3 Types of Waterbased Resins and Film Formation Mechanism
Updated: 2026
Quick Answer: Water-based resins are polymer binders dissolved or dispersed in water for coatings, inks, adhesives and surface-treatment systems. Dissolved-polymer and particle-based binders form films differently: particle packing and coalescence apply to dispersions and latex systems. Crosslinkers are one formulation variable to evaluate when the dried film does not meet resistance requirements; resin functionality, compatibility and curing conditions determine the result.
What are water-based resins?
Water-based resins are polymer materials that use water as the main medium. Polymer chains can be dissolved in water or polymer particles can be dispersed in it. Latex binders, often called emulsions in coating practice, are also particle dispersions; particle size and appearance alone do not define a separate performance class. The resin acts as the film-forming binder, while additives, pigments, fillers, coalescents and crosslinkers adjust application and final film properties.
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 guide explains the main resin types, the film-formation process, and how to connect a reactive resin system with Dongsen crosslinker screening. It keeps physical drying, particle coalescence and chemical crosslinking distinct.
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 | Polymer particles are dispersed in water; appearance depends on particle size, concentration and formulation. | 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 | Latex polymer particles are dispersed in water and often appear milky; they are not necessarily larger than every other dispersion. | Film development requires adequate particle deformation and chain interdiffusion; final resistance depends on polymer chemistry and the complete formulation. | Emulsifier residue, water sensitivity, particle coalescence at low temperature. |
Takeaway: A dissolved-polymer solution concentrates as water leaves, whereas particle-based dispersions and latex binders also need adequate deformation and coalescence. Neither route guarantees resistance without checking resin chemistry and curing conditions.
How do water-based resins form a continuous film?
In a particle-based waterborne coating, dispersed polymer particles must move from a wet, separated state to a continuous film. The stages below describe dispersion and latex film formation. A truly water-soluble polymer system instead concentrates dissolved chains as water evaporates; it should not be described as following the same particle-packing sequence.
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?
Polymer chains can interdiffuse across particle boundaries as the film develops. In a chemically crosslinkable system, compatible reactive groups can also form a network. These processes may overlap; crosslinking does not always wait until physical film formation is complete. A crosslinker may change water, solvent or chemical resistance, adhesion, hardness or flexibility, but the outcome depends on the resin, reaction balance and curing conditions.
Why do water-based coatings still need crosslinkers?
Water-based resin selection solves only part of the formulation problem. The dried film may also need to resist water, alcohol, cleaning agents, blocking, abrasion or heat. Where the resin has compatible reactive functionality, a crosslinker can help form a network. It remains one key formulation variable alongside the binder, additives, substrate and drying or baking process.
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-8980, WD-8300 | Check resin compatibility, pH, co-solvent, mixing order, pot life, and target NCO/OH ratio. |
| 1K water-based baking coating | Evaluate a blocked crosslinker for heat-activated reaction with a hydroxyl-containing resin | Water-based blocked polyisocyanate | BI-35C, BI-35D, BI-70C, BI-70D | Screen by ionic type and solids, then verify reference deblocking data against resin functionality and the complete bake schedule. |
| 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: Screen a WD crosslinker for a reactive 2K waterborne resin, and a water-based blocked polyisocyanate for a hydroxyl-containing 1K baking system. The process choice does not prove compatibility or film performance; both require formulation testing.
Dongsen grade examples for waterborne coating formulators
All values are typical and subject to the current TDS/COA.
| Dongsen grade | Product direction | Solid % | NCO / valid NCO % | Residual species (see note) | Viscosity (cps, 25°C) | Screening context |
|---|---|---|---|---|---|---|
| WD-8980 | Water-dispersible aliphatic polyisocyanate | 80.0±2.0 | 15.0±1 | Free monomer ≤0.3% | 300±200 | Candidate for reactive 2K waterborne resin screening; confirm compatibility, mixing and pot life. |
| WD-8300 | Water-dispersible aliphatic polyisocyanate | 100 | 21.8±0.5 | Free monomer ≤0.3% | 2500±1000 | Candidate for reactive 2K waterborne resin screening; confirm compatibility, mixing and pot life. |
| BI-35C | Anionic water-soluble blocked polyisocyanate | 35 | 3.5±0.5 | Free NCO ≤0.2% | 1000±500 | Candidate for a hydroxyl-containing 1K baking system; reference deblocking 120°C. Confirm the complete bake schedule. |
| BI-35D | Anionic water-soluble blocked polyisocyanate | 35 | 3.6±0.5 | Free NCO ≤0.2% | 2500±500 | Candidate for a hydroxyl-containing 1K baking system; reference deblocking 130–140°C. Confirm the complete bake schedule. |
| BI-70C | Anionic water-dispersible blocked polyisocyanate | 70 | 7.7±0.5 | Free NCO ≤0.2% | 2500±1000 | Candidate for a hydroxyl-containing 1K baking system; reference deblocking 120°C. Confirm the complete bake schedule. |
| BI-70D | Anionic water-dispersible blocked polyisocyanate | 70 | 7.2±0.5 | Free NCO ≤0.2% | 4000±1500 | Candidate for a hydroxyl-containing 1K baking system; reference deblocking 130–140°C. Confirm the complete bake schedule. |
Reading the data: WD rows report reactive NCO and free-monomer limits. BI rows report valid NCO and residual free NCO, not a free-monomer test. Free monomer, free NCO and valid NCO are different measurements and must not be treated as interchangeable.
Parameter summary: WD-8980 is listed at 80.0±2.0% solids, 15.0±1% NCO and 300±200 cps at 25°C. BI-35C is listed at 35% solids, 3.5±0.5% valid NCO and 1000±500 cps at 25°C. These are grade specifications for comparison, not proof of easier dispersion, storage stability or final coating performance. All values are typical and subject to the current TDS/COA.
Deblocking is not a complete cure window: The BI reference temperatures describe deblocking data. They do not establish a successful bake temperature or time for every formulation. Confirm the current grade TDS, resin functionality, catalyst package, film thickness, substrate temperature and bake duration using the actual system.
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 becomes available for reaction during heating; storage stability and the complete bake profile require validation. |
| 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. | Hydroxyl-containing 1K baking systems; grade-specific application and process confirmation remain necessary. |
| 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: Start with whether the process permits mixing before use or requires a heat-activated 1K formulation. Then verify resin functionality, compatibility and the full curing schedule. A reference deblocking temperature alone cannot decide the bake window.
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
Particles, haze or an unexpected viscosity change after crosslinker addition are reasons to review compatibility and mixing. Check resin ionic character, pH, co-solvent balance, dilution method and mixing order. Compare the mixed formulation with the resin-only baseline under the same conditions before attributing the problem to one ingredient.
Formulation lesson: NCO content alone cannot establish compatibility. Record how the mixture changes during the required working time, and test the cured film under the intended process conditions. Share these observations with your resin and process details when requesting screening support.
Related Dongsen crosslinker directions for waterborne and baking systems
Related raw-material categories help distinguish process routes; category membership alone does not establish resin compatibility or grade suitability.
- Waterbased Polyisocyanates — review this direction for reactive 2K waterborne systems.
- Water-Based Blocked Polyisocyanates — review this direction for hydroxyl-containing 1K baking systems.
- Moisture-Curing Polyisocyanate Prepolymers — a separate process route; do not assume aqueous mixing compatibility from the category name.
For further selection work, compare reference deblocking data with the actual bake schedule, and compare the processing requirements of 2K mixing with those of 1K heat activation.
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. Request current grade-specific documentation for the intended market; chemical inventory status alone does not establish compliance with every requirement of a final formulation or use.
Key Takeaways
- Water-based resins may be water-soluble, water-dispersible, or emulsion-based; each type has different film-formation and resistance limits.
- Particle-based film formation involves water evaporation, particle packing, coalescence and chain interdiffusion; dissolved-polymer solutions follow a different physical route.
- Crosslinkers are one variable to evaluate when resistance is insufficient; compatible reactive groups and adequate curing are essential.
- WD-8980 is a screening candidate for reactive 2K waterborne systems; water-based blocked polyisocyanates are a screening direction for hydroxyl-containing 1K baking systems.
- Before requesting a grade, provide resin type, pH, hydroxyl value, co-solvent, process condition, and target film problem.
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?
Latex binders are also polymer dispersions. Particle size, appearance and stabilization vary, so transparent versus milky appearance alone cannot establish film quality or resistance. For particle-based binders, check coalescence conditions and the full formulation.
Why does a water-based coating need a crosslinker?
A crosslinker can form a chemical network when compatible reactive groups are present. Whether that improves a required property must be tested with the actual resin and curing conditions.
Which Dongsen product direction fits 2K waterborne coatings?
Dongsen WD-series waterbased polyisocyanates are a direction to screen for reactive 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 are a direction to screen with hydroxyl-containing resins for 1K baking systems. Validate storage stability and the complete curing schedule; reference deblocking data alone cannot confirm either.
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.
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