Permanent Adhesive LEXAN to ALUMINUM ??

ALU frame
Or
ALU sheet

My experience with ALU is scrub with scotch bright
Rinse with vinegar wash , paint or glue or whatever as soon as dry aka within minutes
Liquid nails usually works for me
I haven't tried it with lexan
The last window and frame I made with ALU and lexan was 20 yrs ago
I drilled holes thru the ALU and lexan and riveted it together and riveted in place
Then sealed frame edges and rivet holes with 3m marine sealant
That window went thru many thunderstorms and never leaked

My first choice would be 3M's VHB structural adhesive tape. Make sure the surfaces are very clean and free of debris, roughing is not required as VHB uses molecular bonding, a smooth surface is better.

If the panels come apart, it won't be at the bond.

They do make a glazing specific formulation - perhaps it offers more UV resistance than the non glazing type?

AL heatsink black anodized
300 watts LED
Expected plastic temp max 110c (BTU radiation)
Fins are spaced .045". Rivets contraindicated
Airtight imperative sea shore environment
Convection cooling (Yrchhh!)
The "air tight" part is what worries me.
The power supply will be remote (30 meters)
Lexan for little boys with big slingshots

110c. That's approx 230f

You need something rated for engine temps
Rivet it seal everything old style permatex gasket compound it will stay air tight

I'd suggest a butyl seal strip (not that RV tape, junk) and mechanical clamps. You're relying on Lexan being impermeable for a long time and that isn't my experience. I'd bet that one of your young nino's will eventually hit the target and you'll be repairing the lense.

For bonding polycarbonate, I've used a plastic solvent cement. It came with an applicator that lets a user apply the cement into the joint and the result is a solvent weld. I suspect the solvent is akin to MEK.

For polycarbonate to aluminum, that VHB tape can't be beat, I'm thinking. Maybe one of the newer polymer sealants would do the trick, too.

I would do a mechanical seal for that application- frame and gasket, screwed together.

110c for LEDs is pushing it, even for latest generation 'industrial' grade Lumileds products (rated to operated at up to 150c but not for very long)... and I know the monster leds on e-bay/etc aren't using these very expensive emitters.

A silica-carbide junction will take these temps all day long, but they are still having trouble with the phosphors breaking down... need more progress in magic quantum dust (dots) to perform the frequency conversion from blue to yellow.

Have you considered active cooling to bring that temp down, or is longevity not a concern?

I have .045" clearance to the next fin. By design rivets expand so I am limited to screws. I imagine the thickness of the heatsink fin to be roughly .020" This imparts a little head-scratching thread-holding wise. Not even a RIVNUT fits. Also musing the design if I overlap the fin, the end caps become a little dicey to seal...eh? 300 watts is going to broadcast a lot of heat radiation. I could make the space taller.

If a kid with a slingshot can fracture .250" Lexan, he would have already been employed by one of the cartels.

GordonThree wrote:
My first choice would be 3M's VHB structural adhesive tape. Make sure the surfaces are very clean and free of debris, roughing is not required as VHB uses molecular bonding, a smooth surface is better.

If the panels come apart, it won't be at the bond.

They do make a glazing specific formulation - perhaps it offers more UV resistance than the non glazing type?

+1 on 3M VHB tape.

Funny thing about LED's...

They'll be bonded to the heatsink with Arctic Silver adhesive. But radiation not convection is the thing that will heat the polycarbonate. It is a very poor thermal conductor so heat direct thermal transfer to the heatsink is not viable.

I have measured in excess of 20c differential between LED base temperature and lens temperature so radiated heat definitely is involved.

My aim is to maintain LED chip base temperature at 50c actual, or less.

Looks like Minnesota Mining Manufacturing VHB wins out here. For mounting to AL as well as bonding poly to poly. (3M is one of my USA -Hero- companies)

Thanks to a lively, informative discussion I better understand my options. Mil Gracias.