Aluminum Extruders Provide a Thermal Barrier
Because aluminum is such an effective heat conductor, thermal breaks are typically employed in applications such as exterior windows, doors, or supermarket coolers to insulate the "cold" space from the "warm" space.
Extruders commonly offer two thermal break alternatives:
A "pour & debridge" system in which a polyurethane liquid is allowed to harden in a "pocket" designed into the extrusion. The aluminum forming the pocket is then removed to allow the hardened polyurethane to act as an insulator.
A polyamide strip system where a rigid polyamide strip is mechanically crimped between two extrusions designed to accept the strip—thus creating the insulator.
Pour and Debridge Thermal Barrier
Creation of a thermal barrier using Pour & Debridge is a 3-step process:
- Prepare: The aluminum profile is extruded with a strategically placed channel to encapsulate an insulating polymer. The channel surface is conditioned with special equipment to create a "mechanical lock"
- Pour: A two-part polymer is dispensed into the channel as a liquid, then hardens into a strong, structural insulating element
- Debridge: The metal "bridge" is mechanically removed from the bottom of the channel, eliminating the conductive aluminum element and producing a non-metal-to-metal thermal barrier
Polyamide Strips Thermal Barrier
Structural insulating Polyamide Strips have been utilized for thermally breaking aluminum extrusion assemblies for over 30 years and have been in use in North America for over a decade. Strips are available with a variety of configurations to meet differing performance requirements. Creating a thermal break using a Polyamide Strip system involves 3 steps:
- Profile knurling: A knurling wheel is used to produce "teeth" between 0.15 mm and 0.30 mm long in a pocket of the inner and outer extruded profiles that will be joined by the Strip to comprise the frame. These "teeth" will bite into the Strip during the crimping process and insure adequate shear strength for the composite profile.
- Strip insertion: Typically, the Polyamide Strip is pulled or pushed into the extrusion profile, using specialized equipment. However, manual insertion can also be used, and there are assembly methods that pull or push the profile onto the Strip. The preferred method is up to the installer.
- Crimping: Three sets of wheels rotate the extrusion onto the Strip and mechanically lock the components together. Over 1300 pounds of pressure is applied in stages, and the resulting aluminum/Strip assembly will then act as a load-bearing composite. Shear testing is typically conducted periodically to verify that the process has produced an assembly that will perform structurally as required.
