Naftoseal® MC-780 Classe B

Aircraft tank and fuselage seal

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
NAFTOSEAL® MC-780 Class B fulfills the requirements of the Airbus Specifications AIMS 04-05-001 and 04-05012.

download NAFTOSEAL® MC-780 Class B technical datasheet  

  • Application Life and Cure Time
    Application Life and Cure Time
    (at 23°C/50% r.H. )
    TypeMin.Application TimeMax.Tack-Free TimeTime to Shore A 30
    MC-780 B - 1/20,5 Std./hours≤ 4 Std./hours≤ 8 Std./hours
    MC-780 B - 11,0 Std./hours≤ 7 Std./hours≤ 10 Std./hours
    MC-780 B - 22,0 Std./hours≤ 14 Std./hours≤ 24 Std./hours
    MC-780 B - 44,0 Std./hours≤ 20 Std./hours≤ 48 Std./hours
  • Typical Physical and Application Properties
    Typical Physical and Application Properties
    Viscosity at
    23°C, Brookfield, Spindel 7
    800 ± 200 Pa.s (B-1)
    1400 ± 300 Pa.s (B-1/2, B-2, B-4)
    (2 Umin/rpm)
    Max. 200 Pa.s
    (10 Umin/rpm)
    Mixing ratio by weight10010
    Mixing ratio by volume1006,2
    Non-volatile content≥ 94% (B-1)
    ≥ 97% (B-1/2, B-2, B-4)
  • Typical Physical and Performance Properties
    Typical Physical and Performance Properties
    Cured Compound after 14 days/23 °C)
    Specific gravity1,1 g/ccm
    Ultimate Shore A Hardness50 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 (%)
    ConditioningTypical Values
    14 days 23 °C≥ 1,5300
    6 months fuel / 23 °C≥ 1,5300
    2. Peel Strength (N/25mm /% Cohesion)
    AdherendConditioningTypical Values
    Al + Epoxy Primer14 days 23 °C
    300 h jet-fuel at 100 °C
    ≥ 120 N/25mm – 100%
    ≥ 120 N/25mm – 100%
    Al + Epoxy + PU Topcoat14 days 23 °C≥ 120 N/25mm – 100%
  • Surface Preparation

    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).

  • Packaging

    The material is supplied in the following containers

    DesignationBase Compound Content/PieceNo./Case
    Techkit 5555 ccm24
    Techkit 130130 ccm24
    Unit 1818 litres
    Unit 162162 litres9 x 18 l Base + 1 x Hardener
  • Storage

    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.