Expandafoam Closed Cell: Technical Details, Specifications, and Features

Product Overview

Expandafoam Closed Cell is a medium-density, closed-cell polyethylene backing rod supplied in circular section cords of varying diameters. It is primarily manufactured and supplied by Fosroc and distributed through Parchem Construction Supplies Pty Ltd. This product functions as a bond breaker, joint profile former, and backing strip in expansion joints across various building applications.

Key Characteristics

Material Composition

Expandafoam Closed Cell is manufactured from closed-cell polyethylene foam as its primary material component. The foam features a cross-linked structure that provides compressibility while maintaining structural integrity. The product is CFC free, making it environmentally safe.

Physical Properties

The product exhibits the following technical specifications:

Property	Specification
Form	Compressible, closed cell polyethylene foam rod
Color	White
Nominal Density	25 kg/m³
Service Temperature Range	Minus 80°C to 100°C
Water Absorption	0.01 ml/cm³
Weathering Test	No disintegration
Thermal Conductivity	K factor 0.031 WMK at 0°C

Functional Properties

Advantages

• Compatible with all elastomeric sealants – provides optimal support without bonding issues
• Readily compressible – facilitates easy installation and positioning within joints
• Low load transfer – reduces structural stress across joints
• Non-gassing – ensures compatibility with joint sealants
• No water absorption – protects joint integrity and sealant performance
• Non-absorbent – resists moisture uptake
• Rot proof – resistant to biological decay
• Excellent recovery after compression – achieves greater than 90% recovery, enabling repeated use
• Easily cut on-site – can be readily trimmed to required dimensions

Available Sizes and Material Codes

Expandafoam Closed Cell is supplied in circular section cords with the following dimensions and material codes:

Size	Material Code
10mm × 250m roll	FC700973-UNIT
13mm × 100m roll	FC700974-UNIT
15mm × 100m roll	FC700975-UNIT
20mm × 60m roll	FC700976-UNIT
25mm × 50m roll	FC700977-UNIT
30mm × 50m roll	FC700978-UNIT
40mm × 2m strip	FC700979-UNIT
50mm × 2m strip	FC700980-UNIT

Other sizes may be available upon application.

Installation and Design Criteria

Compression Installation Method

Expandafoam Closed Cell should always be installed into a joint under compression to ensure that applying the joint sealant will not displace the foam. This is achieved by compressing Expandafoam Closed Cell by 25% when installing into a joint, or by using foam 1/3 larger than the joint size.

Size Selection Guide

The following guidance chart indicates appropriate foam diameter sizing based on joint width:

Joint Width	Expandafoam Closed Cell Diameter
5 to 8 mm	10 mm
9 to 11 mm	13 mm
12 to 13 mm	15 mm
14 to 17 mm	20 mm
18 to 20 mm	25 mm
21 to 27 mm	30 mm
28 to 35 mm	40 mm
36 to 45 mm	50 mm

Sealant Depth Requirements

• Minimum sealant depth: 6 mm at the thinnest section of the sealant bead (above the center of the foam)
• Minimum bonding depth at joint face: 6 mm on smooth glass and metal surfaces; 12 mm on porous or rough surfaces
• Larger joints: The depth of the joint face should normally be half the joint width

Cross-Section Configuration

When properly compressed and installed into joints, Expandafoam Closed Cell assumes an oval cross section with increased depth compared to its nominal joint width. The circular section of Expandafoam Closed Cell provides a convex face to ensure that applied elastomeric sealants achieve optimal shape for minimum strain as joints move.

Application Instructions

Installation Method

When used as a backing strip, Expandafoam Closed Cell is simply push fitted back into the joint. The cord diameter used should be 20 to 30% greater than the joint width. Installation should avoid the use of sharp objects, as any damage to joint backing may allow air voids to form in applied sealant.

Expandafoam can be fixed into position using suitable general construction adhesive. An optional self-adhesive backing variant is available to facilitate installation without requiring separate adhesive.

Joint Preparation

When used as an expansion or isolation joint filler, Expandafoam Closed Cell should be positioned to provide for a surface sealing slot of required dimensions, ensuring that the sealing slot is free from mortar droppings, slurry, and other contaminants.

Applications

Expandafoam Closed Cell is suitable for use in various building applications:

• Expansion joints between all common building materials
• Roads and bridges – as a backing strip for non-traffic-bearing expansion joints
• External walling and cladding – as a backing strip for expansion joints and gap filler
• Glazing – as a gap filler and backing strip around window frames and sub-frames
• Internal finishes – as support for sealants in partition joints and around work tops and baths
• Brick and blockwork – as an expansion joint filler in building superstructures
• Concrete floors – as a back-up strip for elastomeric sealants in non-traffic-bearing applications
• Panel construction – as a gap filler, back-up strip, and bond breaker in open joints
• Bridge abutments and deck joints – as a hinge joint filler

Limitations

Unsuitable Applications

Expandafoam Closed Cell is not suitable for:

• Hot pour sealants – material compatibility limitations prevent use with this sealant type
• Water retaining structures – where continual joint support is required; Stiffjoint (a semi-rigid filler) should be used instead
• Floor joints subject to traffic – more rigid support is required; Stiffjoint is recommended
• Long-term outdoor UV exposure – the product is not resistant to long-term UV exposure, limiting its outdoor durability

Installation Precautions

• Do not use sharp objects when fitting Expandafoam Closed Cell, as damage to joint backing may allow air voids to form in sealant
• Careful sealant positioning is necessary after fitting to ensure correct sealant dimensions are maintained

Chemical and Environmental Resistance

• Chemical resistance: Resists most common acids and chemicals without degradation
• Migratory chemicals: The product contains no migratory chemicals that could adversely affect sealants
• Non-gassing property: Ensures compatibility with joint sealants
• Weathering resistance: Exhibits no disintegration when subjected to weathering tests

Documentation and Safety

A Safety Data Sheet (SDS) and Technical Data Sheet (TDS) are available from the Fosroc website (www.fosroc.com.au). Both documents should be read carefully prior to use, as application or performance data may change over time.

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References

• [1] Fosroc_Expandafoam_Closed_Cell_TDS.pdf
• [6] Fosroc_Flamex_One_TDS.pdf
• [16] Fosroc_Expandafoam_TDS.pdf