other compatible systems with a solution that balances the application window and curing performance.
From technology routes to specific grades, Langyi New Materials will continue to improve its portfolio of waterborne curing agents and provide professional, efficient, and environmentally friendly crosslinking solutions for surface treatment, leather, inks, coatings, and more waterborne resin applications.
