Quick answer: buyers choosing additives for 2K polyurethane clearcoats usually get a better shortlist when they stop treating every clear-finish problem as the same job. CHLUMIAG® 3467 should move first when the clearcoat is still fighting compatibility-sensitive anti-cratering, substrate wetting, or broader formulation instability. CHLUMIFE® 3370 belongs earlier when the buyer needs a reactive 2K PU leveling and gloss-hold route for a cleaner clear film. CHLUMIFE® 3307X deserves earlier review when the clearcoat can already form but still needs post-cure scratch resistance, surface smoothness, and recoat-aware durability.
That is the commercially useful split. In clearcoats, defects stay visible. A transparent film does not hide crater edges, weak flow-out, or mar damage the way a more forgiving pigmented finish sometimes can. So the first additive decision should match the failure the buyer actually sees.
Why 2K polyurethane clearcoats need a narrower additive screen
Longchang already has adjacent pages for 2K polyurethane primers, 2K polyurethane topcoats, and the wider CHLUMICRYL® Coating and Ink Additives branch. Those pages help buyers understand the broader system.
This page answers a tighter B2B question: which additive route should 2K PU clearcoat buyers screen first when the finish is being judged by crater visibility, DOI and gloss hold, or post-cure scratch performance?
That is a distinct page type. It is not just another broad topcoat article. Clearcoat buyers usually care more about surface cleanliness, transparent-film laydown, and how the cured clear layer survives touch and handling after the appearance already looks acceptable.
What 2K PU clearcoat buyers are usually trying to fix
In practical 2K polyurethane clearcoat work, the first bottleneck usually lands in one of these lanes:
- the film is still cratering or wetting unevenly, especially in formulation-sensitive packages where compatibility matters before fine appearance tuning
- the clearcoat reaches the surface but still does not level cleanly enough, so gloss, DOI, or smoothness stay below target
- the cured clear film looks acceptable at first, but the buyer still needs better scratch resistance, abrasion handling, or more confidence around recoating and downstream durability
That is also consistent with general industry framing. Clearcoat programs usually separate wet-stage defect cleanup, visible-film leveling, and post-cure durability before they lock the first additive shortlist. The product facts below stay tied to Longchang-supported product pages and current company-controlled comparison content.
Quick comparison table: which route solves what first?
| Buying factor | CHLUMIAG® 3467 | CHLUMIFE® 3370 | CHLUMIFE® 3307X |
|---|---|---|---|
| Main first-screen job | Compatibility-first anti-cratering, wetting, and broader surface-balance entry | Reactive leveling, gloss, and smooth clear-film refinement in 2K PU systems | Post-cure scratch resistance, abrasion handling, smoothness, and recoat-aware finish support |
| System language supported by Longchang | UV, solvent, and water-based systems, plus polyurethane resin modification | Two-component polyurethane crosslinking systems, hydroxyl topcoats, UV, solvent, water-based, and baking-finish routes | UV and solvent systems, non-water-based route with solvent pre-dilution guidance |
| Strongest supported fit for this page | Formulation-sensitive 2K PU clearcoats where compatibility and crater cleanup matter first | 2K PU clearcoats that need cleaner leveling, gloss hold, and smooth transparent laydown | Clearcoats that already level directionally but still need stronger mar or scratch durability after curing |
| Key supported strengths | Leveling, anti-cratering, substrate wetting, anti-sticking and peeling, scratch resistance, abrasion resistance | Leveling, gloss, smoothness, and direct fit for two-component polyurethane crosslinking systems | Abrasion and scratch resistance after film formation, surface smoothness, leveling, and recoatability priority |
| Important watchpoint | Best used as a compatibility-first route, not as a promise that every clear-finish target will be solved by one additive alone | Should be screened when reactive clear-film refinement is the real target, not when the main problem is still crater rescue | Not a water-based route, and Longchang’s handling logic still points to solvent pre-dilution before use |
When CHLUMIAG® 3467 is the better fit
CHLUMIAG® 3467 should move earlier when the 2K PU clearcoat problem still feels formulation-sensitive. Longchang positions it as a modified silicone additive for comprehensive modification of polyurethane coatings, PU leather, and composite coatings. The same supported route includes leveling, anti-cratering, substrate wetting, anti-sticking and peeling, scratch resistance, and abrasion resistance, plus broader notes around low-temperature flexibility, breathability, and moisture permeability. Longchang also supports it across UV, solvent, and water-based systems with a typical 0.1% to 1.0% addition range.
That makes 3467 the stronger first route when:
- the clearcoat is still showing craters or unstable wetting and the buyer does not want to jump too fast into a narrower finish-only additive
- the project needs a compatibility-first benchmark before the team optimizes DOI or scratch performance more aggressively
- the formulator wants a route that can also sit inside polyurethane-resin-modification logic or broader cross-system development
- the commercial risk is more about whether the clearcoat behaves cleanly enough at the surface interface than about the final scratch number alone
In short, 3467 is the earlier route when the buyer still needs a stable entry into the clearcoat surface window.
When CHLUMIFE® 3370 is the better fit
CHLUMIFE® 3370 belongs earlier when the buyer already knows the project is really about reactive 2K polyurethane surface refinement. Longchang supports it as an organosilicon feel agent and silicone surfactant for two-component polyurethane crosslinking systems and hydroxyl coating systems. The supported performance points include leveling, gloss, and smoothness, with broader applicability across UV, solvent, water-based, and baking-finish systems. The addition range on current Longchang-supported pages is 0.1% to 1.0%.
That makes 3370 the better first route when:
- the 2K PU clearcoat already reaches the surface, but the buyer still wants a cleaner gloss-hold and DOI-style appearance result
- the commercial target is a smoother transparent film rather than a broad compatibility rescue
- the clearcoat line is already clearly inside a two-component polyurethane crosslinking system and the team wants a route directly supported for that lane
- the surface needs to look more refined without jumping immediately to a post-cure durability-first additive
This is why 3370 earns a distinct place on a clearcoat page. It is not just a generic surface additive. It is a reactive clear-film refinement route tied to a specific 2K PU selection story.
When CHLUMIFE® 3307X is the better fit
CHLUMIFE® 3307X deserves earlier review when the clearcoat can already level directionally, but the buyer still needs a stronger answer on scratch resistance after film formation. Longchang supports 3307X around abrasion resistance and scratch resistance of resin films after formation, while also keeping surface smoothness, leveling, and recoatability in the supported selection logic. Current company-controlled content also keeps the product inside a UV and solvent route, with a typical 0.1% to 1.0% addition range and a practical note that it is usually prepared as a solvent solution before use.
That makes 3307X the stronger first move when:
- the clearcoat appearance is mostly acceptable, but the cured film still marks too easily in handling or service
- the buyer needs a clearer scratch or mar-resistance route instead of re-running another wet-stage leveling trial
- surface smoothness and recoatability still matter together in the final finish decision
- the system is already in a non-water-based 2K PU lane where solvent-side handling is acceptable
3307X is not the first tool for crater rescue. It is the earlier choice when the buyer is already looking at the cured clear film and asking whether the finish can stay commercially acceptable after contact, wiping, or handling.
How buyers should choose before requesting samples
1. Decide whether the failure starts before or after the clear film looks acceptable
If the film still shows crater, wetting, or compatibility instability, start earlier with 3467. If the surface reaches the panel but still lacks smooth gloss-hold or DOI-style refinement, 3370 deserves earlier screening. If the clearcoat already looks directionally right but fails after cure, move faster to 3307X.
2. Keep transparent-film watchpoints visible
In 2K PU clearcoats, crater edges, gloss breaks, and mar damage stay visible. That means buyers should not judge the additive shortlist only by whether a panel cures. They should judge whether the transparent film still looks commercially clean after curing.
3. Do not ask one additive to solve crater rescue, final leveling, and post-cure scratch at the same time
Those jobs can influence each other, but they are still different first-screen tasks. Clearcoat development usually gets cleaner faster when the first additive screen matches the stage where the failure actually begins.
4. Keep the system boundary visible
3467 supports broader UV, solvent, and water-based logic plus resin-modification paths. 3370 is directly supported for two-component polyurethane crosslinking systems and hydroxyl topcoats. 3307X sits in a non-water-based UV or solvent route with solvent-side handling guidance. That boundary matters before fine dosage differences matter.
5. Build the first shortlist deliberately
For many buyers, the cleanest first round is one compatibility-first crater route, one reactive clear-film leveling route, and one post-cure scratch route. That usually teaches more than screening three products from the same logic bucket.
Recommended Longchang path from this page
- Compatibility-first 2K PU route: CHLUMIAG® 3467
- Reactive clear-film leveling route: CHLUMIFE® 3370
- Post-cure scratch route: CHLUMIFE® 3307X
- Cluster overview: CHLUMICRYL® Coating and Ink Additives
- Related upstream page: How to Choose Surface Additives for 2K Polyurethane Primers
- Related finish page: How to Choose Surface Additives for 2K Polyurethane Topcoats
- Related function page: How to Choose Leveling Additives for Coatings and Inks
- Related durability page: How to Choose Scratch-Resistant Additives for Coatings and Inks
FAQ
Which additive should 2K PU clearcoat buyers test first when the film is still cratering?
Usually CHLUMIAG® 3467, because Longchang supports it for anti-cratering, substrate wetting, leveling, and broader polyurethane-coating modification logic.
When should CHLUMIFE® 3370 move ahead of CHLUMIAG® 3467?
3370 should move earlier when the clearcoat already behaves directionally at the surface and the main goal becomes reactive leveling, gloss, and smoother transparent-film refinement inside a 2K polyurethane crosslinking route.
Why would CHLUMIFE® 3307X be chosen before another leveling additive?
Because some clearcoat programs are no longer blocked by wet-stage laydown. They are blocked by post-cure scratch resistance, abrasion handling, and finish durability after the film has already formed.
Can one of these three products replace the other two?
No. They belong to different first-screen jobs. 3467 is a compatibility-first crater and wetting route, 3370 is a reactive clear-film leveling route, and 3307X is a post-cure scratch and durability route.
What is the fastest way to shorten the additive shortlist?
Define whether the problem starts at the surface interface, in the visible clear-film laydown, or in the cured clearcoat durability. That usually shows which route deserves the first sample round.
Need a tighter 2K PU clearcoat shortlist?
If your team is stuck between crater cleanup, gloss-hold leveling, and post-cure scratch performance, do not keep asking one additive to solve all three. Split the problem by stage first. That usually makes the CHLUMICRYL® route easier to validate and move toward inquiry.