Adhesive Recommendation; Metal to Mylar?

There have been quite a number of threads on polishing on this NG - Google is your friend - but, if you want it to STAY shiny, use Stainless Steel instead 'cause Al will, despite the best of efforts, oxidize to a cloudy surface. [Think of the state of a conventional aquarium light hood.] This process begins the instant that the bare metal is exposed.

Once cut to size and all necessary holes drilled, the (still flat) SS can be polished fairly easily. (I use a white - 1500 grit - polishing rouge with a "polishing bonnet" and a 1/4" drill for large objects and with a cotton buffing wheel on a Dremel for small/intricately-detailed items.)

Another advantage to SS: a conventional SS cookware cleaning product works well to remove any surface deposits and "renew" the shine.

Reflective window film kit. Metallized self-adhesive sign vinyl.

3M 77 spray adhesive if you're determined to use other metallized Mylar material.

Jeff, if the "mirrored mylar" you're talking about is the 1/2-mil aluminized "survival blanket" sort of material, then most any Pressure Sensitive Adhesive will work. I'd recommend double-sided carpet tape.

Mylar doesn't take Cloro/fluorocarbon solvents well. It will disintegrate into powder within moments of being contacted by trichlorethylene. Both polyesters and polycarbonates act that way with C/Fcs.

So you're limited to what sort of liquid glues you can use. IIRC, most spray contact cements are hexane solvated, and IIRC, mylar will tolerate that. It handles acetone ok, too.

The thin aluminized mylar is so flexible and so lightweight, it doesn't take much to hold it to a surface. I used the stuff to line "sun tunnels" in my new addition. A small handful of thumbtacks was all it took for a permanent installation.

LLoyd

Since you mentioned it, does anyone know a good source for that "survival blanket" material? I want it on a roll, without the creases. I don't want to buy enough to cover the county; a few hundred feet would suffice, about 3 feet wide. The semi-transparency of the 1/2 mil is desireable for my purpose.

Joe

Flexcon .com sells many colors and guages of metalllic foils for the printing trade. the adhesives are alread on there and are really strong. you can probably just go to any local signmaker and buy a few sheets.

Why does it have to be a specular (mirror) reflector? Glossy white paint has very low reflectance loss and would be easy to apply to the reflectors as well as corrosion proof. Virtually all fluorescent light fixtures use a white reflector.

Randy

Absolutely: there's high-polish mirror finish on vinyl available by the yard in the signmaker shop down the street. It's very attractive, too... pity no one will ever see it.

After you look at the price, you might want to reconsider white paint, though.

One might also consider the silver metallic Monocote model airplane material. It's a heat-shrink polyester film with a hot-melt adhesive pre-applied to the business side.

My 3-meter sailplane had (sigh...) reflective silver wings until the - um - accident.

LLoyd

LLoyd

About $25 per 6 foot roll of Monocote or Econocote model airplane covering material. Iron on adhesive included. Comes in Chrome finish.

Maybe better buys out there, but it's available.

Cheers Trevor Jones

Thank you, Richard. I looked at the 3M 77 at the hardware store today and it looks like it is probably the best choice I've heard of so far. It does not say anywhere on the can whether it is water proof though. Hmmm, maybe 3Ms web stie will have additional information.

I have not looked at the window film kit yet, but it sounds like it might be pricey per square foot and possible difficult to obtain in 4' widths or lengths?

On Thu, 19 Oct 2006 23:03:16 -0500, with neither quill nor qualm, snipped-for-privacy@io.com (Jeff Walther) quickly quoth:

It is waterproof. I use it on my NoteSHADES(tm) glare guards and they're washable. #77 is the very best adhesive I've tried, and I've tried nearly all of them.

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Thank you Lloyd. The stuff I have, I bought here: It is 2 mils thick. I could have bought 1 mil, but thought the thicker material would be easier to work with.

How thick is double-sided carpet tape? I want the mylar to map the shape of the underlying sheet metal as perfectly as possible. An adhesive would be best, but a very thin two side tape might work. The only issue there (other than thickness) is that the sheet metal will have quite a few bends in it, so it might take a lot of tape to get the mylar to follow all those bends.

Can you recommend or name some pressure sensitive adhesives? Would the

3M 77 spray adhesive fit in that category.

Thank you for that tip. I had not even thought about what kind of solvents might dissolve mylar. Okay, so I went to look at 3M's site, but they have even less information on their website than is on the can at the store. Sigh. Accessing datasheets requires an authorization code. I guess it's back to the hardware store to see what's in 3M's spray adhesives.

Okay, so I went to look at 3M's site, but they have even less information on their website than is on the can at the store. Sigh. Accessing datasheets requires an authorization code. I guess it's back to the hardware store to see what's in 3M's spray adhesives.

However, I did find that Spray 77 only tolerates heat to 110F, so I think that what I want is 3M Hi-Strength Spray Adhesive 90. It goes up to 160 F. A light reflector is likely to get hot. Something I did not think about in my initial requirements. Still, I'll need to check the contents, so that it does not dissolve my mylar.

That's a good point. Adhesive strength is really not an issue. The mylar is light. I just need something heat and moisture tolerant that will help the mylar conform to the sheet metal shape.

Oh, gosh. My memory is hazy. This branch in the decision making was some months ago. I tend to conceive of a project and then slowly research it until I'm finally in a position to execute and the desicion points get forgotten.

IIRC, what I read is that white colored surfaces do tend to reflect almost as well as specular surfaces; close enough so that the difference is insignificant.

But there were two problems.

The first may be wildly inaccurate, but this is what I read:

A white surface reflects incoming light in a diffuse manner (please forgive my lack of proper descriptive terms) meaning that incoming light doesn't leave at a reciprocal angle. It tends to go off in various directions. So, if you're building a reflector which is designed to reflect light off of the light bulb and around it to a particular destination, a white reflector will not work as well as a mirrored surface will.

The second reason makes more sense to me:

White paints tend to turn brown after a while spent reflecting light.

I'm not sure this meets your needs because it is 1 mil thick, but here is where I got mine:

However, I bought the 2 mil variety as I hope it will be easier to work with when adhereing it to a metal surface.

Yeah, a few folks have suggested that route, but my impression is that the stuff is quite pricey.

I'm thinking a roll of 10" X 50' sheet metal intended for home roof flashing ($7), a 50" X 25' roll of 2 mil mirrored mylar (~$30 with shipping), and a couple of $10 cans of spray adhesive (I'm starting to lean toward 3M Hi-Strength Spray Adhesive 90), plus advice I get in the news groups (priceless).

Now the next trick will be how to cut the metal cleanly without a shear. Ah, the joy of trying to do projects without proper tools. But the cost of a shear and brake would make it cheaper to just go and buy reflectors.

I've seen the low cost combinations and such. But the reflectors I'm making will range from 24" long (20 gallon aquariums) to 48" long (90 gallon and 200 gallon). A shear and brake that will do 48" lengths tends to be pretty expensive. I would like to make about 12 reflectors. And each reflector will need 13 lengthwise bends in order to approximate with straight lines a parabolic shape. I think I can manage the bending with a couple of 4' lengths of angle metal clamped along the bend. But cleanly cutting sheet without a shear is still a puzzler to me.

This idea is interesting, because whichever route I use I must shape the metal. Using stainless steel would skip the adhering mylar to metal step.

Sooo, I did a little looking around on Ebay and there are folks selling 24 guage polished stainless steel sheet for fairly affordable prices (e.g.

48" X 86.5" for about $100 shipped). It would be more expensive than the road I'm on, but not a lot and simpler and possibly more durable. And I might be able to pay the seller to shear it to the sizes I actually need.

A 3" wide reflector for a pair of 48" long T5 flourescent bulbs needs a 5" X 48" piece of metal. So I can get 17 of those out of a 48" X 86.5" sheet. At the most I only need 13, I think. Maybe 14.

One comment I saw made me curious. The comment seemed to imply that stainless would corrode at shearing. That doesn't really make any sense to me, but is there any truth to it? It's stainless steel all the way through, right? Not just some surface coating, so if you shear it, the edges have no more reason to corrode than the rest of surface?

Larry, Have you compared the 77 to the 99 ? I think I was told (?) 99 was even stronger or somehow better. ...lew...

On Thu, 19 Oct 2006 23:51:55 -0500, with neither quill nor qualm, snipped-for-privacy@io.com (Jeff Walther) quickly quoth:

Make sure it sprays as finely as 77. I tried other brands and they gummed up and lumped on the surface. My cloth covering is a shiny ripstop nylon and the uneven glue showed through. Mylar would do the same thing (but about 50 times worse) due to its mirror finish. Caveat Sprayor.

the $40 shear. It'll be handy in the shop. Clamp a straightedge to both sides of the sheeting before cutting for a good edge and clearancde for the shear head. (Disclaimer: I haven't used one of these shears. They could be excellent, good, or shitty. Suggest you take some sheeting to the HF store and ask to try one out so you can see what edge it leaves.)

So you're making segmented parabolic curved mirrors for aquariums?

See above.

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Given a non-infinite lifetime for mylar, what folks using it for solar heating applications typically do is apply it with axle grease as the "adhesive". When it dies, as it will (and with typical aquarium light sources you'd bother to make custom reflectors for, you probably have the same issues due to UV components in the lighting) it's simple to strip and re-apply.