# Lexan lid. How well does silicone adhere to lexan (polycarbonate)



## mistergreen (Dec 9, 2006)

Try it out but generally, silicone will eventually peel away from plastics. It's too smooth like teflon.


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## Digs (Jun 15, 2011)

so would roughing the lexan up a bit with sandpaper where the silicone will be help this?


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## mistergreen (Dec 9, 2006)

It could work. Use fine grit and and clean with rubbing alcohol.


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## Digs (Jun 15, 2011)

thanks ill give it a go


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## Bubba Shrimp (May 7, 2012)

sounds like a good project post a finished pic if you can


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## AquaLady86 (Jun 2, 2013)

Whats going on? Update please.


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## lochaber (Jan 23, 2012)

maybe check with some of the online retailers, or a plastics supplier, and get one of those strip hinges. I've also seen regular and piano style hinges made out of acrylic, you may be able to solvent weld something like that on.

Also, check the areas near where they sell acrylic, etc. in the hardware store, sometimes they have sealants/caulks stocked there that will adhere to acrylic (but I've got no idea how suitable they are for a tank).


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## flight50 (Apr 17, 2012)

mistergreen said:


> Try it out but generally, silicone will eventually peel away from plastics. It's too smooth like teflon.


Glass is just as smooth. Glass needs silicone as acrylic need solvents. I doubt if roughing up acrylic would do much. Silicone will stick to acrylic but it won't be a strong bond my any means. One of two things will happen. It will eventually fail or it can be easily pulled apart, which ever happens first.


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## mistergreen (Dec 9, 2006)

flight50 said:


> Glass is just as smooth. Glass needs silicone as acrylic need solvents. I doubt if roughing up acrylic would do much. Silicone will stick to acrylic but it won't be a strong bond my any means. One of two things will happen. It will eventually fail or it can be easily pulled apart, which ever happens first.


you would think glass is smooth. 
This is what it looks like under the microscope. The OP does not want a bonded box to hold water. He/she wants a hinged lid.


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## stealthypotatoes (Feb 2, 2013)

I wouldn't use silicone as a hinge. its probably going to just make a mold out of the lexan
I would find some hinge and just superglue it.
Or like what lochaber said with the acrylic hinges
http://www.usplastic.com/catalog/item.aspx?itemid=24343
Theres a link to it


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## flight50 (Apr 17, 2012)

It doesn't matter whether its a box to hold water or a 2 part lid, silicone won't hold to plastic, it just doesn't adhere well. With the naked eye no one can see or feel the difference between glass vs acrylic but its a cool pic nevertheless.


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## Digs (Jun 15, 2011)

Thanks for he replies everybody. Sorry I haven't posted back on this thread in a while. I went ahead with the build despite my hesitations about the silicon sticking to the lexan. It ended up turning out great! I have been using these lids for 4 months now and the silicone is holding very strong. 

Here is a picture to show the joint I made on the lids. Normally the light sits right behind the hinge and you can't see it at all.. I just moved it back for the picture.









I love these lids they are very low profile and IMO don't detract from the rimless look one bit. Also the lexan dosen't bow like acrylic does which is nice. No more worrying about top offs or jumping fish.








If anyone is interested in building these let me know and I can show you the exact silicon I used. It does say that it is 100% silicon meant for lexan


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## Indychus (Feb 21, 2013)

Yes, please post some details on the materials and process used.


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## Indychus (Feb 21, 2013)

Digs said:


> Also the lexan dosen't bow like acrylic does which is nice.


Lexan has a lower flexural strength than acrylic, meaning it is more susceptible to bowing or bending. I'm guessing yours not bowing is due to the thickness of the lid and not the material.

http://www.hydrosight.com/technology/polycarbonate_vs_acrylic.php

On the upswing, your lid is probably bulletproof and looks fantastic.


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## Digs (Jun 15, 2011)

Indychus said:


> Lexan has a lower flexural strength than acrylic, meaning it is more susceptible to bowing or bending. I'm guessing yours not bowing is due to the thickness of the lid and not the material.
> 
> http://www.hydrosight.com/technology/polycarbonate_vs_acrylic.php
> 
> On the upswing, your lid is probably bulletproof and looks fantastic.


Hmm good point. The Lexan is a good bit thicker than the acrylic I was working with.


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## Digs (Jun 15, 2011)

Unfortunately I do not have pictures of the building process. But basically I just cut the lexan sheet (1/8") to the shape of my aquariums using an acrylic scorer. My tank has curved edges on the front so I took my carving knife and roughly shaped the front corners and then sanded them to get a smooth curve. I cut the lid in half where I wanted to put the hinge, layed the two pieces together, taped them down and squeezed out a thick line of silicon over it. I then took my fingers and ran them over the edges of the silicone to spread it thin on either side of the cut to increase the surface area between the glue and lexan. Let dry for 48hrs and they were good to go. 

To maintian the low profile look I decided against making a handle for the lid. If i'm working in the tank I take two suction cups tied together with fishing line to suction the front of the lid to the back of the lid if that makes sense. Works like a charm and I have plenty of room to access anywhere inside of the tank

Here is the adhesive I used


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## Chronados (Jan 28, 2013)

Silicone will adhere fine with Lexan if you rough up the surface a bit. I did an internship at a company that made a competing polycarbonate product and ended making a 12" cube that held water with regular silicone adhesive (not even the good stuff that professionals use) out of some leftovers.


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