The insulation characteristics of window systems are largely defined by the function of thermal break profiles which create a thermal barrier for heat transfer between parts like window frames. With Promix Solutions' Microcell Technology, thermal break profiles are physically foamed through the controlled addition of atmospheric gases, enabling a further improvement in insulation performance.
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In building and construction applications, this “thermal bridge” prevents heat from entering or leaving the building by means of an increased insulation performance resulting in energy efficient constructions with an improved carbon footprint. This feature is particularly important in areas with large temperature fluctuations and very cold winters and / or hot summers.
In particular, aluminium windows would benefit from a special design where the flow of heat is interrupted, due to the good heat conduction of metals in general. This results in overly cold windows in winter and excessively hot windows in summer. A lot of energy is wasted to maintain a comfortable internal temperature.
Thermal break profiles made of polyamide are used to separate the inner and outer window profiles. Typically, a glass-fibre-filled solution is used to ensure sufficient mechanical stability in the window frame, withstanding significant force, e.g. in high-rise buildings. Polyamide with 25% glass fibers has an insulation value of lambda = 0.40 W/(m-K), which is > 400 times more efficient for thermal insulation vs aluminum, which has a lambda value of about 160 W/(m-K).
To reduce heat transfer, one thermal bridge is sufficient; hence, further reducing the insulation properties of thermal break profiles is a useful approach to gain energy efficiency. This has been achieved in the industry, leading to a next generation of lower lambda value thermal break profiles. With the same material selection, profiles are now physically foamed to generate a microcellular cell structure made from atmospheric gases like nitrogen or carbon dioxide.
The density of the polyamide composite in these profiles is reduced from 1.31 kg/dm³ to 1.0 ± 0.1 kg/dm³, and the lambda value is further lowered to about 0.20 W/(m-K).
Due to the microcellular structure, the profiles' mechanical properties are comparable to those of rigid ones, but with significantly improved insulation between the aluminium profiles, setting a new industrial performance standard.