Dongsen Chemicals

Dongsen Chemicals Leading Manufacturer of Polyisocyanate PU Hardener Doxu is a leading manufacturer and supplier of chemical coating materials and products since 1988.

We aim to provide a full range of polyisocyanate curing agents/ crosslinkers/ PU hardener, including TDI based aromatic, HDI based aliphatic, moisture curing , waterborne and blocked isocyanates. Doxu polyisocyanate curing agents can serve various industries: automotive, wood furniture, construction, packaging, electronics & appliances, can & coil coatings, industrial coatings, floor coatings. He

adquartered in Guangzhou, Doxu has three manufacturing bases located in Guangdong, China, spanning a total area of 150,000 square meters. We always strive to deepen our efforts in independent manufacturing, R&D, quality control to provide top-tier coating solutions to our customers. Over our journey, Doxu has witnessed a huge leap forward and established a global presence in the coating industries. Our high-performance polyisocyanate curing agents has won global recognition and trust. At Doxu, our vision is to go beyond the industry standard to provide high-performance chemical products to our customers. We are committed to technical innovation, customer satisfaction and sustainable development.

Two Vietnamese footwear factories asked us the same question last month — "which waterborne crosslinker for our pale lea...
18/07/2026

Two Vietnamese footwear factories asked us the same question last month — "which waterborne crosslinker for our pale leather topcoat?" They needed two different answers, and the deciding factor wasn't performance. It was whether the line has an oven.

If there's no oven, the honest choice is a 2K water-dispersible aliphatic polyisocyanate — WD-8980, ~80% solids, 15% NCO, ambient cure. It disperses under ordinary stirring at around 300 cps, so no high-shear rig. The trade-off you accept is pot life.

If there's an oven or a lamination station, the choice is a blocked isocyanate — BI-70D deblocks at 130–140°C and stays chemically capped until the bake releases it. We ran it at 10% in an acrylic system for textile lamination: clean release at 140°C, storage stable. For a water-soluble 1K route, BI-35D covers the low-solids case.

One caveat from the floor: a heavily pigmented black synthetic-leather finish seeded after crosslinker addition. A more hydrophilic anionic grade cleared it. Dark, high-pigment, high-shear systems deserve their own dispersion screen — spec sheets don't catch that.

And the yellowing point buyers keep getting wrong: resistance to yellowing comes from the aliphatic HDI backbone, not from the fact that it's waterborne. The carrier doesn't protect the shade — the chemistry does.

The crosslinker is the variable that sets crosslink density, chemical resistance and yellowing — not the base resin. Which way does your line run — pot life, or deblocking temperature? Selection guide and TDS in the first comment.

10/07/2026

Safety in production is an ongoing commitment, not a task with an endpoint.

Dongsen Synthetic Chemicals promotes learning through competition and strengthens emergency preparedness through practical drills, ensuring that everyone understands workplace safety and is equipped to respond effectively in an emergency. These efforts provide solid protection for safe and reliable production.

Without matching hardener viscosity to your spray gun's atomization window, without controlling free monomer for a clean...
01/07/2026

Without matching hardener viscosity to your spray gun's atomization window, without controlling free monomer for a clean matte or gloss finish, without knowing where the yellowing tolerance line actually sits — spray coating problems rarely start at the gun. They start at hardener selection.

For indoor wood and furniture spray lines, drying speed, film hardness, and gloss consistency all trace back to which polyisocyanate hardener sits in your 2K system, not the spray settings alone.

Three starting directions worth comparing: HDX-50BA (TDI trimer, ~1000 cps, fast through-dry) for booths where cure speed and a reliable matte finish matter most; HDX-960E (TDI trimer, ~110 cps) where lower viscosity and compatibility with acrylic-containing systems matter more than dry time; and HDX-175MPX (HDI biuret, ~210 cps) once yellowing resistance becomes a spec requirement rather than a nice-to-have. The first two are aromatic chemistry, best framed for indoor use only — the third moves into aliphatic chemistry for lightfastness. All values are typical and subject to the current TDS/COA.

Before locking a grade, worth checking:

-Target viscosity window for your gun and system solids.

-Gloss/matte target confirmed before hardener chemistry is fixed.

-Whether yellowing resistance is a hard spec (aliphatic) or acceptable for indoor-only use (aromatic)

-Free monomer and pot life validated against your actual line speed

Whatever the application method — spray, roll, brush, or dip — the hardener is what ultimately decides drying speed, hardness, and yellowing resistance downstream, not the equipment.

See the link in the first comment for the full spray/roll/brush/dip hardener selection guide. What's the constraint you've hit most switching between spray and roll lines — viscosity, drying speed, or yellowing?

Your waterborne 2K topcoat mixes clean in the lab. Then you add the water-dispersible polyisocyanate — and the cured bla...
29/06/2026

Your waterborne 2K topcoat mixes clean in the lab. Then you add the water-dispersible polyisocyanate — and the cured black film comes back speckled with particles.

In waterborne 2K PU, that's rarely just a resin defect. The hardener has to survive the real package: resin type, pH, neutralizer, pigment dispersion, co-solvent and mixing method. A grade that looks right on a spec sheet can still seed particles if its hydrophilicity and viscosity don't match that system.

In one Southeast-Asian project — a black waterborne topcoat for high-end synthetic leather, built for a Vietnam end-line — a high-solids water-dispersible grade (80% solids, 15% NCO) threw particles after addition. Stepping to a lower-viscosity grade (70% solids, 13% NCO, ~150 cps) cleared the dispersion, and the re-sprayed panels passed.

A practical 3-grade screening axis:
- WD-8980 — 80% solids / 15% NCO — highest active content for crosslink density.

- WD-8970 — 70% solids / 13% NCO / ~150 cps — lower viscosity when a high-solids grade seeds particles.

- A conventional waterborne polyisocyanate — benchmark reference for evaluation.

All three are HDI-based — aliphatic. The non-yellowing performance comes from the chemistry, not from being "waterborne"; a waterborne aromatic system would still yellow. Whichever carrier you run, the water-dispersible hardener is the variable that decides dispersion stability, crosslink density and color retention.

If you're screening a waterborne 2K topcoat and want a starting grade plus TDS, see the link in the first comment.

When a high-solids water-dispersible hardener seeds particles in your package, do you step viscosity down first, or re-check neutralization and co-solvent first?

We were delighted to welcome a valued international partner for a multi-day visit to our Guangzhou office and Shaoguan m...
24/06/2026

We were delighted to welcome a valued international partner for a multi-day visit to our Guangzhou office and Shaoguan manufacturing base. 🤝

Our guest met with our technical and commercial teams and toured the Shaoguan plant, seeing our polyisocyanate hardener and crosslinker production firsthand — from quality control to how each grade is matched to real coating and adhesive applications.

Visits like this are where lasting partnerships are built: time spent together, direct visibility into how products are made and tested, and alignment on the technical requirements that matter.

Thank you for making the journey — we look forward to a long and productive partnership ahead.

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18/06/2026

Fast dispersion · High clarity & gloss · Excellent compatibility
WD-89 Series Waterborne Curing Agent — built for waterborne coating systems.
Available in three solid-content grades: 80 / 75 / 70, flexible for different formulation needs.
Higher quality, better value — an upgrade for your waterborne finishes.

On a coil line the peak metal temperature is fixed — your crosslinker has to meet it, not the other way around.Run a blo...
15/06/2026

On a coil line the peak metal temperature is fixed — your crosslinker has to meet it, not the other way around.

Run a blocked isocyanate with a 150°C deblocking window on a line that peaks near 130°C, and the panel can look cured, pass cross-hatch, then fail MEK double-rubs weeks later. Undercure hides well.

This is the crosslinker decision in 1K baking topcoats for pre-coated metal — coil, appliance, steel furniture. Many of these lines run a melamine / amino-resin crosslinker: it works, but cure leans on acid catalysis and bake schedule, and aromatic chemistries can yellow on white and pastel topcoats. A blocked aliphatic (HDI) isocyanate gives a tunable deblocking window plus the lightfastness of an HDI backbone.

Match the deblock to your PMT:

🔹 DXB-3370G — HDI trimer, ~70% solid, deblocking 80–100°C. Lower-bake or heat-sensitive lines.
🔹 DXB-3375D — HDI trimer, ~75% solid, valid NCO ~11.2%, deblocking 130–140°C. Mainstream coil PMT.
🔹 DXB-3375E — HDI trimer, ~75% solid, deblocking 150°C. Higher line speed / harder cure.

(Free NCO ≤0.2% per reference data; exact values to be confirmed with current TDS.)
Position here is alongside amino-resin crosslinkers — may serve as an alternative for evaluation where aliphatic weatherability and a matched cure window matter, not a blanket replacement.

See the link in the first comment to request the TDS or a sample. Which deblocking window does your coil line actually run at peak — and is your crosslinker matched to it?

A silicone-modified baking coating can pass every resin spec on paper and still fail on the line.The reason is rarely th...
08/06/2026

A silicone-modified baking coating can pass every resin spec on paper and still fail on the line.

The reason is rarely the silicone resin itself. It's the crosslinker chosen by the word "silicone" instead of by the actual oven window.

In metal, coil, and appliance baking systems, a blocked isocyanate only performs if its deblocking temperature matches your bake schedule. Run a crosslinker that deblocks at 150°C through a 120°C oven and you get undercure, weak crosslink density, and film performance that looks fine — until it's tested.

So the real question isn't silicone vs PU. It's: what is your oven temperature?

Three blocked HDI trimer directions to screen by bake window:

🔹 DXB-3370G — 80–100°C deblock, 70±2% solids, 7.5±0.5% valid NCO, PMA carrier. Lower-temperature 1K baking.

🔹 DXB-3375D — 130–140°C deblock, 75±2% solids, 11.2±0.5% valid NCO, Solvent Naphtha 100. Medium-temperature, including coil directions.

🔹 DXB-3375E — 150°C deblock, 75±2% solids, 10.5±0.5% valid NCO. Higher-temperature bakes.

All values are typical reference data and subject to current TDS/COA.

Before you request samples, check: deblocking temp vs your real oven profile, resin hydroxyl compatibility, solvent tolerance, valid NCO ratio, and storage stability vs final film performance.

Want the full crosslinker selection guide? See the link in the first comment — or Request TDS / Sample / Quotation / Ask for a Suitable Grade.

If you run a silicone-modified baking line, what's your actual peak metal temperature — and does your current crosslinker's deblocking window truly match it?

A polyester coil-coated panel can pass T-bend and still fail MEK rub. The usual suspect: a deblocking temperature that d...
01/06/2026

A polyester coil-coated panel can pass T-bend and still fail MEK rub. The usual suspect: a deblocking temperature that doesn't match your PMT.
For polyester-PU coil coatings, match the blocked HDI trimer to your bake schedule:
🔹 DXB-3370G — deblocks 80–100°C (low-bake / heat-sensitive substrates)
🔹 DXB-3375D — 130–140°C (standard PMT)
🔹 DXB-3375E — 150°C (high-PMT industrial)
Benchmarking Covestro's Desmodur BL series? These may serve as alternatives for evaluation.
Request TDS / sample / quotation: https://dongsenchem.com/all-about-polyester-resin-featuresapplications/

Happy Children’s Day! 🌈At Dongsen Chem, we believe that curiosity, creativity, and care are not only important for child...
01/06/2026

Happy Children’s Day! 🌈

At Dongsen Chem, we believe that curiosity, creativity, and care are not only important for children — they also inspire the way we create better chemical solutions.

On this special day, we celebrate every child’s imagination, every colorful dream, and every future full of possibilities.

May every child grow with joy, confidence, and wonder.

Happy Children’s Day from Dongsen Chem.

Explore more: https://dongsenchem.com/

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