High Voltage Forum
Electromagnetic radiation => Light, Lasers and Optics => Topic started by: klugesmith on November 09, 2019, 06:38:53 PM
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I want to bond some clear Mylar film to itself, and UV-cured glue seems like a thing to try.
The ideal material would have low viscosity, and not cure too fast from pressure or exposure to air.
The closest thing available at hardware store is "ZAPIT" from Superglue company.
https://supergluecorp.com/product/zap-it/
Comes with a curing light in the form of a little key-chain illuminator, with 1 LED and room for 1 coin-shaped battery. At first glance that's laughably small and low in radiant power. At the opposite extreme are UV radiators for curing ink in continuous printing presses, that roll at many meters per second.
Package says the user is in control. :-) If you skip the UV light, the glue cures anyway within 1 or 2 minutes. Sounds like a bug, not a feature.
Anybody here have a better suggestion?
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I know that we (at least used to) use Loctite 4305 at work. This is UV cured cyanoacrylate but also cures with moisture or just with age in the bottle, so may be along the lines of the one you've already found.
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A company I worked for used a lot of UV cured glue - but acrylic based, not cyanoacrylate. The issue with cyano glues is blooming. Not a single one we tried was truly free of blooming, and for an optical system its just not usable.
The acrylics come in a wide range of viscosities, from watery to paste-like, and will not cure until hit with UV. Best wavelengths vary - we used 365nm as it is less prone to issues with oxygen inhibition, but anything 400nm or shorter usually works. You're right about the pissy little UV light - more power is definitely better.
There are also silicones - used for LEDs, and glue with a heat post-cure to set anything not hit with UV.
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I use an unfocused bluray laser pointer (10-20mW is sufficient) with an expending lens attached, it cures in a couple seconds... just use googles for not getting blind... dirt cheap and efficient
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Nice idea about Blu-ray laser.
What I ended up using (for pancake coils wound on one side of an acrylic sheet)
was a bundle of three UV LEDs, on a long twisted-pair wire from benchtop power supply.
Same kind as shown in "IR wavelength measurement" thread a couple months ago.
I bet many readers have dental fillings made of white resin putty, cured with blue light.
Have learned that popular products use a photo-initiator chemical that responds to blue, not UV.
Coming up soon: pictures of some blue curing lights that I got at a swap meet.
Had not expected to find a semiconductor-free design, which includes:
* MR11 halogen lamp, 50 watts (?)
* Blue-transmitting glass optical filter
* Compact cooling fan
* Light guide made from bundle of optical fibers.
Will have to introduce a blue curing light to the spectroscope in that other thread.
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The first cure gun I made for our initial glue experiments used "Dental blue" LEDs, 465nm. 3x 5W LEDs made by Luxeon. Worked just fine for curing glue, despite the supplier saying it wouldn't work and we'd have to buy their expensive metal-halide cure system.
When you dig deeper you find that the photoinitiators will work with quite a wide wavelength range, but they usually have one or two absorption peaks that give the best cure vs light dose.
The other thing to remember is that the shorter UV is generally better at overcoming oxygen inhibition at the glue surface. Blue light works, but tends to leaves the surface tacky.
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I bet the dental application needs to avoid wavelengths that would injure human skin.
Anybody ever compare the mW-s/cm^2 to cure a few layers of tooth filling putty, with the the UV dose from an hour of tropical beach sunlight?
Maybe blue became a standard decades ago,
before there were LED alternatives to spectrally filtered tungsten-halogen lamp light. The blue radiance must naturally beat the UV radiance, even though UV blocking glass is a popular option in MR halogen lamps.
Another case where LEDs don't always win, cost-wise:
Near-infrared illumination of large areas for surveillance cameras.
Halogen lamps with visible-blocking filters still have places, but might be dwindling.
Anybody know of sports arenas that have announced switch to LED lighting?
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https://www.lighting.philips.co.nz/systems/packaged-offerings/public-spaces/arena-experience (https://www.lighting.philips.co.nz/systems/packaged-offerings/public-spaces/arena-experience)
I would think most existing arenas would be waiting for their existing equipment to become unreliable before changing. But for new builds LED makes sense.
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UV curing with LEDs depends on the adhesive and the chemistry used in the cure. Many adhesives require a broader spectrum than a single bin(LED color) can provide and metal halide lamps are recommended. Metal halides also provide forward IR that helps some of the adhesive to cure as well. Some LED cure systems provide a multiple of different wavelength leds to increase the UV spectrum.