Polyamide Thermal Break Strip in Aluminium Profiles

What it is

A glass-fibre-reinforced polyamide bar rolled mechanically into two separate aluminium extrusions, joining them into one profile while breaking the metal path between inside and outside.

It is structural. The window's strength depends on the strip and on how well it was rolled in.

Specification at a glance

Property	Typical specification
Material	Polyamide 66, approximately 25% glass fibre
Standard	EN 14024 for mechanical performance
Depth	14mm — 34mm and above; state it
Shape	Straight bar, or shaped for higher performance
Assembly	Knurled, inserted and roll-crimped
Verification	Shear test on the assembled profile

Why the rolling process matters

The strip is held by mechanical crimping of the aluminium around it. If the knurling is shallow, the rolling pressure wrong, or the profile tolerance out, the composite fails in shear — the two aluminium halves move relative to each other under load or temperature.

That failure shows up as a window that racks, a sash that stops closing, or sealant joints that tear. It is not visible at handover.

EN 14024 exists to verify exactly this, and the certificate should be for the profile as assembled, not for the strip as supplied.

Where projects go wrong

• Strip depth unspecified, so the U-value in the compliance calculation does not match what was installed.
• Thermal break omitted entirely on air-conditioned buildings, then condensation blamed on the HVAC design.
• Poor rolling quality from a fabricator without the right line.
• Mixing broken and unbroken profiles in one system, leaving a cold bridge at the weakest member.
• Shear certificate for the strip alone, which proves nothing about the assembled profile.

Standards referenced

Thermal barrier profile mechanical performance under EN 14024. Fenestration U-value targets under ECBC 2017. Aluminium sections under IS 733.