MIgration Of Plasticizers From PVC Cables

[Onoff]

A wordy thread title there!

 

There's been some discussion on another thread reference the possible detrimental effects of "cables" being in direct contact with:

 

- Solid insulation products namely EPS. PU and PIR

- Expanding foams (assuming PU)

- Silicones / mastics

 

I'm really no expert on the science of this but have personally seen T&E (twin and earth) "sunk" into EPS walls and similarly into loose fill and solid EPS between joists. It was pointed out to me as a then mate in a "trickle down / hand me down knowledge" sort of way. My understanding is that the plasticizers used in the cable to give flexibility leech(ed) out over time. This is certainly the case when you see old T&E where the surface is cracked and crazed. It would do that on its own even if clipped direct. Some T&E, years on you can strip by hand! Other factors come into this such as the heating/cooling the cable is subject to under load and thus repeat low level expansion/contraction. Add in exposure to UV from sunlight and there's a few factors to consider.

 

I attempted then to find some scientific basis for all this. There's loads of forums with peoples personal opinions. There's anecdotes on the lines of "I sandwiched a bit of T&E between two shhets of polystyrene for 10 years and it was fine!". We all have stories but I wanted some "facts". I've tried to keep to official sources. I've even avoided the IET as there's so many opinions on ther. There is then this PDF from East Sussex Fire worth it for the pictures alone:

 

http://www.esfrs.org/black-museum/all-the-black-museum-cases/pvc-cable-insulation-and-polystyrene-insulation/

 

Personally I think it could be a bit glossed over saying the fault was not due to thermal effects of covering the cables with EPS. More likely a combination of factors as in the cable runs warmer, more plasticizer leeches out and stays semi-encased, the cable becomes brittle etc. It's not overly scientific and indeed goes on to reference this from General Cable down under:

 

http://www.generalcable.co.nz/getattachment/0ebda90b-b4f8-43ae-b622-c9280295116b/PVC-Cables-in-Contact-with-Polystyrene-or-Bitumen.aspx

 

Note though how the General Cable sheet specifically mentions PU as well. The fact that the plasticizers are absorbed into the cable during the compounding process, one could reasonably assume if the cable then gets overly "hot" the plasticizer could (will?) leech back out.

 

Dig further via the Green Building Forum and there's this:

 

http://tratosgroup.com/quality/cpr/

 

The Tratos page on the new Construction Products Regulation does make mention of the product not releasing dangerous substances during normal operation. This I imagine would cover cables that are "non migratory" in that the leeching effect has been minimized. 

 

A bit from Voltium here confirming EPS is the real one to watch:

 

http://www.voltimum.co.uk/articles/q-day-are-pvc-cables-still-damaged-contact-expanded-polystyrene

 

The Irish ETC:

 

http://www.riai.ie/public/downloads/ECTI_Warning.pdf

 

Jablite:

 

http://jablite.co.uk/wp-content/uploads/2016/01/Jablite-EPS.pdf

 

Loose filling cavities with EPS with generic packing beads I imagine could cause a serious issue, especially if there is old T&E in there which is anyway breaking down through age. A worry for retrofitters.

 

http://www.pacspackaging.co.uk/DATASHEETS/Expanded Polystyrene COSHH.pdf

 

One reason apparently why when you buy say a new pc encased in EPS packing the mains leads are always in their own plastic bags!

 

PU doesn't appear to get off the hook by any means:

 

http://www.prysmiancable.co.nz/insight/pvc-cables-recommended-installation-practices/

 

My view is that all the products, cables, "foams" etc have evolved and are evolving. Certainly T&E nowadays seems harder to strip than years ago but then I might be getting less dexterous!

 

A bit here on foams, Evo-Stik specifically their foam won't damage the pvc coating on cables but go onto to say about the effect of enclosing "long runs". In reality that should be taken as anything more than 500mm.

 

http://www.bostik.co.uk/diy/product/evo-stik/Foam-Filler/68/faq

 

Siicones, Voltium saying probably not but with so many variants etc:

 

http://www.voltimum.co.uk/articles/q-day-will-silicone-sealant-adversely-affect-cable-insulation

 

It comes down then to then selecting products that are fit for purpose as in does it specifically say it is for use around "cables"? And read (keep?) the product data sheets. There is always going to be some reservation on the part on electricians with some justification given the history of the problems and potential outcomes. The old better safer than sorry thing!

[ProDave]

By the sounds of it the only insulation that is really "safe" to be in contact with cable is mineral wool / earthwool type. I have never found a cable in contact with those to have suffered any damage (except overheating due to being encased in too much insulation)

 

How do LSF cables fare with EPS? any difference to ordinary pvc?
 

[Jeremy Harris]

Nice to see this clearly set down.  I've lost count of the number of completely false tales I've heard about such and such a material attacks cables, when it doesn't at all.  There seems to be a lot of confusion around about this, even in the trade.

 

EPS is the real problem material, as the above highlights, as it can leach the plasticiser from some forms of PVC, but over the years most common sealants and expanding foams seem to have been made "cable safe" and usually say so. 

 

The issue of cables in insulation is now pretty significant in many new builds, I suspect.  Building regs require acoustic insulation in ceilings and stud walls, and often dense rockwool is used.  This is a pretty good thermal insulator, too.  In our build around 80% or more of the cable runs were in the ceiling or stud walls, and so are effectively enclosed in insulation for much of their length, and needed to be de-rated in accordance with Appendix 4 of the regs, bearing in mind that there's no Installation Method for cables run in rockwool (at least none of the tables in my copy of BS7671 detail it - not sure if it's now in Amendment 3 or not), so some judgement needs to be applied.  The closest is Installation Method 101/102 in table 4A2, but that assumes a cable in contact with the inside of a wall surface, and that may not be the case in a well-insulated build.

Edited February 14, 2017 by JSHarris
typo

[Jeremy Harris]

4 minutes ago, ProDave said:

By the sounds of it the only insulation that is really "safe" to be in contact with cable is mineral wool / earthwool type. I have never found a cable in contact with those to have suffered any damage (except overheating due to being encased in too much insulation)

 

How do LSF cables fare with EPS? any difference to ordinary pvc?
 

 

PIR is OK generally, as it's usually covered with foil, and PU insulation isn't at all common, in my limited experience.  Sheet insulation seems to be either polystyrene-based (EPS or XPS) or isocyanate based, like PIR.  Although PUR is available, it has always been expensive whenever I've looked around.

 

LSF is just a low smoke and fume formulation of PVC, AFAIK, so to be safe it should be treated as if it were PVC and not used in contact with EPS or one of the very few sealants or expanding foams that attack PVC.  LSHF is a different formulation and is not based on modified PVC, so should be OK, but I've seen no test evidence to support that view, it's solely from looking at the chemistry of the stuff.  As such I'd treat LSHF as being susceptible to plasticiser leaching if in contact with EPS until proved otherwise.

 

[Onoff]

LSF I'm sure fares better, specifically on the leeching, but I can't remember where I read that. Will dig out the "official" source on that later.

 

PU I don't think is out of the woods if the conditions are such as to accelerate leeching and breakdown of the cable such as increased temperatures. Hence adhering to the whole halving the cable current carrying capabilities business if run through more than 500mm etc. 

 

Again, retrofitting leaving old "leechy" T&E in place and so on. Take those comments with a large dose of "IMHO" btw.

 

Maybe another project that'll never happen, encase a length of T&E in PIR and overload it, then do some in "foam",  clamp meter on etc. "We washed this half in....!"

 

 

 

[Jeremy Harris]

10 minutes ago, Onoff said:

LSF I'm sure fares better, specifically on the leeching, but I can't remember where I read that. Will dig out the "official" source on that later.

 

PU I don't think is out of the woods if the conditions are such as to accelerate leeching and breakdown of the cable such as increased temperatures. Hence adhering to the whole halving the cable current carrying capabilities business if run through more than 500mm etc. 

 

Again, retrofitting leaving old "leechy" T&E in place and so on. Take those comments with a large dose of "IMHO" btw.

 

Maybe another project that'll never happen, encase a length of T&E in PIR and overload it, then do some in "foam",  clamp meter on etc. "We washed this half in....!"

 

 

 

 

 

If you have a source it's be useful.  Looking at the chemistry, LSF seems to be very similar to unmodified  PVC in terms of the way the plasticiser is bound with the polymer.  LSF is PVC based, whereas LSHF isn't PVC based.

 

Someone needs to do some more testing to get another Installation Method in table 4A2, now that many new builds will have cables running pretty much embedded in rockwool, rather than in contact with a surface.  In my ceilings the cables are clipped to the posijoists, but have 150mm of rockwool in close contact with them all around, and I suspect that sort of installation is now pretty common in new builds.

Edited February 14, 2017 by JSHarris

[SteamyTea]

I heard a story back in the 1980's when I was doing some tooling for Ford (the rear screen surround of the P100 pickup) that the plasticiser used in the dashboards was leaching out.  This caused that sticky film on the windscreens.

The guy telling me about it was a bit of a worrier and then said 'it is carcinogenic you know'.  Not sure if that was true.

[Jeremy Harris]

1 minute ago, SteamyTea said:

I heard a story back in the 1980's when I was doing some tooling for Ford (the rear screen surround of the P100 pickup) that the plasticiser used in the dashboards was leaching out.  This caused that sticky film on the windscreens.

The guy telling me about it was a bit of a worrier and then said 'it is carcinogenic you know'.  Not sure if that was true.

 

The story is pretty accurate.  The nasty film that built up inside windscreens was condensed out plasticiser, the question would be whether it was sufficiently carcinogenic to cause a health risk.  Pretty much everything around us is toxic to some degree, it depends where you want to start worrying about it!  The LD50 of dihydrogen monoxide (roughly the dose that will kill 50% of those who ingest it) is around 90ml/kg body weight, so for me at 80kg that's a dose of around 7.2 litres.

[SteamyTea]

Isn't the LD50 and the long term exposure to a carcinogen measured differently though.  I can't remember, fell asleep when I had to sit though a couple of presentation on it.

[Jeremy Harris]

8 minutes ago, SteamyTea said:

Isn't the LD50 and the long term exposure to a carcinogen measured differently though.  I can't remember, fell asleep when I had to sit though a couple of presentation on it.

 

It is, yes.  The LD50 is a measure of acute response, not long-term, low level exposure. 

 

The question in the case of the car dash stuff is really about what the exposure level would be and how long someone would be exposed to it.  Cars are pretty well ventilated, especially in hot weather when the problem arises.  I'm pretty sure it's also a problem that's gone away now, too.  The last car where I can recall getting that nasty film build up on the inside of the windscreen was a mid-80's Peugeot 205.  I can't say I've seen it at all for many years now.  Mind you, the dash in the Prius is made from a vegetable based plastic, and it's lack of toxicity was one of the original selling points pack when the car first came out.

Edited February 14, 2017 by JSHarris

[Onoff]

Leeching. Skimmed it and saw a bit about cables made in the 70's. WAAAAYYY too heavy for me!

 

http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.627.6558&rep=rep1&type=pdf

[Onoff]

51 minutes ago, SteamyTea said:

I heard a story back in the 1980's when I was doing some tooling for Ford (the rear screen surround of the P100 pickup) that the plasticiser used in the dashboards was leaching out.  This caused that sticky film on the windscreens.

The guy telling me about it was a bit of a worrier and then said 'it is carcinogenic you know'.  Not sure if that was true.

 

Cars - that helped me find the link. It was Volvo commissioned this. I remember getting as far as reading the names of the two birds who wrote it then having ABBA esque fantasies, there was that evening where they put the report to one side etc  Anyway, stuff in there about pu "foams" Says about warranting further investigation. I've written and offered my services!

 

http://bada.hb.se/bitstream/2320/9301/1/2011.2.10.pdf

[Jeremy Harris]

That paper was really looking at the way plasticisers migrate from PVC over long time periods in air, specifically in the context of long-term reliability for use in nuclear plants, where access may not be possible for 50 years.  It supports the evidence from elsewhere that plasticisers so evaporate out over time, particularly at elevated temperatures.  This is the car dash problem, where the windscreen gets a coat of plasticiser and the dash plastic ends up brittle.

 

With PVC cables the effect happens at normal temperatures when they are touching polystyrene, especially EPS, but chemically XPS is practically the same, so I'd expect it to have the same effect.  It doesn't take long for this to happen, either.  When we bought our old house the previous owner had done a lot of DIY (renovating it to sell I'm sure, as everything looked new).  One thing he'd done was lay some chipboard flooring in the loft, for storage space.  When we had cable run in, I had to lift some of that flooring to get a cable feed to my study, where the cable modem was going to be.  What I found was that there was EPS laid under the chipboard flooring and wherever it had been touching a cable it had a brown streak across it, not from heat, but from the plasticiser in the cables.  At best that insulation had been down for two years, probably less, so it doesn't take long for adverse effects to appear.

Edited February 14, 2017 by JSHarris

[Jeremy Harris]

26 minutes ago, Onoff said:

 

Cars - that helped me find the link. It was Volvo commissioned this. I remember getting as far as reading the names of the two birds who wrote it then having ABBA esque fantasies, there was that evening where they put the report to one side etc  Anyway, stuff in there about pu "foams" Says about warranting further investigation. I've written and offered my services!

 

http://bada.hb.se/bitstream/2320/9301/1/2011.2.10.pdf

 

That's a good description of what happens with PVC plasticisers, pretty clearly explained, too.  It also highlights the health concerns with pthalate plasticisers, something I think was first raised around 30 or so years ago in the context of PVC food and water containers and most probably the reason ST's mate was concerned about the stuff evaporating out of his dash.