Selleys N Mastic is a non-hardening, waterproof sealing putty designed for a wide range of applications where long-lasting flexibility is crucial. Ideal for sealing joints, gaps around windows, and roofing, it ensures that structures remain protected from water ingress. The unique formula remains pliable, making it perfect for environments where movement and expansion are expected.

Whether you're sealing an outdoor roof gutter, securing window frames, or filling gaps in an air conditioning system, Selleys N Mastic provides a professional-grade finish with no cracking or crumbling. The product is also suitable for metal, glass, concrete, and brick, making it a versatile solution for residential, commercial, and industrial projects.

N-Mastic is a non-skinning polybutene-based compound. It will remain permanently soft and paste-like.

Uses
N-Mastic is suitable for sealing concealed lap joints between plastics, metals, timber, glass, masonry, and expanded foam panels.

It may be used in the installation of cool rooms, prefabricated construction and gasket sealed windscreens to exclude draughts and water penetration through joints in materials.

Technical Features
Non-hardening – remains permanently flexible to provide a lasting seal
Good adhesion – adheres well to most substrates
Moisture resistance – provides an excellent barrier to moisture vapour
Microbe resistance – resists microbial attack
Low shrinkage – avoids the risk of sealant pulling away from joint surfaces
Wide service temperatures – withstands –40oC to +80oC service conditions

Application Tips
Due to the non-skinning, non-hardening nature of the sealant, N-Mastic should not be used in exposed joints where dirt pick-up or hand contact can be a problem.

As N-Mastic is not elastomeric, it should not be used in areas subject to considerable dynamic stress.

Although N-Mastic is resistant to static pressures, a curing sealant is recommended where this is a critical factor.

N-Mastic is not recommended for sealing lap joints in mobile homes, truck bodies, etc., as significant vibration and flexing occur during travel.

Technical Details and Performance
Indicative information only, not to be used for setting specifications.

Colour
Off White

Specific Gravity
1.4g/mL

Consistency
Non-sag

Slump (MIL-S-8802, @ 32oC )
2.5mm maximum

Viscosity (Brookfield HAF 7/2 @ 25oC )
10,000 – 14,000 Poise

Flash Point
85oC

Storage Life (25oC )
Indefinite

Packaging
Plastic cartridge (410g)

Performance Properties
Shrinkage (% maximum) 5

Service Temperature
–40oC to +80oC

Life Expectancy
Up to 20 years

Clean Up
Sealant may be removed with a cloth dampened with kerosene or mineral spirits