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For expansion joints, window glazing, precast panels, and bridge construction where three-sided sealant adhesion must be prevented, Adheseal Backing Rod Closed Cell - Round provides the essential depth control and bond-breaking foundation. This flexible, low-density white polyethylene foam rod establishes the correct joint profile so cold-applied sealants can function under expansion and contraction cycles.
How it works
Most cold-applied sealants (including acrylic, silicone, polyurethane, MS polymer, SPUR, and hybrids) do not adhere to closed-cell polyethylene. Placed into the joint, this backing rod acts as a bond breaker, forcing the sealant to adhere only to the side walls (two-sided adhesion) and preventing three-sided adhesion which causes premature joint failure. The round profile shape helps the applied sealant form a 2:1 width-to-depth ratio, allowing optimum movement capability. Because of its closed-cell structure, the foam maintains minimal water absorption, making it suitable for damp horizontal joints.
Numbers that matter
- 95% recovery: High resilience ensures the foam returns to its profile and maintains joint pressure after compression cycles.
- 25% compression: Nominal compressibility allows the rod to be compressed into irregular joint widths while remaining firmly in place.
- -40°C to +70°C application limits: Temperature threshold covering the application range of typical cold-applied construction sealants.
- 0.032 g/cm³ density: Low-density polyethylene structure (tested to ASTM D3575) that balances flexibility with structural support for tooling sealants.
Where to use it
Suitable for internal and external joints behind cold-applied sealants over a wide range of construction substrates, including:
- Masonry, brick, stone, and porcelain
- Metal and aluminium
- Timber
- Plastics and fibreglass
- Painted surfaces
- Rubber
- Powder coat
- Waterproof membranes
Installation limits
- Do not UV expose: Must be fully covered by the sealant layer; not suitable for prolonged exposure to direct sunlight.
- Chlorine limits: Not suitable for internal swimming pools where chlorine levels exceed 5ppm.
- Temperature limit: Do not use as a backer where sealant is heated and applied at temperatures above +70°C. For hot-poured sealants, consult the technical department for heat-resistant options.
- Avoid stretching: Excessive longitudinal stretching during installation can damage the rod and alter its nominal diameter.
- Prevent outer skin damage: Avoid puncturing or tearing the outer surface of the rod during installation; damaging the skin can release trapped air, causing bubbles or gas pockets to form in the curing sealant.
- Sizing rule: Select a backing rod size approximately 25% larger than the joint width to ensure sufficient friction to keep the rod in place during sealant application.
- Depth restriction: Where the joint depth is too shallow to accommodate a backing rod, use a bond breaker tape to prevent three-sided adhesion.
Application and tools
The joint must be filled completely, taking care not to trap air. To ensure the backing rod is set to the correct, consistent depth without puncturing the foam skin, the use of the Backing Rod Insertion Tool (TOOLBACKROD) is recommended.
What size closed-cell backing rod should I use?
Select a diameter about 25% larger than the joint width.
Why is the outer skin important?
Puncturing closed-cell foam can release trapped gas and create bubbles in the curing sealant.
Can it be used above 70°C?
No. Use a heat-resistant backer system specified for hotter sealant applications.
Can it be used in chlorinated pools?
It is not suitable for internal pool joints where chlorine exceeds 5ppm.
- Concrete, masonry, brick and stone joints.
- Metal and aluminium joints.
- Timber, plastics and fibreglass interfaces.
- Painted and powder-coated construction surfaces.
- Compatible waterproofing membrane details.
Adheseal Backing Rod Closed Cell - Round Physical Properties
| Property | Value |
|---|---|
| Density | 0.032 g/cm³ |
| Tensile Strength | 3.2-4.5 kg/cm² |
| compression_set | 0.56-8.0 kg/cm² |
| Elongation | 50% |
| Thermal Conductivity | 0.040 W/m.k |
| Application Temperature | -40°C to +70°C |
| Service Temperature | -40°C |
| Tear Strength | 2.7 kg/cm |
| Shelf Life | 5 years, when stored in cool dry conditions between 10°C and 35°C |
| Chemical Resistance | Excellent to water and detergent solutions; moderate to diluted acids, alkalis, petrol, and oil for short periods |
| Compression Set | 0.56 8.0 Kg/cm2 psi |
| Compressive Strength | 0.56 8.0 Kg/cm2 psi |
| Storage Conditions | Cool Dry between 10ºC and 35ºC keep out of direct sunlight |