Bonding polycarbonate which will stick underwater

[Beckipedia]

Dear all
First time poster but Eng-tips has been a great resource to me recently.

Is there an adhesive or bonding for two polycarbonate sheets that will stay in seawater?

The sheets are about 12mm thick and need to stay put for up to 3-4 weeks.

I have been told that Cyanocrylate will work on dry land but it is water soluable so wouldn't under water.

Would Methylene chloride work?

Thank you in advance

Becky

 

[Demon3]

Yes, that will work. Silicone caulk should too.

Chris DeArmitt PhD FRSC CChem

 

[MikeHalloran]

Consider 3M #5200 Marine Adhesive/Sealant, a polyurethane product that works well in water. Beware; once cured, it's very difficult to remove.


Mike Halloran
Pembroke Pines, FL, USA

 

[Compositepro]

Cyanoacrylate is not water soluble. It will bond polycarbonate but there also is some possibility of solvent stress cracking because the adhesive itself is a strong solvent until it cures. Poly carbonate is sensitive to solvent stress cracking. Cracking will not occur until sometime after bonding. Do not use solvent based glues.

Silicone will safely make a seal but not a high strength bond.

 

[Compositepro]

Do you mean that you will be doing the bonding under water? That's a special problem.

 

[btrueblood]

CP, that statement from the OP had me curious too, and had to go google to find the info already posted by you when I came back.

OP:

Cyanoacrylate may be too weak for your bond, i.e. if the bond must resist significant shear forces, but water submersion shouldn't rule it out. It's used e.g. in human surgical applications, and in aquariums for bonding coral starts, so it can't be "water soluble", or even weakened much by water immersion.

Mike has a good suggestion, I think he's made it before, because we used that stuff to seal an extension to our 10,000 gallon water tank, it has held up pretty well in spite of some unforseen flexure/vibration of the tank walls.

If your proposed bond needs high strength, maybe consider an epoxy.

 

[patprimmer]

Here is what Bayer say about their Makrolon brand polycarbonate in Document number KU46100e. Edition:8.84.E9i-875/852634.

Makrolon parts can be bonded together with the aid of solvents, such as methylene chloride, which slightly dissolves the contact surfaces before bonding.

Two pack adhesives, such as those based on epoxy resin, silicone (with amine free hardener) or polyurethane can be used to bond Makrolon parts to one another or to other materials. Adhesives based on epoxy resin, silicone or polyurethane can only be used, however if they do not contain components incompatible with Makrolon.

A technical bulletin from Mitsubishi Gas Chemical Company inc. about their Iupion brand polycarbonate and printed about the late 1970s states:-

10. Bonding and Welding

10.1 Solvent bonding (cf. "Iupilon Technical Report-PCR 102")

Iupilon is soluble in chlorinated hydrocarbons and Iupilon pieces can be bonded together by applying a proper solvent or a Iupilon solution. Methylene chloride and ethylene chloride are commonly used as a solvent.

In solvent bonding, a solvent is applied to the surface to be bonded and the greater part of the solvent is allowed to evaporate off before bonding. Or else, the removal of the solvent becomes extremely difficult later.

The pieces are put together, placed immediately thereafter under load of 1-2 kg/cm² for about 4 hours, and dried in air for about two days. The drying can be done efficiently at 60-80°C.
Evaporation of the solvent by application of heat must be carried out only when the amount of the residual solvent becomes very small; otherwise there is danger of the resin dissolving.

10.2 Adhesive Bonding (cf. "Iupilon Technical Report-PCR 105")

In bonding Iupilon together or Iupilon with another material, the best solvent must be selected from a large number of adhesives in consideration of the conditions of use and the combination of materials to be bonded. Common adhesives are those of the rubber type, isocyanate type, and epoxy type.

Factors such as heat resistance, strength, elasticity, and bonding speed must be considered in choosing the adhesive best suited for the purpose.

For example, suppose Iupilon is to be bonded with a piece of metal, a relatively soft adhesive must be selected in the application where heating and cooling are repeated, because there is a difference in the coefficient of thermal expansion between the two. An adhesive of this type gennerally shows poor heat resistance, and a heat resistant adhesive might be sought for in high temperature applications.

The bonded pieces are placed under a load of 3 kg/cm², and enough time is allowed for curing before use.

It is to be noted that some of the adhesives of the solvent type cause cracks in Iupilon under stress.

The above quotes are verbatim to the best of my typing ability and include all grammatical errors included in the original documents.

It can be seen from the above data that PC can be solvent welded with DUE CARE, but it is susceptible to solvent stress cracking and joints should be made to reduce stress to acceptable limits while ever residual solvents are present.

I have often seen methylene chloride used with success. Care should be taken in handling methylene chloride due to OH&S issues with chlorinated hydrocarbons.






Regards
Pat
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[patprimmer]

If you are trying to apply the adhesive underwater that is an entirely different problem.

3M may have a double sided tape that may work, but that is pure speculation on my part. You would need to contact their tech support in your area.

Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers &

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[Beckipedia]

Thank you everyone for replying;

Sorry for the ambiguity Compositepro and btrueblood: the bonding will occur on dry land thankfully , just be submerged at a depth of about 30m for a couple of weeks. It sounds like Cyanocrylate would not be strong enough to support those forces. Buit I shall investigate the other adhesives mentioned.

Kind regards

Becky

 

[btrueblood]

You've got me wondering, though Becky. Please post back if you learn something about this further, or even just to let us know what you did and how it turned out.

 

[patprimmer]

My money is on methylene chloride solvent welded so long as the residual solvent is dried off well enough. It certainly worked well enough on surf board fin boxes which are quite highly stressed at times.

Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers &

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[btrueblood]

No doubts there, Pat. I'm still curious about whether cyanoacrylate adhesives hydrolyze at/near room temp's. in water. A lack of data from googling does not necessarily mean it won't, it may just mean that nobody's done a long enough duration test.

 

[MacGyverS2000]

bt,

Getting slightly out of my element, but... once the solvent has evaporated, isn't the weld just as strong as if the material had been molded to that shape in the first place (assuming proper wetting and pressure of both surfaces)? The CA should temporarily "melt" the two surfaces, allowing them to bond as one structure once the solvent evaporates. Once evaporated, there's nothing to hydrolyze, other than the original base substrate, no?

Dan - Owner

http://www.Hi-TecDesigns.com

 

[btrueblood]

MAc,

CA is not a solvent-weld "glue", it's a polymerizing adhesive glue. The CA resin polymerizes in contact with moisture, and most rapidly when it's a thin film in contact with a surface. CA might melt and weld with an acrylic plastic substrate, but the OP was talking PC.

I think you are right regarding solvent bonding in general, e.g. PVC cement in pipes.

 

[patprimmer]

A solvent weld or bond in theory might be as strong as original material and certainly as strong as a film cast from solution, however in practice you cannot get anywhere near the contact pressure seen by the material in injection moulding, you do not get the crystal structure in a semi crystalline material, and there is always some trapped air and solvent That is why PVC pipes for example use a pipe in socket type joint instead of a butted or even skived joint. Injection moulding depends on pressures on the melt in the range of 10,000 to 20,000psi to compress the molecules together tight enough so they cool with maximum density and maximum intermolecular bond strengths. Remember electrical charge type bond strength is inversely proportional to the square of the distance between the charges.

With solvent bonding of plastics you need a joint design with large surface area contact. Pressure helps a lot and some heat at the appropriate time can help.

Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers &

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[Beckipedia]

Hi all
Thanks for the advise. I ended up using Bostik ExtruFix for the polycarbonate edges and seemed to work fine. The polycarbonate was submerged for a period of about 4 days with some drilling debris hitting it (but apparently not very bitg and not with much force as there were no scratches) and the bonding held fine. There is no evidence that I can see of crazing
All the best
Rebecca

 

[MacGyverS2000]

Thanks for the update...

Dan - Owner

http://www.Hi-TecDesigns.com