Creep or hydrolysis of the adhesive. I believe these structures are typically acrylic plastic.
Our local aquarium has a 35 foot x 85 foot viewing window. It's 12 inches thick and supposedly built to withstand a 9.0 earthquake. The plastic used is glass reinforced which would certainly help control creep.
The aquarium required 41 of our Higly Engineered Acrylic panels – 26 panels for the outside cylinder and 15 panels for the inside – and 16 on-site bonds ...
There was speculation on Reddit that the cold weather in Berlin and the legal requirement to keep indoor temperatures down (to 16°C) was too much for the (~25°C saltwater) tank. It was allegedly also remodeled in 2020, though in what way is unclear.
The Monterey Bay Aquarium did some remodeling some time back on their big acrylic tank. Apparently they are lined with glass tiles thar were falling off.
Tug:
Acrylic (PMMA) is recyclable, unless it's the cast, crosslinked version.
Problem is it's not commercially viable due to lack of recycled market.
Acrylic is used (mainly) for transparent items.
Chopped up cast acrylic is good for cleaning injection moulding machine barrels though. Used to use quite a bit of it.
Politicians like to panic, they need activity. It is their substitute for achievement.
At the Monterey Bay Aquarium that monster window was done by a Japanese firm using a proprietary method that had them boot everyone out and then they covered up the process with tarps so it couldn't be observed.
Probably two guys with some Tap Plastic drippy bottles.
Well, IF the seams turn out to have been a contributor to this failure, all the companies may feel more pressure to subject their proprietary joining methods to more scrutiny.
