Expandafoam Closed Cell: Comprehensive Technical Details

Product Overview

Expandafoam Closed Cell is a medium density, closed cell polyethylene foam rod supplied in circular section cords of varying diameters. It is primarily designed as a bond breaker and joint profile former to support elastomeric sealants in expansion joints between all common building materials.

Material Composition & Properties

Physical Characteristics

Expandafoam Closed Cell is manufactured from medium density, closed cell polyethylene foam, which provides the following key properties:

• Form: Compressible, closed cell polyethylene foam rod with circular cross-section
• Color: White
• Nominal Density: 25 kg/m³
• Service Temperature Range: -80°C to +100°C

Performance Features

The closed cell structure of Expandafoam Closed Cell delivers exceptional durability and reliability:

• Water Absorption: Minimal at 0.01 ml/cm³, providing durability in wet conditions
• UV Resistance: Resistant to long-term UV exposure
• Non-Gassing: Does not release volatile compounds
• Migratory Chemicals: Contains no migratory chemicals that could adversely affect joint sealants
• Weathering Performance: Undergoes weathering tests confirming no disintegration occurs
• CFC Free: Manufactured without chlorofluorocarbon compounds

Design & Technical Specifications

Compression Requirements

Expandafoam Closed Cell must be installed under compression to prevent displacement by sealant:

• Compression Ratio: Should be compressed by 25% during installation (or use foam 1/3 larger than the joint size)
• Cross-Section Formation: After proper compression, assumes an oval cross section with depth greater than nominal joint width

Joint Sizing Guide

The diameter of Expandafoam Closed Cell is selected based on joint width using the following specifications:

Joint Width	Expandafoam 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 centre of Expandafoam)
• Minimum Bonding Depth: 6 mm on smooth glass and metal surfaces; 12 mm on porous or rough surfaces
• Joint Face Depth: For larger joints, normally half the joint width

Advantages & Key Benefits

Expandafoam Closed Cell offers multiple advantages for construction applications:

• Compatible with All Elastomeric Sealants: Works seamlessly with all types of elastomeric joint sealants
• Readily Compressible: Easily compressed to accommodate varying joint sizes
• Low Load Transfer: Minimizes stress transfer to adjacent building materials
• Convex Face Profile: The circular section provides optimal shape for elastomeric sealants during joint movement
• Rot Proof: Ensures long-term durability and integrity
• No Water Absorption: Prevents water-related degradation

Applications

Primary Uses

Expandafoam Closed Cell is used as a backing strip and joint filler in diverse construction applications:

Roads, Bridges & Roof Joints

• Backing strip for non-traffic-bearing expansion joints

External Walling & Cladding

• Backing strip for expansion joints
• Gap filler for open joints prior to sealant application
• Low load transfer joint filler in brick infill panel walling

Glazing

• Gap filler and backing strip for perimeter sealing around frames and sub-frames

Internal Finishes

• Gap filler and backing strip around partitions, work tops, and baths
• Support for sealants in partition joints

Bridge Decks & Building Superstructures

• Back-up and bond breaker strip in various structural applications

Product Supply & Material Codes

Expandafoam Closed Cell is available in the following sizes and roll lengths:

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.

Limitations & Restrictions

• Not Suitable for Hot Pour Sealants: Expandafoam Closed Cell cannot be used with hot pour sealants due to material limitations
• Not Suitable for High-Load Applications: For applications where joint backing must provide continual support (such as water retaining structures or traffic-bearing floor joints), Stiffjoint, a semi-rigid filler, should be used instead
• Fitting Care Required: Damage during fitting may allow air voids to form in sealant, compromising joint integrity. Do not use sharp objects when fitting

Installation & Application

Installation Method

• 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
• Ensure the sealing slot is free from mortar droppings, slurry, and other contaminants prior to installation

Installation Outcome

Correct fitting results in an oval cross section with depth greater than nominal joint width, requiring careful attention to ensure correct sealant dimensions are maintained after installation.

Manufacturer & Availability

Expandafoam Closed Cell is manufactured and supplied by Fosroc, a global construction products manufacturer. The product is distributed through authorized distributors such as Parchem Construction Supplies Pty Ltd in Australia. Technical support and documentation are available from the Fosroc website at www.fosroc.com.au.

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References

• [1] Fosroc_Expandafoam_Closed_Cell_TDS.pdf
• [4] Fosroc_Flamex_One_TDS.pdf
• [10] Fosroc_Nitoseal_MS250_TDS.pdf
• [11] Fosroc_Nitoseal_MS400_TDS.pdf
• [2] Fosroc_Nitoseal_PU250_TDS.pdf