NAFTOSEAL MC-780 Class B is a two-component, manganese-dioxide cured, low density, liquid polysulphide polymer system providing excellent fuel tank and fuselage seals. It has outstanding resistance to aviation gasoline and jet fuel, as well as resistance to the chemicals and petroleum products used in the aircraft industry.
MC-780 Class B maintains its flexibility and bond strength on most metal substrates like aluminium, stainless steel, steel, titanium and many coatings under extremes of temperature, weathering and stress.
The mixed compound is a thixotropic paste easily applied by extrusion, injection gun or spatula. It has excellent tooling properties.
- Sealing fuselages
- Sealing fuel tanks
Application Life and Cure Time
Application Life and Cure Time (at 23°C/50% r.H. ) Type Min.Application Time Max.Tack-Free Time Time to Shore A 30 NAFTOSEAL® MC-780 B - 1/2 0,5 Std./hours ≤ 4 Std./hours ≤ 8 Std./hours MC-780 B - 1 1,0 Std./hours ≤ 7 Std./hours ≤ 10 Std./hours MC-780 B - 2 2,0 Std./hours ≤ 14 Std./hours ≤ 24 Std./hours MC-780 B - 4 4,0 Std./hours ≤ 20 Std./hours ≤ 48 Std./hours
Typical Physical and Application Properties
Typical Physical and Application Properties base hardener color grey brown Viscosity at
23°C, Brookfield, Spindel 7
800 ± 200 Pa.s (B-1)
1400 ± 300 Pa.s (B-1/2, B-2, B-4)
Max. 200 Pa.s
Mixing ratio by weight 100 10 Mixing ratio by volume 100 6,2 Non-volatile content ≥ 94% (B-1)
≥ 97% (B-1/2, B-2, B-4)
Typical Physical and Performance Properties
Typical Physical and Performance Properties (of
Cured Compound after 14 days/23 °C)
Color: grey Specific gravity 1,1 g/ccm Ultimate Shore A Hardness 50 max. Service Temperatures –55°C / +130°C
Typical Values of MC-780 Class B
Typical Values of MC-780 Class B 1. Tensile Strength (N/mm2) / Elongation (%) Conditioning Typical Values N/mm2 % 14 days 23 °C ≥ 1,5 300 6 months fuel / 23 °C ≥ 1,5 300 2. Peel Strength (N/25mm /% Cohesion) Adherend Conditioning Typical Values Al + Epoxy Primer 14 days 23 °C
300 h jet-fuel at 100 °C
≥ 120 N/25mm – 100%
≥ 120 N/25mm – 100%
Al + Epoxy + PU Topcoat 14 days 23 °C ≥ 120 N/25mm – 100%
To obtain good adhesion, clean surfaces with appropriate cleaners (e.g. Chemetall’s Ardrox® products) to remove dirt, grease and processing oils just prior to sealant application. Use lint-free rags or paper towels that are free of oil. Always pour cleaner on the cloth to avoid contamination of the cleaner supply. Clean one small area at a time, quickly wiping it dry before the cleaner’s solvent evaporates to prevent redeposition of oil, wax or other contaminants. Usually, in the case of most epoxy resin primers, surfaces need not be additionally prepared with an adhesion promoter to improve adhesion. PUR and EP topcoats as well as composite components should be pre-treated by the NAFTOSEAL MC-115 Adhesion Promoter.
Cleaning of Equipment
Immediately after use or before the sealant cures, wash equipment and tools with a solvent.
NAFTOSOLV FN will completely dissolve uncured, semi-cured and fully cured NAFTOSEAL sealants. It provides a method for completely removing NAFTOSEAL and other polysulphide sealant contamination (see separate Data Sheet).
The material is supplied in the following containers
Packaging Designation Base Compound Content/Piece No./Case Techkit 55 55 ccm 24 Techkit 130 130 ccm 24 Pail #colspan #colspan Unit 18 18 litres Unit 162 162 litres 9 x 18 l Base + 1 x Hardener
The shelf life of NAFTOSEAL MC-780 Class B is 6 months from date of manufacture, when stored at temperatures below 26 °C in its original unopened container. Storage at lower temperatures increases shelf life.