3 Types of Waterbased Resins and Film Formation Mechanism
Water-Based Resins in Coatings: Types, Film Formation, and Crosslinker Selection
Updated: 2026
Quick Answer: Water-based resins are polymer binders dissolved, dispersed, or emulsified in water for coatings, inks, adhesives, and surface-treatment systems. In coating formulation, film formation depends on water evaporation, particle packing, particle coalescence, and final polymer-chain interdiffusion; when water resistance, chemical resistance, adhesion, or heat resistance is not enough, a suitable crosslinker or curing agent is usually required.
Need help choosing a crosslinker for a water-based resin system? Share your resin type, hydroxyl value, pH, co-solvent package, curing condition, and target application. Dongsen can help screen a suitable waterbased polyisocyanate or blocked isocyanate direction.
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Water-based resins are widely used because they help formulators reduce solvent reliance while keeping practical application properties such as coating flow, film formation, adhesion, and appearance. However, a water-based resin alone does not automatically guarantee strong water resistance, solvent resistance, or chemical resistance. The final performance depends on resin chemistry, particle size, Tg, coalescent selection, drying condition, substrate, and whether the system is properly crosslinked.
This article reorganizes the basic concept of water-based resins into a practical coating-formulation guide. It explains the main resin types, the film-formation process, and how to connect the resin system with Dongsen curing-agent and crosslinker options.
What are water-based resins?
Water-based resins are polymer materials that use water as the main medium. Depending on the resin design, the polymer can be truly dissolved in water, dispersed as fine particles, or emulsified into larger latex particles. In coatings, the resin acts as the main film-forming binder, while additives, pigments, fillers, coalescents, and crosslinkers help adjust application and final film performance.
A more accurate way to describe water-based systems is lower solvent content, not “zero VOC” by default. Many water-based coatings may still contain co-solvents, neutralizing agents, or film-forming aids. For procurement and technical evaluation, the right question is not only “Is it water-based?” but also “Can the dried film meet the required water resistance, chemical resistance, adhesion, and durability?”
Which types of water-based resins are used in coatings?
| Resin type | Typical state in water | Film and performance tendency | Formulation risk to check |
|---|---|---|---|
| Water-soluble resins | Polymer chains are dissolved or partly dissolved in water, often with hydrophilic groups. | Can give good appearance and easy processing, but lower molecular weight or high hydrophilicity may limit water and solvent resistance. | High viscosity, lower water resistance, sensitivity to pH and electrolyte. |
| Water-dispersible resins | Fine polymer particles are dispersed in water, often transparent to translucent. | Can form dense films with good gloss, transparency, and improved resistance after curing. | Dispersion stability, co-solvent compatibility, and crosslinker dispersion quality. |
| Water-emulsion resins | Larger latex particles are emulsified in water and usually appear milky white. | Higher molecular weight can support mechanical strength, drying, and corrosion resistance after film formation. | Emulsifier residue, water sensitivity, particle coalescence at low temperature. |
Takeaway: Water-soluble resins are easier to process but often need help with resistance; water-dispersible and emulsion resins depend more on particle packing, coalescence, and crosslinking to reach final film performance.
How do water-based resins form a continuous film?
In a water-based coating, the film does not simply “dry” like a solvent varnish. The dispersed or emulsified polymer particles must move from a wet, separated state to a continuous film. The process usually includes three practical stages.
1. What happens when water starts to evaporate?
After application, water evaporates from the wet coating. Polymer particles, pigments, and fillers move closer together as the liquid volume decreases. At this stage, the particles are still mostly mobile, and the coating remains sensitive to airflow, temperature, humidity, and substrate absorption.
2. Why is particle coalescence the key film-forming step?
As water continues to leave, capillary pressure pushes polymer particles into closer contact. If the resin particle is soft enough under the application temperature, the particles deform and fuse into a continuous film. If the resin Tg is too high or the temperature is too low, the particles may not coalesce well, causing poor film integrity, weak gloss, cracking, or lower resistance.
3. When does crosslinking become important?
After the initial continuous film forms, polymer chain segments continue to interdiffuse and entangle. In crosslinkable systems, reactive groups can further build a stronger network. This is where a suitable crosslinker can improve water resistance, solvent resistance, chemical resistance, adhesion, hardness, or heat resistance.
Waterborne resin film formation from evaporation to particle coalescence
Why do water-based coatings still need crosslinkers?
Water-based resin selection solves only part of the formulation problem. In many industrial, wood, leather, textile, ink, and adhesive systems, the dried film must also resist water, alcohol, cleaning agents, blocking, abrasion, or heat. Crosslinkers help convert a simple thermoplastic film into a more durable network.
Product boundary: Dongsen supplies curing agents and crosslinkers as raw materials. Dongsen does not supply finished paints, finished coatings, or water-based resin binders. Dongsen crosslinkers can be used by coating and adhesive manufacturers to formulate water-based or baking coating systems.
Which Dongsen crosslinker direction fits a water-based resin system?
| Formulation situation | Main performance target | Dongsen direction | Example grade direction | Selection note |
|---|---|---|---|---|
| 2K waterborne wood, industrial, or PU coating | Improve water resistance, chemical resistance, adhesion, and film strength | Waterbased polyisocyanate, HDI-based | WD-8780/8980, WD-8100A, WD-8300 | Check resin compatibility, pH, co-solvent, mixing order, pot life, and target NCO/OH ratio. |
| 1K water-based baking coating | Improve storage stability before baking and release NCO during heating | Water-based blocked polyisocyanate | BI-70C/D/E, BI-35C/D/E, BY/HBY series | Select by ionic type, solid content, deblocking temperature, and baking window. |
| Waterborne formulation needs water as medium plus moisture reaction | Water-dispersible crosslinking support | Water-dispersive moisture-curing polyisocyanate | WDC-80H | Check application method, dispersion stability, and final use requirement before scale-up. |
| Resin film has good appearance but poor resistance | Upgrade film network after drying or baking | Reactive crosslinker screening | WD or BI direction depending on 2K vs 1K process | Do not choose by resin name only; test with the actual resin, additives, pH, and curing condition. |
Takeaway: For room-temperature 2K waterborne coatings, the WD series is usually the first direction to screen. For 1K baking systems, water-based blocked polyisocyanates are more suitable because the NCO groups are released during baking.
Dongsen grade examples for waterborne coating formulators
All values below are typical reference data and are subject to the current TDS/COA for each grade.
| Dongsen grade | Product direction | Solid % | NCO / valid NCO % | Free monomer / free NCO | Viscosity (cps) | Best-fit formulation direction |
|---|---|---|---|---|---|---|
| WD-8780/8980 | Waterbased polyisocyanate, HDI-based | 80.0±2.0 | 15.0±1 | ≤0.3 | 300±200 | Waterborne coatings where lower viscosity and practical dispersion are required. |
| WD-8100A | Waterbased polyisocyanate | 100 | 20.5±0.5 | ≤0.3 | 4500±1000 | High-solids crosslinker direction for selected waterborne systems after compatibility testing. |
| WD-8300 | Waterbased polyisocyanate | 100 | 21.8±0.5 | ≤0.3 | 2500±1000 | Waterborne systems needing strong crosslinking contribution and grade screening. |
| BI-70D | Anionic water-dispersible blocked polyisocyanate | 70 | 7.2±0.5 | ≤0.2 | 4000±1500 | 1K baking systems requiring 130–140°C deblocking direction. |
| BI-35D | Anionic water-soluble blocked polyisocyanate | 35 | 3.6±0.5 | ≤0.2 | 2500±500 | Water-medium 1K baking systems where lower solid water-soluble direction fits the formulation. |
| WDC-80H | Water-dispersive moisture-curing polyisocyanate | 80±2 | 9.0±0.5 | HDI≤0.5 | 3000±1000 | Water-dispersive crosslinking direction; confirm stability and application window by test. |
Parameter summary: WD-8780/8980 is an 80.0±2.0% solids waterbased polyisocyanate with 15.0±1% NCO and 300±200 cps viscosity; BI-70D is a 70% solids anionic water-dispersible blocked polyisocyanate with 7.2±0.5% valid NCO and a 130–140°C deblocking direction. In buyer terms: the low 300±200 cps viscosity of WD-8780/8980 means easier dispersion and handling in 2K waterborne mixing, while BI-70D's 130–140°C deblocking window means it stays stable in 1K storage and only reacts during a mid-range bake — useful for heat-tolerant metal, coil, and textile substrates. These numbers help formulators compare reactive content, viscosity, and process fit before requesting samples.
Waterbased polyisocyanate crosslinker selection for coating formulators
How should formulators choose between 2K waterborne and 1K baking systems?
| Question | 2K waterborne crosslinker direction | 1K blocked crosslinker direction |
|---|---|---|
| How does the coating cure? | Reactive crosslinker is mixed before application and reacts during drying/curing. | Blocked NCO remains stable in storage and reacts after baking at the required temperature. |
| What should you check first? | Pot life, pH stability, resin compatibility, dispersion, and NCO/OH ratio. | Deblocking temperature, baking time, substrate heat tolerance, and hydroxyl functionality. |
| Where is it often used? | Waterborne wood coatings, industrial coatings, leather finishing, and adhesive modification. | 1K baking coatings, metal coating, textile coating, printing paste, passivation, and related heat-curing systems. |
| Main risk | Poor mixing can cause particles, haze, viscosity rise, or shortened pot life. | Wrong baking window can lead to under-curing or poor final resistance. |
Takeaway: Choose 2K waterborne polyisocyanate when the customer can mix before use and needs room-temperature or low-temperature curing. Choose water-based blocked polyisocyanate when storage stability and baking activation are more important.
What should be checked before asking for a suitable grade?
To avoid selecting a crosslinker only by product name, provide the following information when requesting a grade recommendation:
- Resin type, hydroxyl value, solid content, pH, and ionic character if available.
- Application field: wood coating, industrial coating, leather surface treatment, textile coating, ink, adhesive, or other system.
- Target film issue: water resistance, alcohol resistance, adhesion, hardness, blocking resistance, flexibility, or heat resistance.
- Process: 2K room-temperature system, low-temperature drying, or 1K baking system.
- Co-solvent package, dilution method, pigment/filler load, and required pot life.
Application note: why particles may appear after adding a waterborne crosslinker
In one anonymized waterborne coating project for Southeast Asian export, a black waterborne topcoat for high-end synthetic leather showed visible particles after the crosslinker was added. The formulation was not simply a “bad resin” or “bad hardener” case. The more useful lesson was compatibility: resin hydrophilicity, crosslinker dispersion, pH, mixing order, and co-solvent balance all affected the final spray appearance. After switching to a more hydrophilic anionic waterborne crosslinker direction, the spray result improved in trial application.
Formulation lesson: In water-based resin systems, a crosslinker should not be selected only by NCO content. Compatibility and dispersion quality can decide whether the film is clear and uniform or whether particles, haze, or instability appear.
Related Dongsen crosslinker directions for waterborne and baking systems
Beyond the waterbased polyisocyanates discussed above, formulators working across waterborne, baking, and moisture-cure systems often screen more than one Dongsen direction. Related raw-material categories worth reviewing:
- Waterbased polyisocyanate (WD series) — first direction for 2K room-temperature waterborne wood and industrial coatings.
- Water-based blocked polyisocyanate (BI series) — for 1K baking systems where storage stability and deblocking temperature control matter.
- Moisture-curing polyisocyanate — including water-dispersive crosslinking directions such as WDC-80H.
- How to choose a blocked isocyanate by deblocking temperature and 2K vs 1K crosslinker selection for industrial coatings for deeper selection guidance.
About Dongsen Curing Agents
Shaoguan Dongsen Synthetic Materials Co., Ltd. is a coatings new-materials enterprise focused on curing-agent R&D, smart manufacturing, and application service. Dongsen’s curing-agent design capacity is 26,000 tonnes/year, with over 25 years of curing-agent R&D and production experience.
Dongsen Curing Agents cover adducts, trimers, non-yellowing and yellowing-resistant curing agents, waterborne isocyanates, moisture-curing systems, blocked systems, solvent-free systems, and custom functional directions. For water-based resin formulators, the most relevant directions are waterbased polyisocyanates and water-based blocked polyisocyanates.
Manufactured in Shaoguan, China, Dongsen supplies curing agents and crosslinkers as raw materials to coating and adhesive manufacturers worldwide. Relevant chemical inventory registrations held include China REACH, US TSCA, and IECSC, which supports compliant export-oriented supply for overseas formulators.
Dongsen application support for waterborne coating crosslinker testing
Key Takeaways
- Water-based resins may be water-soluble, water-dispersible, or emulsion-based; each type has different film-formation and resistance limits.
- Good film formation depends on water evaporation, particle packing, coalescence, and polymer-chain interdiffusion.
- Crosslinkers are often needed when water resistance, chemical resistance, adhesion, or heat resistance is not enough.
- WD-8780/8980 is a practical waterbased polyisocyanate screening direction for 2K waterborne systems; BI-series grades fit 1K baking systems.
- Before requesting a grade, provide resin type, pH, hydroxyl value, co-solvent, process condition, and target film problem.
Need a grade recommendation for your water-based coating? Send your resin information and target performance requirements. Dongsen can help screen a suitable waterbased polyisocyanate or blocked isocyanate direction.
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FAQ
Are water-based resins completely VOC-free?
No. Water-based resins reduce solvent reliance, but many systems may still contain co-solvents, neutralizing agents, or film-forming aids. Always check the final formulation and local VOC requirement.
What is the main difference between water-dispersible and emulsion resins?
Water-dispersible resins usually have finer particles and can appear transparent or translucent, while emulsion resins often have larger latex particles and appear milky. Their film performance depends on particle coalescence and formulation design.
Why does a water-based coating need a crosslinker?
A crosslinker helps improve final film resistance, including water resistance, solvent resistance, chemical resistance, adhesion, hardness, and heat resistance.
Which Dongsen product direction fits 2K waterborne coatings?
Dongsen WD-series waterbased polyisocyanates are the first direction to screen for many 2K waterborne coating systems. Compatibility, pH, pot life, and NCO/OH ratio should be tested with the actual resin.
Which direction fits 1K water-based baking coatings?
Dongsen water-based blocked polyisocyanates, such as BI-series grades, fit 1K baking systems where storage stability and deblocking temperature are important.
What information should I provide before requesting a sample?
Provide resin type, hydroxyl value, solid content, pH, co-solvent, application field, curing condition, and the film problem you want to solve.
About the author — Vicky Zhao
Overseas Technical Support, Dongsen. Vicky works with international coating and adhesive formulators on waterbased and blocked polyisocyanate crosslinker selection, sample screening, and application troubleshooting. Connect on LinkedIn.
Send Your Water-Based Resin Formulation Requirement
Share your resin type and target film problem, and Dongsen will help screen a suitable crosslinker direction.
- ✅ Waterbased polyisocyanate grade screening
- ✅ 1K baking blocked-isocyanate direction selection
- ✅ TDS, sample, and formulation discussion support
- ✅ Compatibility and application-condition questions before scale-up