2750 vs 2760 vs 2780 vs 2505 cannot be decided from a public performance ranking. All four grades share one Longchang page, one chemistry description, one dose range and one system boundary. The only grade-by-grade values published are overlapping viscosity ranges. Treat viscosity as a handling specification, then request the missing functional and cure evidence.
1,000–4,000 mPa·s
1,000–8,000 mPa·s
5,000–30,000 mPa·s
4,000–12,000 mPa·s
Start from the shared public evidence
The shared product page describes all four as 100% active, multi-component modified polydimethylsiloxane. It recommends 0.1–3.0% of total formulation, permits any-stage or later addition and marks UV and solvent systems suitable while excluding water-based systems. It does not publish separate application, dose or performance claims for each grade.
Preserve the exact viscosity ranges
| Grade | Published viscosity at 25°C | Overlap | What it can support |
|---|---|---|---|
| 2750 | 1,000–4,000 mPa·s | Overlaps 2760 | Receiving and handling specification only |
| 2760 | 1,000–8,000 mPa·s | Overlaps every other band partly | Does not prove a mid-performance grade |
| 2780 | 5,000–30,000 mPa·s | Overlaps 2760 and 2505 | Higher upper viscosity, not higher efficacy |
| 2505 | 4,000–12,000 mPa·s | Overlaps 2760 and 2780 | Cannot be ranked from viscosity alone |
Do not turn viscosity into performance
Viscosity can affect pumping, weighing, dispersion speed and addition accuracy. It does not independently establish wetting, leveling, slip, release, anti-graffiti, cure incorporation or abrasion resistance. The overlapping ranges also mean a batch of one grade can approach another grade’s published band. Require product-specific performance data before assigning a “stronger” or “faster” label.
Require proof before calling the family reactive
The site’s large application table places the family in a reactive-additive category, but the product section does not identify an acrylate, hydroxyl, epoxy or other functional group; it provides no equivalent weight, functionality, conversion or extractables data. Ask the supplier which group reacts with which binder, at what stoichiometry and under what cure conditions. Until then, “reactive” is a category label rather than verified cure chemistry.
Exclude waterborne systems
The shared page explicitly marks water-based systems outside the target window. Do not use the 0.1–3.0% range to justify a waterborne trial. For UV or solvent work, record the exact resin, monomer or solvent package and cure mechanism. Compatibility in one solvent or oligomer does not establish compatibility in another.
Normalize addition and temperature
Because the grades span wide viscosity ranges, condition containers at a defined temperature before weighing. Record addition stage, predilution if supplied by the manufacturer, mixing shear and aging. Any-stage addition is permitted publicly, but that does not mean every stage produces the same dispersion, cure or surface migration.
Verify the grade on the container, delivery note and COA before opening a trial. Because one public page covers four products, a generic family TDS is not enough to establish which viscosity acceptance band or functional claim applies to a shipped lot. Retain a reference sample and record its batch number.
Use a controlled family matrix
| Trial set | Change | Primary observation | Release gate |
|---|---|---|---|
| A | Unchanged UV/solvent control | Viscosity, appearance, cure and adhesion baseline | Rub, recoat and storage |
| B–E | One grade each at common low dose | Handling, compatibility and target surface KPI | Cure, adhesion and defects |
| F–H | Optimize only viable grade | Dose response within 0.1–3.0% | Extractables, rub, block and recoat |
| I | Supplier-confirmed reactive control | Conversion or extractables method | Durability and aging |
Prepare uniform UV films
ASTM D823 describes practices for preparing coating films of uniform thickness on test panels. Fix wet and dry film build, substrate, lamp type, irradiance, dose and line speed. Unequal film thickness or UV exposure can look like a grade effect.
Measure gloss without treating it as cure
ASTM D523 covers specular gloss measurement. Record geometry and film condition. A gloss change can indicate flow or surface segregation, but it does not prove conversion, adhesion or abrasion resistance. Pair gloss with a cure method appropriate to the resin and photoinitiator system.
Check adhesion and recoat
ASTM D3359 provides tape-test methods for coating adhesion. Compare the same cure age and film build, document the substrate and locate failure. Apply the intended next coat, ink or adhesive at target and extended intervals. Surface enrichment can improve one appearance metric while weakening the next interface.
Decision rules
- Use the four viscosity bands for receiving and handling, not performance ranking.
- Do not describe a grade as more reactive without product-specific functionality and cure data.
- Do not screen the family in waterborne systems against the public exclusion.
- Approve a grade only after one controlled UV or solvent matrix passes cure, adhesion, appearance and recoat gates.
Information to send with an inquiry
Provide the exact grade under consideration, vehicle chemistry, UV or solvent status, current formulation viscosity, addition stage, mixing temperature, target surface failure, film build, UV lamp and dose or drying schedule, adhesion/recoat requirements and desired regulatory documents.
Ask Longchang for product-specific 2750, 2760, 2780 and 2505 data.