LBR21811
LBR21811 2K polyurethane isolating sealer for MDF
Two-component polyurethane isolating sealer for MDF, made by Milesi. Goes on as the first coat over bare MDF of any density, especially routed edges and profiles: it seals thirsty edges and faces and evens out absorption so the following white/coloured PU primer doesn't soak into the board or sink on the routing. Good wetting, fast drying, sands very well, holds on verticals (thixotropic). Interior use only.
- Sealing MDF edges and faces (incl. routed cabinet doors) before PU primer
- Cutting consumption of the expensive white/coloured primer on MDF
- Reducing sink-back of the finish on edges and profiles
- Furniture and cabinet doors — interior only
Mix calculator
Ask about LBR21811
Answers are based on the LBR21811 data and the products it mixes with.
Mixing matrix
- % by weight: 40 %official% by volume: 45 %official
Standard ratio from the official page. LNB77 is the main hardener (every dealer pairs it).
Fixed ratio, not a range. Stir the base thoroughly before adding hardener (high solids, it settles); mix at least 60 s after adding it.
- LNB77Hardener% by volume: 48.1–50 %dealer
Polish distributor's shop-floor ratio: 2:1 by volume (1000 ml LBR21811 + 500 ml LNB77). They quote the Milesi TDS as 48.1 % by volume.
Differs from the official 45 % by volume on t-color.ru; in Russia stick to 40 % by weight / 45 % by volume.
- LNB77Hardener% by volume: 40 %dealer
Polish shop WIR: 'LNB 7' (typo for LNB77) at 40 % of base volume.
Probably a weight/volume mix-up; go by the official 40 % by weight.
- % by weight: 10–40 %official% by volume: 15–50 %official
LZC8643 is officially the 'slow PU thinner' (heat above ~25 °C, large parts). LZC1051 is the plain 'PU thinner' (normal); LZC1026's evaporation rate isn't officially stated (the Polish distributor uses it as the standard thinner). Tip (not from a source): low end for a heavier edge-sealing coat, high end for a thin soaking coat.
LZC8643 is officially the 'slow PU thinner'; LZC1051 is the 'PU thinner'. LZC1026 has no official page.
- LZC1026Thinner% by volume: 20–30 %dealer
Polish distributor's practice: 1000 ml base + 500 ml LNB77 + 200–300 ml LZC1026, depending on temperature.
- LZC1026Thinner% by volume: 20 %dealer
| Role | Material | % by weight | % by volume | When |
|---|---|---|---|---|
| Hardener | LNB77 / LNB42 | 40 %official | 45 %official | Standard ratio from the official page. LNB77 is the main hardener (every dealer pairs it).Fixed ratio, not a range. Stir the base thoroughly before adding hardener (high solids, it settles); mix at least 60 s after adding it. |
| Hardener | LNB77 | — | 48.1–50 %dealer | Polish distributor's shop-floor ratio: 2:1 by volume (1000 ml LBR21811 + 500 ml LNB77). They quote the Milesi TDS as 48.1 % by volume.Differs from the official 45 % by volume on t-color.ru; in Russia stick to 40 % by weight / 45 % by volume. |
| Hardener | LNB77 | — | 40 %dealer | Polish shop WIR: 'LNB 7' (typo for LNB77) at 40 % of base volume.Probably a weight/volume mix-up; go by the official 40 % by weight. |
| Thinner | LZC1026 / LZC1051 / LZC8643 | 10–40 %official | 15–50 %official | LZC8643 is officially the 'slow PU thinner' (heat above ~25 °C, large parts). LZC1051 is the plain 'PU thinner' (normal); LZC1026's evaporation rate isn't officially stated (the Polish distributor uses it as the standard thinner). Tip (not from a source): low end for a heavier edge-sealing coat, high end for a thin soaking coat.LZC8643 is officially the 'slow PU thinner'; LZC1051 is the 'PU thinner'. LZC1026 has no official page. |
| Thinner | LZC1026 | — | 20–30 %dealer | Polish distributor's practice: 1000 ml base + 500 ml LNB77 + 200–300 ml LZC1026, depending on temperature. |
| Thinner | LZC1026 | — | 20 %dealer |
Percentages are per 100 parts of component A.
Characteristics
- Solids · Options
- 61 ± 1 % (basis not stated; presumably part A as supplied), ≈ 50 %
- Viscosity
- 60 ± 2 sdealer
- Thixotropy · Options
- yes, excellent vertical hold, does not run off vertical edges at 2:1 by volume
- Drying · Sand or stack · Options
- 0.5, 0.5–1 h, 0.5, 0.5–0.67 h
- Drying · Recoat with primer (min)
- 30 mindealer
- Drying · Fast drying
- good drying speedofficial
- Drying · Conditions
- 18–22 °C (dealer)
- Pot life · Options
- 3 h, 4 h
- Sandability
- sands very wellofficial
- Wetting
- good wetting, very even absorptionofficial
- Compliance
- EN 71-3 (safety of toys — migration of certain elements)dealer
- Interior or exterior
- interior onlydealer
Application
Conventional spray
- Nozzle
- 1.4–2 mmdealer
- Pressure · air
- 2.5–3.5 barrecommended
- Spray viscosity
- 18–24 s DIN4 (4 mm cup), 20 °Crecommended
- Consumption
- 130–150 g/m²official
- Wet film
- 110–125 µmrecommended
- Coats
- one full wet coat laid in two passesdealer
- Recoat
- primer after 30 min at 18–22 °C; if priming later than 3 h, scuff with P320 firstdealer
- Sanding between coats
- P320 on a sponge, light denib to knock off raised fibre, then dust off thoroughlydealer
Aim at the edges and routed profiles — that's where the sealer matters. The white tint shows where you've already covered.
HVLP
- Nozzle
- 1.7–2 mmrecommended
- Pressure · air
- 2–2.5 bar at gun inlet, trigger pulledrecommended
- Spray viscosity
- 18–22 s DIN4, 20 °Crecommended
- Consumption
- 130–150 g/m²official
- Coats
- one full wet coat in two passesdealer
Gun distance 15–20 cm, 50 % overlap. On a 1.5 mm tip only if thinned to the top of the range and you accept less build.
Airmix (air-assisted airless)
- Nozzle
- 0.23–0.33 mm (tip 09–13 thou, 20–40° fan)recommended
- Pressure · fluid
- 40–80 barrecommended
- Pressure · air
- 1–2 barofficial
- Spray viscosity
- 25–35 s DIN4, 20 °Crecommended
- Consumption
- 130–150 g/m²official
Method confirmed by the dealer (Airmix); settings are an engineering estimate.
Airless
- Nozzle
- 0.28–0.33 mm (tip 11–13 thou)recommended
- Pressure · fluid
- 100–150 barrecommended
- Consumption
- 130–150 g/m²official
Large flat parts only; easy to overload routed profiles.
Process and compatibility
- Goes over
- bare MDF
- Temperature and humidity
- 18–25 °C, RH 50–70 %recommended
- Don'ts
- Don't heavily thin the white primer as a substitute for an isolant
- Not for exterior use
- Don't spray over dusty or greasy MDF
- Don't use the mix past its 3 h pot life
- Don't leave it more than 3 h before priming without a P320 scuff
Storage
- Packaging · Options
- 25 л (арт. LBR21811/25), original pack 25 kg
- Storage temperature
- 5–30 °Crecommended
Safety: Flammable solvent-borne product; LNB hardeners contain isocyanates. Spray in an extracted booth, wear an A2P2 respirator (or air-fed), nitrile gloves and eye protection. Keep away from ignition. (Generic 2K PU practice — no SDS found.)
Sources
Value tags: “official”, “dealer”, “catalog”, “schedule” are Technocolor data; “workshop” is from our own datasheets; “recommended” is our engineering estimate (hover to see the reasoning).
- official page: properties, spray 130–150 g/m², hardener LNB77/LNB42 40 % wt / 45 % vol, thinner LZC1026/LZC1051/LZC8643 10–40 % wt / 15–50 % vol
- t-colormarket.ru search: listed as 'LBR21811 Грунт полиуретановый изолирующий для МДФ', manufacturer MILESI; detail page 404
- Holzcom dealer: viscosity 60 ± 2 s ВЗ-6, solids 61 ± 1 %, interior, 25 L pack, LNB77 40 wt / 45 vol
- Blow Lignal (PL Milesi distributor) product page: 2:1 vol with LNB77, LZC1026, pot life ~4 h, sand 30–60 min, pneumatic/airless/airmix, interior only
- Blow Lignal technologist test article: surface prep, 2:1 vol, LZC1026 20–30 % vol, ~50 % solids, 3 h pot life, 1.4–2.0 mm nozzle, one heavy coat in two passes, ready in 30 min at 18–22 °C, P320 denib, LBR608 over it
- WIR Białystok shop product card (PDF): thixotropic, sandable after 30 min, LNB77 40 % vol, LZC1026 20 % vol, 25 kg pack, EN 71-3
- official application methods page (airmix air 1–2 bar, airless up to 200 bar)
Not covered by the sources
- No official Milesi/Technocolor TDS or SDS PDF found for LBR21811 (dealer cites a Milesi TDS figure of 48.1 % vol hardener that is not public)
- t-colormarket.ru product page 404 (item listed in search only) — no 'Все технические характеристики' block: no official dealer solids/viscosity/pot life/drying
- Solids conflict: 61 ± 1 % (timb.ru) vs ≈ 50 % (blowlignal.pl)
- Pot life conflict: 3 h vs ~4 h (both blowlignal.pl)
- Hardener by volume conflict: official 45 % vs dealer 2:1 (50 %) / 'TDS 48.1 %' / WIR 40 % vol
- Dust-free, touch and full-cure times not published
- Density of part A and of the mix not published
- Shelf life not published
- No official spray nozzle/pressure data (conventional 1.4–2.0 mm is dealer; HVLP/airmix/airless settings are derived)
- LNB77, LNB42 and LZC1026 have no official t-color.ru product pages in the local source set
- Not used in any official t-color.ru finishing schedule (the MDF PE+PU schedule uses PTS71 as isolant instead)
- Not in the 2025–2026 Technocolor catalog transcripts