Want to stick pvc

This topic has 9 replies, 7 voices, and was last updated 22 April 2017 at 23:07 by Simon Williams 3.

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21 April 2017 at 16:22 #294374
tiler Jones
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@tilerjones74981
Hi

I have a pvc waste pipe which I have threaded and I want to screw a what looks like injection moulded valve into it.

I want to seal the joint so it can not be removed but the pvc cement adhesive used for welding pipes does not work with the valve plastic.

Anyone advise me as to what I can use please.

Thank you
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21 April 2017 at 16:22 #8671
tiler Jones
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@tilerjones74981
21 April 2017 at 16:36 #294375
David Jupp
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@davidjupp51506
Seems likely that the valve could be PP, or PE – in which case getting any glue to stick will be a challenge. There are 'pre-treatments' available from some of the adhesive companies that claim to work with Polyolefins, though bond strength may still not be fantastic.

If you are feeling brave, you might 'flame treat' the surface of the valve – just a brief waft through a blue gas flame (not enough to melt/burn it). That should help adhesives to stick. Additives in the plastic can bleed out over time and reduce the effectiveness of such 'treatment', so best to do it immediately before gluing.
21 April 2017 at 16:42 #294376
Ady1
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@ady1
A glue gun?

Silicone?
21 April 2017 at 17:38 #294383
tiler Jones
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@tilerjones74981
Ok I will see how I get on, its a bit of a pain as you say.

Glue gun wont adhere, silicone may be an option but I need it stuck. CT 1 might be an option I was thinking but its a bit of a faf. Thought an epoxi might of done it thats why I asked.

The valve is screwing into a pvc stop end from the inside and I need the thread that is then on the outside to fix too. This is why I need it stuck or screwing onto the outside will loosen the thread into the end cap – if you get me

Thanks
21 April 2017 at 18:23 #294391
Ed Duffner
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@edduffner79357
For PVC electrical conduit we used to use a solvent based 'glue' to bond joints. Egaweld was one brand name and another was a no-name solvent made by Marshall Tuflex.

Ed.
21 April 2017 at 18:57 #294395
Brian Oldford
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@brianoldford70365
You original post suggests the valve will be mechanically attached by a thread. If you only want to seal it can you not use PTFE tape?
21 April 2017 at 19:19 #294399
tiler Jones
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@tilerjones74981
Ye I think I have a version of Egaweld and it doesnt like the molded plastic its whats used to weld waste pipe, it melts both surfaces into each other. I wish it would work.

PTFE is fine but its not a sealer, its Teflon and is made to make easy the coupling of brass tapered joints.

I am making a cylinder, inside the cylinder is a valve threaded through one end, attached to the piece that protrudes through the end will go a fitting that feeds the valve. RH thread out through the end, outside fixing is RH thread. Tighten outside too much and it loosens the other (ptfe will aid this). This is my problem I need to make the valve into the end Safe.

All good fun

Thanks guys

Edited By tiler Jones on 21/04/2017 19:21:38
22 April 2017 at 19:28 #294521
Neil Wyatt
Moderator
@neilwyatt
Ha! I got caught out trying to attach what I thought was PVC to genuine PVC. It barely adheres and the glue wouldn't set.

I went and bought some proper PVC section to replace the strap box stuff.

It really depends on what plastic the valve is made out of.

You might be better adding a second layer of PVC to give enough meat to screw the valve into securely.

Neil
22 April 2017 at 23:07 #294542
Simon Williams 3
Participant
@simonwilliams3
Couple of thoughts –

Don't go anywhere near it with silicon(e), it won't stick to hardly nuffink (it's a gap filler) and once you've contaminated it with those little Si molecules nothing but nothing will stick to it., It's a common fallacy that it will seal a pressure joint, but it won't.

Some pipe fittings are injection moulded with ABS. At this time of night I'm struggling to remember if it's PVC glue that won't stick ABS, or the other way round, but I know one glue sticks (solvent welds) both and the other only sticks the one. But this assumes the valve is moulded from such. If you could put up a picture of the valve it might tell us what we're trying to deal with. If the ABS/PVC choice looks like the right line of logic I'll do the research.

Finally, anything Loctite related wrecks PVC or ABS, don't understand the chemistry but it won't seal no way no how, not never.

HTH Simon
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