For sealing expansion joints, precast panels, window glazing, and bridge construction, Open Cell Backing Rod - Round acts as a critical bond breaker to prevent three-sided sealant adhesion. Its open-cell structure accelerates sealant curing by allowing the joint to breathe and cure from both sides, while its non-gassing polyurethane composition eliminates the risk of outgassing bubbles in the sealant layer.
This backing rod is extruded from medium-density, firm orange polyurethane foam. Because the cell structure is open, air and moisture pass through the backing rod to reach the rear of the sealant, initiating a faster, more uniform cure. The open-cell structure also means the rod is highly compressible and can be installed rapidly with any tool without risk of surface-puncture outgassing. If the foam is compressed or nicked during installation, it will not release gas bubbles into the curing sealant. Its low surface strength and shearing capabilities ensure that sealants subjected to dynamic joint movement are not restricted by backing rod adhesion.
Suitable for both internal and external applications on the following substrates:
The backing rod is compatible with cold-applied acrylic, silicone, polyurethane, MS, SPUR, and hybrid sealants. It is also compatible with hot-pour sealants, including silicone, rubber, and asphalt, within specified temperature limits.
Most sealants require a 2:1 width-to-depth ratio. When correctly installed, the backing rod controls the tooling depth so the sealant thickness is half its width. Use of the Backing Rod Insertion Tool (TOOLBACKROD) is recommended to set the backing rod to the correct, consistent depth. If the joint depth is too shallow to accommodate a backing rod, use a bond breaker tape instead to prevent three-sided adhesion.
To ensure proper compression in round joints, select the rod size according to the joint width limits below:
What size backing rod should I choose?
Select a rod about 25% larger than the joint width so it remains compressed in place.
Why use open-cell backing rod?
It controls sealant depth, prevents three-sided adhesion and allows air or moisture access behind curing sealant.
Can it be used with hot-pour sealants?
Do not use above 70°C without confirming suitability with the technical department.
Can it be left exposed?
No. Protect the foam from UV and cover it within the joint system.
| Property | Value |
|---|---|
| Product Type | Polyurethane Foam |
| Density | 32 ± 3.0 Kg/m³ |
| Tensile Strength | 120 < kPa |
| Compression Set | 10 > % |
| Indentation Force Deflection 25 Percent | 340 ± 20 N |
| Elongation | 90 < % |
| Ball Rebound | 50 > % |
| Application Temperature | -40°C to +70°C |
| Service Temperature | -60ºC to intermittent 260ºC |
| Chemical Resistance | Excellent to water, detergent solutions, Moderate diluted acids & alkalis, petrol & oil for short periods |
| Compressibility | 25% nominal at 70 to 100 gms/sq-cm |
| Approximate Density | 64 to 96 kg per cubic meter |
| Shelf Life | 5 years |
| Indentation Force Deflection | 340 ± 20 N |
| Storage Conditions | Cool Dry between 10°C - 35°C, keep out of direct sunlight |
Here are some common examples on where Open Cell Backing Rod - Round used by our customers.
