What sealent for polypropylene?


#1

Can you recommend a sealent that sticks to polypropylene? Silicone lifts right off. Sikaflex 221 apparently is also not suitable.

Today I attached a polycarbonat window. The silicone might seal, but only because its under compression by screws.

I got hot glue to work by roughing up the texture with a chissel. This is only a mechanical interlock. Its not waterproof.


#2

LOL! I was wondering what if anything sticks to PETG. Most epoxy sticks to PLA and NYLON.
I have this I found awhile ago looking for the best nylon epoxy adhesive:

http://na.henkel-adhesives.com/industrial/application-technologies-3533.htm

There is also a Sherwin Williams adhesive site somewhere…

I settled on the Stratasys recommended one in the end, but I doubt it works on PETG or PolyPropylene.


#3

We’ve got that one in France

Primary layer + Cyano + micropowder
https://www.lacollepro.fr/colles-cyanoacrylate/colle-pe-pehd-pp.html


#4

PP and PETG are plastics that are not glueable. It should be very hard to find something.


#5

The reason Sikaflex is not recommended is because its designed as a bonding sealant. But for the purpose of only sealing, I think it works great. You could also rough the surface to maximise the mechanical bonding If you are worried about it.

The only places I don’t use it are where I think I will have to disassemble in the future. Sometimes it works a bit too well.


#6

Sika 291i just to name it has a well deserved reputation in marine industry. Having stacks of that, I used it extensively on my board but on PMMA or perspex, plexiglass and PP it failed. Chemically attack the surface and make it soft. Now I tried a different sealant/glue, silicone free, not famous brand but good for pmma also. Let see. I glued PLA halves of my remote with that, before to lay epoxy on top… It should work.


#7

Yea, Sikaflex recommend 295UV for PMMA and PC. Also some plastics require primers to work properly and who can be bothered with that. I suspect release agent chemicals added to the batch are part of the problem.
Last month I was in a rush and picked up a tube of Sikaflex 552AT by mistake.
It is an automotive sealant and I have had good results with this also. It is solvent and silicone free.


#8

I sticked to regular silicone and hope on the compressive forces to maintain the seal.


#9

Very likely it will stay. Problems arisevwhen you step on it, if one of the parts bend a little. In my case it was the ammeter window on the battery case hatch, I run with my feet on that door…


#10

Just the display. Its tiny.