Millboard – High-Density Ceramic Fibre Boards for Gaskets & Back-up Insulation
High-density millboards from Alkegen® (formerly Unifrax®) – 4 lines (85K / 120K / 85KB / 120WT) for gaskets, back-up insulation & heat shields up to 1100 °C.
SENN supplies Millboards from Alkegen® (formerly Unifrax®) – high-density (910–950 kg/m³), mechanically strong high-temperature boards in four grade lines for industrial high-temperature gaskets, refractory back-up insulation, heat shields, molten-metal transport systems and boiler linings. Service temperatures up to 850 °C (85K, 85KB) or 1100 °C (120K, 120WT). Special lines: Millboard 85KB with biosoluble mineral wool (REACH-friendly up to 850 °C) and Millboard 120WT on a wollastonite base without man-made mineral fibres. Supplied in standard sheet size 1000 × 1000 mm, thicknesses 1–10 mm; cut-to-size and stamped parts per drawing on request.
- Lines available
- Alkegen® Millboard 85K (850 °C, grey) | Alkegen® Millboard 120K (1100 °C, white – standard choice for 1100 °C) | Alkegen® Millboard 85KB (850 °C, grey – biosoluble) | Alkegen® Millboard 120WT (1100 °C, brown – wollastonite base, no man-made mineral fibres)
- Delivery forms
- Standard sheets 1000 × 1000 mm loose / carton / pallet | Cut-to-size per drawing | Stamped parts | Water-jet / laser-cut shapes | Production runs to specification
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Key Benefits
- Four grade lines – 85K, 120K, 85KB, 120WT – for different temperature and regulatory profiles
- High density (910–950 kg/m³) and tensile strength (2.5–3.5 MPa)
- Up to 1100 °C on 120K (ceramic fibre) and 120WT (wollastonite)
- Low thermal conductivity (0.10–0.16 W/m·K at 400–800 °C)
- Biosoluble 85KB – REACH-friendly alternative up to 850 °C
- 120WT without man-made mineral fibres – wollastonite base, low SiO₂ (17.9 %), high Al₂O₃ (44.5 %)
- Easy to fabricate with standard tools – saw, die-cut, water-jet, laser
- Thicknesses 1–10 mm in eight steps (2, 3, 4, 5, 6, 8, 10 mm on all lines; 1 mm only 120WT)
Typical Applications
- Refractory back-up insulation in industrial furnaces, combustion chambers and boilers
- High-temperature gaskets on furnace doors, flanges, access ports, peep-doors
- Heat shields for personnel, operator stations, hot-gas ducts
- Molten-metal transport systems (launders, covers) as back-up insulation
- Boiler linings in biomass, coal and waste-incineration plants
- Stamped parts and water-jet / laser-cut shapes for gaskets, insulation, electrical isolation layers
- Laminations and composite structures (Millboard as rigid core layer)
- Back-up insulation behind firebrick in thin interlayers
- Asbestos millboard replacement in legacy installations
Four Alkegen® Millboard Lines Compared
The millboard lines differ in material base, maximum service temperature, regulatory profile (conventional vs. biosoluble mineral wool, with / without man-made mineral fibres) and colour. Physically they are very similar: comparable density (910–950 kg/m³), similar thermal conductivity and shrinkage behaviour.
Property Millboard 85K Millboard 120K Millboard 85KB Millboard 120WT Material base Mineral wool + ceramic fibre Ceramic fibre Biosoluble mineral wool Wollastonite, no man-made fibres Max. service temperature 850 °C 1100 °C 850 °C 1100 °C Colour grey white grey brown Density 910 kg/m³ 910 kg/m³ 910 kg/m³ 950 kg/m³ Tensile strength 2.5 MPa 3.0 MPa 3.0 MPa 3.5 MPa Al₂O₃ 24.4 % 34.1 % 20.6 % 44.5 % SiO₂ 55.5 % 43.6 % 53.3 % 17.9 % CaO + MgO — 0.9 % 3.7 % 20.2 % Fe₂O₃ + TiO₂ 3.0 % 1.7 % 3.9 % 1.2 % Alkali 1.5 % 1.0 % 1.9 % 0.9 % Organic binder 10.0 % 11.5 % 10.0 % 12.8 % Loss on ignition 17.0 % 19.0 % 18.0 % 16.0 % Linear shrinkage 24 h <2 % at 850 °C <3 % at 1000 °C <2 % at 850 °C <1 % at 1000 °C Thermal Conductivity (W/m·K) – mean temperature
Temperature 85K 120K 85KB 120WT 400 °C 0.10 0.10 0.10 0.12 600 °C 0.11 0.11 0.11 0.13 800 °C 0.13 0.13 0.13 0.16 1000 °C — 0.14 — 0.20 Standard Dimensions & Delivery Forms
Standard sheet size: 1000 × 1000 mm (40 × 40 in).
Available thicknesses (mm) and pack quantities:
- 1 mm – only 120WT – 100 sheets/carton, 1000/pallet
- 2 mm – all 4 lines – 50/carton, 500/pallet
- 3 mm – all 4 lines – 32/carton, 330/pallet
- 4 mm – all 4 lines – 25/carton, 250/pallet
- 5 mm – all 4 lines – 20/carton, 200/pallet
- 6 mm – all 4 lines – 16/carton, 165/pallet
- 8 mm – all 4 lines – 13/carton, 125/pallet
- 10 mm – all 4 lines – 10/carton, 100/pallet
Other thicknesses and dimensions are available on request (subject to minimum order quantity).
Fabrication: sawing, die-cutting, water-jet and laser cutting. Cut-to-size and stamped parts per drawing are supplied for single pieces and production runs alike.
Safety & Regulatory
Millboard 85K and 120K contain conventional ceramic fibre and mineral wool – health, safety and environmental properties including potential hazards, handling precautions and emergency measures are described in the safety data sheet. Read the data sheet carefully before handling, storing or using the product.
Millboard 85KB uses biosoluble mineral wool fibres – REACH-friendly profile up to 850 °C.
Millboard 120WT is manufactured on a wollastonite base and contains no man-made mineral fibres – up to 1100 °C, without RCF / mineral-wool labelling obligations.
The organic binder content (10–13 %) burns off on first heating – provide adequate ventilation.
Related Refractory Boards at SENN
Millboard is the dense, thin form for gaskets, back-up insulation and stamped parts. For thermal insulation in larger thicknesses we supply:
- Fiberfrax® Duraboard® (Alkegen®, formerly Unifrax®) – vacuum-formed high-temperature insulating boards in six lines, 1260–1649 °C, 3–76 mm thickness
- Ceramic Fibre & Aluminosilicate Wool Boards – overview of all board types, fibre classes and supply availability at SENN (incl. Morgan Kaowool®, Ceraboard®, Superwool®)
- GTPS-350 Ceramic Fibre Paper – thin, flexible paper form (0.4–3 mm) for linings and separation layers
Frequently Asked Questions
Which Millboard line for which application?
Millboard 120K is the standard choice for the 1100 °C range – classical ceramic-fibre mix, white, 910 kg/m³, 3.0 MPa tensile strength. Millboard 85K is the conventional mineral-wool / ceramic-fibre mix for up to 850 °C – economical, grey. Millboard 85KB offers the same temperature profile as 85K (up to 850 °C) but with biosoluble mineral wool – REACH-friendly alternative. Millboard 120WT is on a wollastonite base and contains no man-made mineral fibres – 1100 °C, brown, 950 kg/m³, 3.5 MPa – first choice when fibre labelling has to be avoided.
When Millboard and when Duraboard®?
Millboard is the right choice for gaskets, back-up insulation and thin heat-shield covers – high-density boards (910–950 kg/m³), 1–10 mm, up to 1100 °C. Fiberfrax® Duraboard® (also Alkegen®, formerly Unifrax®) is the choice for thermal insulation in larger thicknesses – vacuum-formed, lighter insulating boards (192–419 kg/m³), 3–76 mm, up to 1649 °C. The two products complement each other: Duraboard insulates, Millboard seals and bears mechanical loads.
Is Millboard 85KB really biosoluble and REACH-compliant?
The mineral-wool fibres used in Millboard 85KB are biosoluble according to the manufacturer. This makes 85KB a REACH-friendly alternative to RCF-based millboards in the temperature range up to 850 °C. For temperatures above 850 °C, Millboard 120WT is the alternative: wollastonite base, no man-made mineral fibres. The exact regulatory classification is documented in the current safety data sheet – we provide it on request.
Which sheet sizes and thicknesses are available?
Standard format is 1000 × 1000 mm. Thicknesses: 1 mm (only 120WT), 2, 3, 4, 5, 6, 8 and 10 mm in all four lines. Pack quantities per thickness range from 10 to 100 sheets per carton and 100 to 1000 per pallet (see specification table above). Other thicknesses and dimensions as well as cut-to-size parts, stamped shapes and laser / water-jet cut parts per drawing are supplied on request – subject to minimum order quantity.
Is the Unifrax Millboard still the current product?
Yes. Unifrax® has rebranded to Alkegen® – same company group, same plants, same formulations. Older datasheets still bear the Unifrax logo (e.g. U-126 DE, Rev 0, December 2009); the Millboard 85K, 120K, 85KB and 120WT lines shown there are now marketed as Alkegen® Millboards with unchanged specifications. Current revisions and safety data sheets are provided on request.
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Since 2001, KS Kneissl & Senn Technologie GmbH
has been producing insulation materials and seals for a wide range of applications up to a temperature range of 1600 °C. A diverse range of machinery (CNC 5-axis milling, plotting, punching, sewing, water jet cutting, vacuum forming, etc.) enables us to shape a wide variety of materials for you. The main materials include: glass fibers, aramid fibers, mineral fibers, biosoluble fibers, ceramic fibers, silicate fibers, vermiculite, calcium silicate, microporous materials, elastomers (rubber, silicone, silicone foam, etc.), etc.
The company has been ISO9001 certified since 2009, currently in accordance with the 2015 revision of the standard.
