Polyisocyanate Crosslinkers for Shoe Sole Adhesives: SA-1003, SA-1007 & SA-1009
Updated: 2026
Quick Answer: Dongsen SA-1003, SA-1007 and SA-1009 are polyisocyanate crosslinkers used in 2K PU shoe sole adhesives, with 20–40% solid content, 4.2–7.5% NCO, low free monomer ≤0.1% and ethyl acetate as solvent. They are designed for footwear bonding lines that need strong adhesion between shoe-sole layers, pale colour and lower discoloration risk.
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What is a polyisocyanate crosslinker for shoe sole adhesives?
A polyisocyanate crosslinker is an isocyanate-based raw material added to 2K polyurethane adhesive before shoe sole bonding. It helps improve bonding strength, heat resistance, aging resistance and layer-to-layer adhesion between rubber, EVA, PU, TPU, leather and related footwear materials.
Dongsen supplies polyisocyanate raw materials for adhesive formulation. Dongsen does not supply finished shoe adhesive, finished footwear glue, finished shoe soles or finished footwear products. The SA series is intended for adhesive manufacturers and footwear material suppliers who need a crosslinker for 2K PU adhesive systems.
Why does shoe sole bonding need a crosslinker?
Shoe sole bonding is not only a simple surface attachment. The adhesive layer must survive flexing, heat activation, pressing, storage, transport and humid climates. A PU adhesive without enough crosslinking may show weaker peel strength, softening under heat, edge opening or reduced durability after hot and humid storage.
Polyisocyanate crosslinkers help build a denser adhesive network. In practical shoe production, this can support stronger bonding between outsole, midsole, upper material and sole layers, especially when the adhesive must bond mixed substrates such as rubber, EVA, PU, TPU and leather.
| Footwear bonding issue | Why it matters | How SA series crosslinkers help |
|---|---|---|
| Peel strength | Sole layers must resist pulling, bending and repeated flexing. | Provides additional crosslink density in 2K PU adhesive systems. |
| Heat activation | Many footwear lines reactivate adhesive before pressing. | Supports a stronger bond line after heating and pressing. |
| Humidity aging | Shoes may be stored or shipped in tropical climates. | Improves bond stability compared with weakly crosslinked adhesive layers. |
| Light-coloured soles | White, pastel and transparent materials are sensitive to discoloration. | SA grades are pale-coloured and designed for lower discoloration risk. |
Takeaway: For footwear adhesive manufacturers, the main selection question is not only "which crosslinker has higher NCO," but "which grade gives the right balance of bonding strength, colour stability, dosage and working time."
Why does shoe sole adhesive lose peel strength after heat aging?
Peel strength loss after heat aging is often linked to an adhesive network that is not strong enough for the real production and storage conditions. In 2K PU shoe sole adhesives, a suitable polyisocyanate crosslinker helps improve the crosslink density of the bond line, so the adhesive layer can better resist heat activation, pressing, flexing and hot-humid storage.
For dark or general-purpose rubber, EVA, PU and TPU sole bonding, SA-1003 is usually a balanced first trial grade. If the bonding target requires a stronger crosslinking response, SA-1007 should be tested because it has a higher NCO direction than SA-1003.
Why can light-coloured shoe soles show visible bond-line discoloration?
White, pastel and transparent shoe materials are more sensitive to visible bond-line colour. Instead of selecting only by maximum NCO content, adhesive manufacturers should compare peel strength, colour stability, pot life and aging results together. SA-1009 should be included in the test plan when a lower-solids and lower-NCO direction is preferred for colour-sensitive bonding trials.
What should be tested before replacing a shoe adhesive crosslinker?
Before replacing an existing crosslinker, test the actual PU adhesive formula, outsole material, activation temperature, press time, pot life, open time, peel strength after aging and failure mode. Do not judge the grade only by initial tack or by NCO percentage; footwear bonding performance depends on both the crosslinker and the factory process window.
Which Dongsen SA grade should I choose?
Dongsen SA series includes three main grades — SA-1003, SA-1007 and SA-1009. All three use ethyl acetate as solvent and have low free monomer ≤0.1%; the difference is mainly solid and NCO content, which affects dosage, bonding-strength direction and suitability for light-coloured shoe materials.
| Model | Solid % | NCO % | Free Monomer | Viscosity | Solvent | Best-fit direction |
|---|---|---|---|---|---|---|
| SA-1003 | 40±1 | 7.2±0.3 | ≤0.1 | Approx. 11 s (flow cup) | Ethyl Acetate | Balanced general bonding |
| SA-1007 | 40±1 | 7.5±0.3 | ≤0.1 | Approx. 11 s (flow cup) | Ethyl Acetate | Higher NCO / stronger crosslink |
| SA-1009 | 20±1 | 4.2±0.3 | ≤0.1 | Approx. 11 s (flow cup) | Ethyl Acetate | Lower NCO / light-colour sensitive |
All values are typical reference values and are subject to the current TDS/COA for each grade.
Product summary: SA-1003 and SA-1007 both run 40±1% solids; SA-1007's 7.5±0.3% NCO is the stronger-crosslinking direction, while SA-1003's 7.2±0.3% NCO is the balanced general-purpose option. SA-1009 sits lower at 20±1% solids and 4.2±0.3% NCO, the direction to trial on white, pastel or transparent soles where bond-line colour matters. All three keep free monomer ≤0.1% in ethyl acetate, so final grade choice should be confirmed by peel strength after aging, colour stability and pot life in the actual adhesive formula.
How to select SA-1003, SA-1007 or SA-1009 by application?
Screen on two questions first: how strong a bond the line needs, and how colour-sensitive the substrate is. A practical workflow is to start trials with SA-1003 as a balanced reference on general rubber, EVA, PU and TPU soles, then branch from there — move toward SA-1007 when peel strength or crosslink density needs to go higher (its 7.5±0.3% NCO is the stronger direction), or toward SA-1009 when the sole material is white, pastel or discoloration-sensitive (its lower 20±1% solids and 4.2±0.3% NCO is the colour-friendly direction).
A factory running both dark and light systems can keep SA-1003 for general bonding and add SA-1009 for colour-critical lines, which covers a wider testing range with two grades. In every case, decide on peel strength after aging, colour stability, pot life and the factory's own process window rather than on NCO% alone.
What processing information should be tested before production?
Polyisocyanate crosslinker performance depends on the adhesive formula and factory process. Before mass production, the adhesive manufacturer should confirm mixing ratio, pot life, open time, heat activation window, press conditions and final bonding strength after aging.
| Test item | Why it matters | What to check |
|---|---|---|
| Mixing ratio | Too little crosslinker may reduce peel strength; too much may shorten working time. | Test several dosage levels based on adhesive solids and target bond strength. |
| Pot life | Mixed 2K adhesive changes over time after crosslinker addition. | Check viscosity rise, brushing/spraying performance and final peel strength over time. |
| Heat activation | Footwear bonding lines often need heat before pressing. | Confirm activation temperature and time with the actual sole tunnel. |
| Pressing condition | Bond-line contact pressure affects final adhesion. | Test pressure, pressing time and substrate fit. |
| Aging resistance | Finished shoes may face heat, humidity and storage stress. | Run peel strength after hot/humid aging and compare failure mode. |
Production reminder: Do not judge the crosslinker only by initial tack. For footwear adhesive systems, peel strength after aging and failure mode are more important than the first few minutes of bonding feel.
Can SA series be used in waterborne PU shoe adhesives?
SA-1003, SA-1007 and SA-1009 are designed for solvent-based 2K PU adhesive systems using ethyl acetate as solvent. If your formulation is a waterborne PU adhesive, a water-dispersible polyisocyanate direction should be evaluated instead of directly replacing the SA series.
For waterborne crosslinking needs, you can review Dongsen waterbased isocyanate options or contact us with your PUD type, pH, solid content, target pot life, substrate and final testing standard.
Related Dongsen pages:
- Isocyanate Hardener product category
- Adhesives for Footwear & Shoes industry page
- Waterborne polyisocyanate hardener for 2K PU coatings
- Waterborne polyurethane dispersion (PUD) crosslinker selection guide
- 3 types of polyurethane curing agents
What makes Dongsen suitable for footwear adhesive crosslinker supply?
Shaoguan Dongsen Synthetic Materials Co., Ltd. is a China-based curing-agent manufacturer focused on isocyanate hardeners, polyisocyanate crosslinkers, blocked isocyanates, moisture-curing polyisocyanates, waterborne isocyanates and custom functional curing-agent systems.
Dongsen has 25+ years of curing-agent R&D and production experience, with a curing-agent design capacity of 26,000 tonnes/year. The company supports product supply, application testing, formulation discussion, TDS/MSDS/COA documentation and sample evaluation for qualified adhesive manufacturers. For international buyers, product selection can be based on the buyer's adhesive type, substrate, process window and target market, with compliance information discussed under China REACH, TSCA, IECSC and the latest product documentation.
Key takeaways for footwear adhesive manufacturers
- SA-1003 is a balanced starting grade for 2K PU shoe sole adhesive crosslinking.
- SA-1007 has a higher NCO level and is suitable when stronger crosslinking response is required.
- SA-1009 should be included in trial plans for white, pastel or colour-sensitive shoe materials, but final selection must still be confirmed by peel strength, aging resistance, pot life and colour stability.
- All three SA grades use ethyl acetate as solvent and have low free monomer ≤0.1%.
- Final grade selection should be confirmed by peel strength, aging test, colour stability, pot life and factory processing trials.
Request a shoe sole adhesive crosslinker sample
Tell us your PU adhesive type, outsole material, midsole or upper material, colour requirement, activation temperature, press condition, target peel strength, pot life requirement, current dosage range and estimated monthly usage. Our team will review whether SA-1003, SA-1007 or SA-1009 should be tested first.
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- ✅ TDS / MSDS / COA available on request
- ✅ Sample support for qualified footwear adhesive manufacturers
- ✅ Grade selection by substrate, colour sensitivity and bonding target
- ✅ SA-1003, SA-1007 and SA-1009 comparison based on real test conditions
- ✅ WhatsApp backup for urgent technical or purchasing questions
FAQ
What is polyisocyanate crosslinker used for in shoe sole adhesives?
Polyisocyanate crosslinker is used to improve bonding strength, heat resistance and aging resistance in 2K PU shoe sole adhesives. It helps the adhesive form a stronger crosslinked network after mixing and pressing.
Which SA grade should I test first?
SA-1003 is the balanced starting grade for many solvent-based 2K PU shoe adhesive systems. If higher crosslinking response is needed, test SA-1007; if light-colour sensitivity is the main concern, include SA-1009 in the comparison plan and confirm it by peel strength, aging resistance, pot life and colour stability.
What is the difference between SA-1003 and SA-1007?
SA-1003 has 40±1% solid content and 7.2±0.3% NCO, while SA-1007 has 40±1% solid content and 7.5±0.3% NCO. SA-1007 is the stronger NCO direction for higher crosslinking demand.
Which SA grade should I include for white or pastel shoe sole trials?
SA-1009 should be included in the trial plan for white, pastel or colour-sensitive shoe sole adhesive systems because it has lower solid content and lower NCO content than SA-1003 and SA-1007. However, it should not be selected by colour requirement alone; peel strength, aging resistance, pot life and the actual PU adhesive formula must also be tested.
Are SA-1003, SA-1007 and SA-1009 solvent-based?
Yes. SA-1003, SA-1007 and SA-1009 use ethyl acetate as solvent and are positioned for solvent-based 2K PU adhesive systems.
Can SA series replace waterborne PU adhesive crosslinkers?
No direct replacement should be made without testing. SA series is designed for solvent-based PU adhesive systems. For waterborne PU adhesive systems, a water-dispersible polyisocyanate direction should be evaluated separately.
What information should I provide when asking for a suitable grade?
Please provide your PU adhesive type, substrate, shoe-sole material, colour requirement, target peel strength, process condition, dosage range, monthly usage and destination country. This helps Dongsen recommend a more suitable starting grade.