Aluminized mylar "space blanket" as shielding material - Page 1
Forum section: electronics / projects

author: ChristofferB
author_rank: Frequent Contributor
timestamp: December 01, 2019, 01:54:43 pm
content: Hey all!I'm currently messing with a few particle detectors, mainly to explore femtoampere/ultra high impedance prototyping stuff, and wanted to assess commercial 'space blankets' as window material. hopefully it would be thin enough to let through most low-energy particles, but conductive enough to mitigate electrical noise in the detector. Also ideally it is gas-impermeable enough to be able to pressurize the chamber slightly.So which side is conducting, again?Neither! if a simple multimeter is to be trusted. But it might still be conductive enough to have some shielding capability.The question is now: which side is aluminized. I cut two pieces of the material, put them on a level surface with either side up and put a few drops of dilute sodium hydroxide on each. Sodium hydroxide (NaOH) dissolves aluminium fairly rapidly, so ideally, one would lose its metal sheen fairly quickly.The results were.. confusing.The silver side out sees no attack after 15 min.The amber side out turns completely transparent in the same time interval. But the amber color remains!If you look carefully at the amber area, a small flake of translucent plastic can be seen.What I think happens is that the base mylar material that aluminum is vapor deposited on is the "silver" side.An amber layer of some film is then laid on top of the aluminum, for whatever reason.So my conclusion is that the structure is something like[[[[[[[[[[[[[[[[[[[[[[[[ <-MYLAR (COLORLESS)//////////////////////// <-ALUMINIUM]]]]]]]]]]]]]]]]]]]]]]]] <-POLYMER FILM (AMBER)This makes the blanket useless as a conducting film, but might still provide some shielding, as the combined film can still couple capacitively to a earthed can.I'm unsure to what degree this will work, though.Hope this helps someone some time some where!--Chris

author: SeanB
author_rank: Super Contributor
timestamp: December 01, 2019, 05:08:17 pm
content: You need a protective film for the sputtered aluminium, so having a coat over it is needed, and probably for your use it is the gold coloured coat. Generally the manufacturers calendar a second film to the sputtered surface for protection, and for any particular manufacturer you will have to find out exactly who made it, the actual part number and then the datasheet, which will give an idea as to how it is laid up. Best is to look at 3M for datasheets on their products, and see if you can get a few evaluation samples to try, as that will answer all the questions on gas permeability, thickness of the coating, the shielding effectiveness and also how to connect to the inner resistive layer.

author: ChristofferB
author_rank: Frequent Contributor
timestamp: December 01, 2019, 08:17:26 pm
content: That might be a good solution, but the point of this was mostly just to see if a cheap mass-produced item like this, could be used without modifications for scientific instruments. It would still be nice to actially access the resistive layer, but i suspect the metallization on low-cost commercial films are very light.