Where Do The Yellow Spots On uPVC Frames Come From?
uPVC Window: Foil Displacement On Spacers & Couplings
Every window maker knows the problem: The decorative film shifts and the customer complaints about extensions & couplings.
What is the cause of the shifts and what can be done about it?
Shifting at the broadening.
Every window manufacturer has certainly experienced this: to the best of our knowledge, we construct window elements with extensions, couplings or corner posts, mounted clean and according to RAL, & then after 1 to 2 years, the customer complains that the decorative film looks like an accordion in places. How can the damage picture be explained & is there an antidote here?
For the reason, there is a simple explanation. The profile manufacturers design their profile geometry according to various requirements, including the fact that profiles can be clipped on at some points or inserted into each other in a snug fit. However, one always starts from (white) unbacked profiles.
Spacers & coupling for bridging a column
The customer does not only want white or coloured profiles, but usually requires foil-laminated surfaces with the corresponding design options.
For this purpose, the white or coloured through profile is laminated & thus changes the cross section.
Commercially available laminating films are approx. 200 to 250 μm thick, & the adhesive bed with approx. 50 μm is added. The profile is therefore where the film is applied by a quarter of a millimetre thicker.
If two profiles come together unfavourably, this results in half a millimetre more, which leads to tensions.
At some point the tension becomes too great
With blunt bumps, as seen in the pictures, another effect is added: The film is pulled around the profile at the factory; after all, no disturbing edge of the base material should be visible.
Now, if the two profiles - mostly frame & widening - screwed, creates pressure on the edge.
Here, the film is trapped & prevented from expanding.
The view side, however, can expand when heated.
At some point the tension becomes too great & the weakest link in the chain, in this case the adhesive layer, breaks off & the typical fold-like throw comes about.
The same effect often occurs along the edge of the glass seal as the film passes behind the seal.
For refurbishment then helps to remove only the films of the visible side & apply a repair film.
What solutions are there for this problem?
Of course, no profile manufacturer will produce two different geometries now, but a few changes in production & planning could significantly reduce the risk of foil shedding.
A solution, also in the name of increasingly frequent yellow discoloration on white profiles, it would generally be good to hide all profiles and modify the profile geometry accordingly.
This would help to solve the problems in the area of couplings or over-pushed profiles.
If the film is no longer glued around the edge of the visible surface, then it cannot be upset.
The second, & according to the author, better approach would be to avoid sticking the foil around the edge of the visible surface.
Many profile manufacturers now do this on the edge of co-extruded or extruded gaskets on glare & casement frames.
Here, a new solution would have to be taken on the outer edge in order to avoid, for example, one-sided laminated white profiles a bright strip on the edge.
This could be either dyed base body or even the painting of the edge, as usual in mitre joints.
This contribution by Claudius Freiberg first appeared in Glaswelt 02/2019.
Claudius Freiberg is a master joiner and ö.buv expert carpenter / cabinetmaker.
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