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Old 18th May 2019, 8:43 pm   #1
PJL
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Default Cable that 'melts' paint in storage

I left a speaker cable made from modern two way double insulated mains cable wrapped up against the paintwork of an amplifier chassis. The chassis had been resprayed with a metallic car paint maybe 15 years ago and was put in storage maybe 5-6 years ago. The cable now has a white residue on the outside and wherever it was touching it has eroded the paintwork exposing the primer so I assume it is a chemical reaction.

I guess the lesson learned is to not trust plastics and always apply a lacquer finish to metallic paints.
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Old 18th May 2019, 9:21 pm   #2
M0FYA Andy
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Default Re: Cable that 'melts' paint in storage

It's all these tales of plastics deteriorating and reacting with other things and other plastics which always come to mind when folk claim that 'plastic film capacitors will last for ever'. We just don't know!

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Old 18th May 2019, 9:33 pm   #3
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Default Re: Cable that 'melts' paint in storage

Such happenings are not uncommon. I left a yellow insulated handle screw driver in a plastic tool box and the handle melted just as if it had been put on a hotplate.
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Old 18th May 2019, 9:41 pm   #4
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Default Re: Cable that 'melts' paint in storage

Was it in a sealed container? PVC outgasses corrosive chlorine compounds which can build up in enclosed spaces, but does not normally cause problems when air can circulate freely. That is the reason for the use of PTFE insulated wire in hermetically-sealed avionics stuff. Using a piece of PVC insulated wire in a sealed assembly can result in dissolved polystyrene capacitors.
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Old 18th May 2019, 9:59 pm   #5
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Default Re: Cable that 'melts' paint in storage

Contact can allow the diffusion of plasticisers from PVC.

David
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Old 18th May 2019, 10:14 pm   #6
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Default Re: Cable that 'melts' paint in storage

When I worked in the TV repair trade it was common to find VCRs on which the mains lead had made an impression in the machine's plastic top while in storage. PVC leads will melt into polystyrene as well. This is why mains leads on new equipment are taped up in plastic bags when in the manufacturers' packaging.
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Old 18th May 2019, 10:24 pm   #7
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Default Re: Cable that 'melts' paint in storage

The plasticisers in PVC can 'migrate' over time and cause unforseen issues: I remember having to do some significant ceiling-level rewiring in a previous house where the PVC-covered cable to the light in the kitchen had developed a deep and meaningful slimy association with some polystyrene ceiling-tiles.

This effect has also been noted with PVC-sheathed cables and some versions of loft-insulating 'wool' spun from recycled plastic drinks-bottles.
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Old 18th May 2019, 10:50 pm   #8
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Default Re: Cable that 'melts' paint in storage

Quite so; the PVC and polystyrene problem is potentially very dangerous. There are inter-reactions between PVC and ABS also. A PVC cable routed around an ABS moulding can leave quite a deep 'melted' mark into it.

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Old 18th May 2019, 11:01 pm   #9
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Default Re: Cable that 'melts' paint in storage

A few years ago I had to claim for some defective audio headset leads from the manufacturers. These were a kind of soft rubber coating which had disintegrated and fallen off the core wires after only a year´s storage. I have since seen this happen on a Nokia phone charger lead.I suspect the material would have decomposed anyway, but I think they were stored in or near some plastic boxes.

I also once changed the captive speaker wire on a small Philips portable record player after the original had gone hard and brittle. A couple of months later, I found the new cable had melted its way into the plastic deckplate of the player!
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Old 19th May 2019, 12:19 pm   #10
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Default Re: Cable that 'melts' paint in storage

I can remember this happening a few times when placing a coiled up mains lead on top of the perspex lid of unit audio systems that had been repaired but had sat on the completed job shelf for several weeks awaiting collection by the owner. The lead wasn't damaged but the lid had melted marks.

Alan.
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Old 19th May 2019, 12:45 pm   #11
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Default Re: Cable that 'melts' paint in storage

There is a bad problem with rubbery leads on Apple chargers. The jacket goes soft and falls apart exposing bare conductors. Not nice and £80 a pop for a new charger. This Macbook is on its THIRD charger because of this.

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Old 19th May 2019, 2:54 pm   #12
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Default Re: Cable that 'melts' paint in storage

The synthetic rubber feet fitted to some equipment melt their way through the polyurethane varnish on my shelves.

Also I have a lot of transparent plastic drawers for components, and have found that "rubber" grommets weld themeselves into the plastic. I presume the drawers are polystyrene. The grommets are OK if packed in polythene bags.
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Old 19th May 2019, 3:24 pm   #13
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Default Re: Cable that 'melts' paint in storage

My otherwise immaculate Bush SRP41 record player suffered in storage a few years ago simply because the PVC mains cable was carelessly draped across the speaker grille. As the photo shows, it etched its way into the 'silver' painted plastic grille in a way that's impossible to rectify - unless someone here knows different!

Martin
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Old 19th May 2019, 10:08 pm   #14
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Default Re: Cable that 'melts' paint in storage

Quote:
Originally Posted by M0FYA Andy View Post
It's all these tales of plastics deteriorating and reacting with other things and other plastics which always come to mind when folk claim that 'plastic film capacitors will last for ever'. We just don't know.
Depends on the plastic. PVC is not good... For cables etc it has a plasticiser added, as others have said, otherwise it would be rigid (like uPVC window frames). But the plasticiser leaches out and attacks things.

Polythene, polyester, PTFE, polypropylene on the other hand don't need anything to enhance their (different) properties. And they'll likely last for a very long time.

Plastics are like metals in that there are loads of different types. Make an article out of iron and it won't survive long in the environment. Make it out of gold and it won't decay at all.

Quote:
Originally Posted by m0cemdave View Post
The synthetic rubber feet fitted to some equipment melt their way through the polyurethane varnish on my shelves.
Probably not synthetic rubber, but PVC, again!

Last edited by kalee20; 19th May 2019 at 10:09 pm. Reason: Punctuation
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Old 19th May 2019, 10:54 pm   #15
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Default Re: Cable that 'melts' paint in storage

I have seen many Fidelity hf45 record players where the mains lead has 'burned' a mark into the plastic turntable
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Old 20th May 2019, 1:27 pm   #16
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Default Re: Cable that 'melts' paint in storage

Those synthetic feet are made from the same material as the infamous Philips belts that turn to goo. I don't think it's PVC.
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Old 23rd May 2019, 5:34 pm   #17
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Default Re: Cable that 'melts' paint in storage

In my time involved with TV assy for NEI...we had to ensure the mains lead was in a polythene bag so as not to come into contact with the Polystyrene packaging.... if stored for a while without a bag the mains lead outer coating would melt the styrene.
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Old 23rd May 2019, 6:07 pm   #18
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Default Re: Cable that 'melts' paint in storage

Quote:
Originally Posted by Wendymott View Post
In my time involved with TV assy for NEI...we had to ensure the mains lead was in a polythene bag so as not to come into contact with the Polystyrene packaging.... if stored for a while without a bag the mains lead outer coating would melt the styrene.
Not styrene, but polystyrene - different things. To quote Wikipedia:

"This derivative of benzene is a colorless oily liquid that evaporates easily and has a sweet smell, although high concentrations have a less pleasant odor. Styrene is the precursor to polystyrene and several copolymers."

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Old 23rd May 2019, 8:30 pm   #19
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Default Re: Cable that 'melts' paint in storage

This has been known for quite a while now, either the set is in a bag, or the lead is, usually both. It's only a problem later in life, when the packaging has long been discarded.
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Old 23rd May 2019, 9:52 pm   #20
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Default Re: Cable that 'melts' paint in storage

A similar problem has occurred with transparent sleeves used to protect vinyl records. I have had a few which 'frosted' the surface of the record, adding terrible background hiss. Fortunately nothing rare was affected, but the worst cases were the single record directly inside a PVC sleeve.
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