Polyester Resin Guide for Coating Formulators
Updated: 2026
Polyester Resin Guide for Coating Formulators
Quick Answer: Polyester resin is a binder family used in coatings, composites, adhesives, and inks. Dongsen does not manufacture polyester resin or finished paint, but when a polyester binder is hydroxyl-functional and designed for polyurethane crosslinking, Dongsen polyisocyanate hardeners are the matching reactive component — HDI biuret (e.g. HDX-175MPX, NCO 16.5±0.5%) for flexibility and adhesion, HDI trimer (HDX-190, NCO 19.8±0.5%) for hardness and faster drying, and blocked polyisocyanates with deblocking temperatures from about 80°C up to 150°C for 1K polyester baking systems.
Need Help Matching a Polyester-OH Binder with a PU Crosslinker?
If your formulation uses a hydroxy-functional polyester binder, the next question is usually which isocyanate hardener or blocked crosslinker direction should be tested. Dongsen supports raw-material selection while keeping the product boundary clear: Dongsen supplies polyisocyanate hardeners and crosslinkers, not polyester resin or finished coatings.
What Is Polyester Resin?
Polyester resin is formed from acid components and alcohol components through condensation chemistry. Coating and composite buyers usually discuss two broad directions: saturated polyester resin and unsaturated polyester resin. The correct choice depends on the formulation, curing route, application method, and required test results.
For polyurethane coating work specifically, the key sub-direction is the hydroxyl-functional polyester: the OH groups on the polyester backbone react with NCO groups on a polyisocyanate hardener to form a crosslinked PU film. That is the point where Dongsen raw materials become relevant.
This article is written for coating and adhesive formulators who need a practical purchasing overview. Dongsen does not supply polyester resin, epoxy resin, nitrocellulose, alkyd or oil-based resin, exterior wall paint, finished industrial paint, or any finished coating product. Dongsen supplies polyurethane raw materials, including isocyanate hardeners, blocked polyisocyanate crosslinkers, waterbased polyisocyanates, moisture curing polyisocyanates, and polyisocyanates for shoe-sole adhesives.
Main Types of Polyester Resin
Saturated Polyester Resin
Saturated polyester resin is a coating binder direction reviewed for metal coatings, baking coatings, automotive-related coatings, can or coil coatings, and selected industrial systems. Final performance depends on the resin, pigment package, solvent or waterborne design, crosslinker, curing schedule, and application process — the resin alone does not determine the result.
When the saturated polyester is hydroxyl-functional and designed for PU crosslinking, the formulator evaluates aliphatic, aromatic, blocked, or waterbased polyisocyanate directions. The OH content of the polyester sets the stoichiometric NCO target, so the NCO% on the hardener TDS (for example 16.5±0.5% on HDX-175MPX, 19.8±0.5% on HDX-190) is a direct selection parameter.
Unsaturated Polyester Resin
Unsaturated polyester resin (UPR) is normally associated with thermoset composite systems — FRP, GRP, molded parts, panels, tanks. The chemistry is C=C double-bond crosslinking, typically initiated with peroxides and styrene as a reactive diluent, not isocyanate crosslinking. This category is useful market background, but it is not Dongsen's supply scope.
If your inquiry is only for UPR or finished composite resin, Dongsen is not the right supplier. If your project also involves polyurethane crosslinkers or hardener systems, Dongsen can review the relevant raw-material direction.
Hydroxyl-Functional Polyester Systems (PU Coatings)
Many buyers say "polyester resin" when they mean a hydroxyl-functional polyester binder for 2K PU or 1K baking PU coating formulation. Here the crosslinker selection is the critical formulation decision. The resin OH value, solvent or waterborne system, curing temperature, pot life target, and end-use testing should be shared before recommending a hardener direction.
Polyester-OH + Dongsen Polyisocyanate: Selection Map
The table below maps common polyester-based formulation directions to a relevant Dongsen polyisocyanate category and a representative grade with real specifications. This is a selection reference, not a substitute for testing.
| Polyester-Based System | Crosslinker Direction | Representative Dongsen Grade | Typical Specs |
|---|---|---|---|
| 2K PU on flexible substrates (polyester-OH + lightfast hardener) | Aliphatic HDI biuret — flexibility, adhesion, lightfast | HDX-175MPX / HDX-175BA | Solid 75±1%, NCO 16.5±0.5%, viscosity 210±90 cps |
| 2K PU needing higher hardness and faster drying | Aliphatic HDI trimer | HDX-190 (or HDX-100 for 100% solids) | HDX-190: 90±1% solids, NCO 19.8±0.5%, 525±75 cps |
| Indoor furniture 2K PU on polyester (yellowing acceptable) | Aromatic TDI adduct | DL-75 | 75±2% solids, NCO 13.0±0.5%, 1500±500 cps |
| 1K polyester baking, low-temp oven line (80–100°C) | Low-temp blocked HDI trimer | DXB-3370G | 70.0±2.0% solids, valid NCO 7.5±0.5%, deblock 80–100°C, PMA carrier |
| 1K polyester baking, standard oven (130–140°C) | Mid-temp blocked HDI trimer | DXB-3375D | 75.0±2.0% solids, valid NCO 11.2±0.5%, deblock 130–140°C, Solvent Naphtha 100 carrier |
| 1K polyester baking, high-temp coil/can line (150°C) | High-temp blocked HDI trimer | DXB-3375E | 75.0±2.0% solids, valid NCO 10.5±0.5%, deblock 150°C, Solvent Naphtha 100 carrier |
| Waterborne 2K PU on polyester-OH dispersion | Water-dispersible HDI polyisocyanate | WD-9100 | 100% solids, NCO 18.0±0.5%, viscosity 2500±1000 cps |
All values above are typical reference data and are subject to the current TDS and COA for each grade. Final selection must be confirmed through formulation testing.
Application Selection Guide
Can, Coil, and Metal Baking Coatings
Polyester binders are widely discussed in can, coil, and metal baking systems. The deciding question is the oven line: a 1K polyester baking coating needs a blocked polyisocyanate whose deblocking temperature is at or just below the line temperature. A 130°C oven pairs poorly with a 150°C-deblock grade, and a 150°C oven over-bakes an 80°C-deblock grade. Match the grade to the line first, then test for chemical resistance, gloss, and flexibility.
Automotive-Related and General Industrial 2K Coatings
For automotive-related coating formulation, separate finished coatings from raw materials. Dongsen does not sell finished automotive paint. Dongsen supplies HDI biuret and HDI trimer raw materials that formulators evaluate with polyester-OH binders for lightfast 2K PU systems. HDI biuret (HDX-175MPX/BA) tends to favor flexibility and adhesion; HDI trimer (HDX-190, HDX-100) tends to favor hardness and faster drying.
Furniture and Indoor 2K Polyester Systems
Indoor furniture finishes with polyester-OH may use an aromatic TDI adduct such as DL-75 (NCO 13.0±0.5%) where yellowing under UV is acceptable. Drying speed and hardness profile fit interior wood and panel finishes, and the resin/hardener ratio is set from the polyester OH value and the hardener NCO%.
Waterborne Polyester-Related Systems
Waterborne 2K PU on a polyester-OH dispersion needs a water-dispersible polyisocyanate. See Dongsen's water-based isocyanate hardener WD-9100 (NCO 18.0±0.5%) as a starting point, then confirm grade fit and dispersing protocol by sending the actual formulation details.
Adhesive Systems Using Polyester Polyols
Polyester polyols appear in selected adhesive discussions. Dongsen's supply scope is the polyisocyanate hardener (not finished adhesive), including hardener directions for shoe-sole adhesive systems (SA-1003 / 1007 / 1009, ethyl acetate carrier, free monomer ≤0.1%). Resin, process, and required testing should be provided before sample selection.
Send the Formulation Details Before Choosing a Grade
If your project is polyester-resin-related, make the inquiry specific: resin or binder type (saturated vs hydroxyl-functional), OH value if known, solvent or waterborne system, application, curing or baking conditions, and what you need from Dongsen. The faster you share the formulation context, the faster the grade recommendation.
Send Your Polyester-Based Formulation Requirement
Share whether your project uses saturated polyester, hydroxyl-functional polyester, a waterbased polyester dispersion, or another binder direction. Dongsen will review whether an isocyanate hardener, blocked polyisocyanate crosslinker, waterbased polyisocyanate, moisture curing polyisocyanate, or shoe-sole adhesive hardener direction is relevant for testing.
- 🔬 TDS request for relevant hardener or crosslinker grades
- 🧪 Sample support for formulation screening
- 📦 Quotation based on quantity and packaging needs
- 🧭 Grade selection support by polyester OH value and baking line
- 🤝 Clear product-boundary review to avoid wrong-product inquiries
FAQ: Polyester Resin and Dongsen Crosslinker Selection
What is polyester resin in coating formulation?
Polyester resin is a binder family used in coating, ink, adhesive, composite, and related formulation work. In PU coatings, the hydroxyl-functional variant is the relevant sub-direction because its OH groups react with NCO on a polyisocyanate hardener to form the crosslinked film.
Does Dongsen manufacture polyester resin?
No. Dongsen does not manufacture or sell polyester resin. Dongsen supplies polyisocyanate hardeners, blocked polyisocyanate crosslinkers, waterbased polyisocyanates, moisture curing polyisocyanates, and related PU raw materials that crosslink with polyester-OH binders.
Which Dongsen grade fits a polyester-OH 2K PU on metal?
For lightfast 2K PU on a polyester-OH binder, HDI biuret HDX-175MPX (NCO 16.5±0.5%) favors flexibility and adhesion, while HDI trimer HDX-190 (NCO 19.8±0.5%) favors hardness and faster drying. Final choice depends on the polyester OH value and target film properties, and should be confirmed by testing against the current TDS.
How is a Dongsen blocked grade matched to a polyester baking line?
Match deblocking temperature to oven temperature: DXB-3370G at 80–100°C for low-temp ovens, DXB-3375C at 120°C, DXB-3375D at 130–140°C for standard lines, and DXB-3375E at 150°C for high-temp coil or can lines.
What is the difference between saturated and unsaturated polyester resin?
Saturated polyester is a coating binder direction (often hydroxyl-functional, paired with isocyanate hardeners in PU systems). Unsaturated polyester is a thermoset composite resin crosslinked through C=C double bonds, typically with peroxide initiators and styrene. Dongsen polyisocyanates pair with hydroxyl-functional polyester, not with unsaturated polyester.
Does Dongsen supply epoxy paint, exterior wall paint, or finished industrial paint?
No. Dongsen does not supply epoxy paint, exterior wall paint, finished industrial paint, finished coating, nitrocellulose lacquer, oil-based or alkyd resin, or any finished resin product.
What should I send Dongsen if I use a polyester resin system?
Send resin or binder type, OH value if known, application, solvent or waterborne design, curing or baking conditions, target test requirements, quantity, and whether you need TDS, sample, quotation, or grade selection support.