The PVC Myth

[system 4-50]

http://www.screwfix.com/talk/thread.jspa?t...15&tstart=0

 

[bunker door firmly closed.]

[alan_fincher]

http://www.screwfix.com/talk/thread.jspa?t...15&tstart=0

 

[bunker door firmly closed.]

I've not read it all, but I think the article there is mostly referring to foams sprayed from a can ? Yes ?

 

That is not, I believe, the same as using expanded polystyrene slabs as insulation in narrow boats.

 

I think you will find there are some on here with real bad experiences of them mixing with boat wiring,to the extent of having to do extensive refits to correct the problem.

 

A search of old threads may well reveal such examples.

 

I don't think this is an urban myth at all.

[RLWP]

PRECAUTIONS IN USE

 

Under normal conditions expanded polystyrene (EPS) is chemically stable and biologically inert and whilst the material is non-toxic, it is inflammable and precautions must be taken in storing, working and applying the polystyrene material to ensure protection against ignition, contact with solvent based products and with PVC - e.g. Electrical cable insulation-due to the migration properties plasticisers in PVC.

 

From this http://www.pacspackaging.co.uk/DATASHEETS/...ene%20COSHH.pdf

 

Richard

[system 4-50]

From this http://www.pacspackaging.co.uk/DATASHEETS/...ene%20COSHH.pdf

 

Richard

 

Thank you. I hadn't grasped the distinction between the foams.

 

I still don't understand what is meant by " due to the migration properties plasticisers in PVC". It is not English as she is normally spuck.

[colin stone]

Thank you. I hadn't grasped the distinction between the foams.

 

I still don't understand what is meant by " due to the migration properties plasticisers in PVC". It is not English as she is normally spuck.

 

It is missing the word "of". Left a bit of PVC TWE cable on a polystyrene slab - just burnt its way through. Polyurethane foam is fine.

[Keeping Up]

Our insulation is made of polystyrene sheets.

 

After 10 years the cables had dissolved their way into the polystyrene sheets. As far as I could tell the cable's outer insulation was undamaged (they are all twin flex in PVC sheath). I had some difficulty separating them, then solved the problem by pushing garden-hose over the cables in situ to act as conduit.

 

Top Tip; if using a garden hose as conduit, make sure it isn't full of baby worms which will grow and then spend the next 12 months dropping out of the ceiling on your head.

[Smelly]

Top Tip; if using a garden hose as conduit, make sure it isn't full of baby worms which will grow and then spend the next 12 months dropping out of the ceiling on your head.

 

Than you... The last time you provided that advice i was smiling for days and it's just raised another. Smiles have been few and far apart this week!

[MoominPapa]

The wiring on Melaleuca is PVC and the insulation is polystyrene. The two do touch each other. This was pointed out by the surveyor so we bought with our eyes open.

 

Actually, most of the wiring is under the gunwhale and therefore doesn't contact the insulation, but the runs to individual switches and lights do. I've removed every switch and back-box to replace them and inspected the wiring I can get to. In places it has locally dissolved the insulation, but the PVC wire covering isn't obviously affected.

 

The mechanism behind this is that the plasticiser leaches out of the PVC wire covering and into the expanded polystyrene. This causes the EP to shrink away from the wire, so the affect seems to be self-limiting as long as the wiring and EP are firmly fixed in place. As long as the wire doesn't stay pushed against new EP for a long time, thus totally depleting the plasticsier, then is seems to be OK in practice.

 

MP.

[blackrose]

Thank you. I hadn't grasped the distinction between the foams.

 

I still don't understand what is meant by " due to the migration properties plasticisers in PVC". It is not English as she is normally spuck.

 

Plasticisers are additives used in the polymer industry to make plastics more - plastic! (i.e. more flexible and pliant). These additives are generally the first components of the material which migrate or move out of the plastic as it ages or degrades under certain conditions.

[Keeping Up]

Although the insulation of the wiring appears to be unaffected after it has dissolved away the polystyrene that it is contact with, does the loss of its plasticiser mean that it will have become brittle and therefore could fail?

[Guest]

My mate told me, that somebody had told his brother, that butyl flex (the heat resistant stuff often used to connect immersion heaters and suchlike) does not react with polystyrene sheet. Can anybody confirm this?

Cheers

[blackrose]

Although the insulation of the wiring appears to be unaffected after it has dissolved away the polystyrene that it is contact with, does the loss of its plasticiser mean that it will have become brittle and therefore could fail?

 

I think that's basically it, so then in extreme cases further movement of the cable could cause the PVC insulation to fall off.

[DHutch]

My mate told me, that somebody had told his brother, that butyl flex (the heat resistant stuff often used to connect immersion heaters and suchlike) does not react with polystyrene sheet. Can anybody confirm this?

Cheers

Yes i beleive that it true.

- Certainly, for the reason of its compatabilty with eps emilyanne uses butyl cable for here lights (wired in the cealing way from trucking)

 

 

Daniel

[Guest]

Yes i beleive that it true.

- Certainly, for the reason of its compatabilty with eps emilyanne uses butyl cable for here lights (wired in the cealing way from trucking)

 

 

Daniel

Thanks Dan.

[John Orentas]

I remember when all the rule was first brought in, in fairness to those concerned it was only ever a theoretical problem and it only applied to PVC cables.. I for one have never heard of anyone having any problems.. Just for the hell of it I used all silicone insulated stuff for all the wiring that be in contact with the dreaded expanded Polystyrene.. I still think it is the best insulation for cabin lining.

[MoominPapa]

Although the insulation of the wiring appears to be unaffected after it has dissolved away the polystyrene that it is contact with, does the loss of its plasticiser mean that it will have become brittle and therefore could fail?

Yes, at least in theory. However the wiring and insulation have been installed on Melaleuca for nearly 20 years and the PVC doesn't seem to be in a bad way. As I said, the loss of plasticiser seems to be limited by the EP shrinking away from the cable. Plus, of course the insulation which is most critical is that stopping conductors touching each other and that stopping conductors touching the hull. These areas of PVC will not be losing plasticiser because they are not in contact with polystyrene.

 

I don't lose much sleep over this.

 

MP.

[Keeping Up]

I don't lose much sleep over this.

No, neither do I

[mayalld]

http://www.screwfix.com/talk/thread.jspa?t...15&tstart=0

 

[bunker door firmly closed.]

 

Not sure why this is contentious.

 

Polystyrene - PVC is a problem.

 

PE - PVC isn't

[Lady Muck]

No, neither do I

Marks and Sparks QC did when I developed kids shoes for them, no plasticiser in any of the pvc, they are the only customer I've ever worked for that insisted on that, ever.

[blackrose]

Marks and Sparks QC did when I developed kids shoes for them, no plasticiser in any of the pvc, they are the only customer I've ever worked for that insisted on that, ever.

 

They must have used some sort of placticiser otherwise they'd be so brittle the kids would never be able to wear them? Perhaps they banned phthalates in particular - one of the most common plasticisers in use with PVC that's meant to be responsible for endocrine disruption.

 

No, neither do I

 

Neither do I, but then I have sprayfoam.

[ChrisPy]

Neither do I, but then I have sprayfoam.

Mike, we'll never convert those luddites who cut up slabs of white stuff and force it into gaps, cover the gaps with sticky tape, hide the mess with panelling, and then decide to brazen it out when someone points out their PVC is de-plasticised and pretend not to have sleepless nights. Prob'ly save £200 into the bargain. And pretend that cutting PU overspray with a bread knife is an arduous task.

 

Sprayfoam is so superior to any other form of insulation because by its very nature it gets into all the nooks and crannnies.

 

At least you and I can really sleep soundly at night ......................

[John Orentas]

It's a very odd phenomenon that whenever this topic comes up the discussion divides along the lines of what happens to have been fitted in their particular boat, even if the original decision of what type of cabin insulation was to be used was very far removed from them..

 

A bit like those who support a particular football team for no other reason that they happened to be born within a few miles of the ground..

 

Both types of insulation and many others for all I know are still on open sale for use in houses so presumably there is no reason for any of us "not to sleep soundly in our beds".

[ChrisPy]

.......the original decision of what type of cabin insulation was to be used was very far removed from them..

Eh?

 

PU foam was an option.

I selected it and paid for it.

QED.

[RLWP]

Eh?

 

PU foam was an option.

I selected it and paid for it.

QED.

 

You may have done. We didn't as we bought second-hand.

 

Richard

[Lady Muck]

They must have used some sort of placticiser otherwise they'd be so brittle the kids would never be able to wear them? Perhaps they banned phthalates in particular - one of the most common plasticisers in use with PVC that's meant to be responsible for endocrine disruption.

 

Yes it was the phthalates. I can still remember alltheir quality control standards, even though it's a decade since I last worked with them.