type of plastic use in UK home electrical fittings

[mikey]

What is the name of the brittle plastic used in UK electrical
fittings for mains wall sockets and that sort of thing?

I mean the plastic that a bit like the old bakelite.

 

[newshound]

Casein - made from milk solids.

Colin Bignell

That surprised me. My copy of Brydson's Plastic Materials (1975) says

"when dry, casein is a good electrical insulator but is seriously affected
by humid conditions. For this reason it can no longer compete with the many
alternative plastics materials now available for electrical applications"

and

"the once considerable application in knitting pins, pens and pencils is no
longer of importance although a few propelling pencils were still being
produced with casein barrels in 1964".

That said, I don't know the answer, but I assume from the relative
brittleness that high levels of filler are used.

 

[The Natural Philosopher]

I doubt that. I'm not sure that casein resins are stilll made on any
significant scale - the British manufacturers "Erinoid" stopped a long time
ago.

AFAIK, the dark brown stuff on the insides of electrical fittings is mostly
still "bakelite" or at least the modern version of phenol formaldehyde
resin. The white parts on the faceplates etc are most likely melamine
formaldehyde resin. Both parts full of fillers.

Ive been worrying about casein too, bit couldnt think what the plastic
might be: melamine strikes a huge chords tho. I think that's the one.
The cheap thermoset plastic..But I doubt bakelite is used any more at all.

But I take your point that phenolic resin plastics are still around -
typically for cheap PCB and the like.

 

[The Natural Philosopher]

Thought the ABS group were at least slightly flexible? The most common
stuff used on sockets isn't. ;-)

ABS is a thermo plastic. Not used where it gets hot.

 

[Grimly Curmudgeon]

We were somewhere around Barstow, on the edge of the desert, when the
drugs began to take hold. I remember "nightjar" <cpb@<insert my surname
here>.me.uk> saying something like:

Casein - made from milk solids.

Blimey, that'd be handy if you were locked in a room with no food.

 

[Steve Walker]

MK were certainly using them until quite recently. However, checking their
web site, which I obviously should have done before posting, they now say
they use 'moulded urea', presumably meaning urea formaldehyde

Colin Bignell

Volex were certainly using Urea Fomaldehyde when I drew up the exploded
diagrams and parts and materials lists for the 9000 range 20 years ago.

SteveW

 

[Steve Firth]

Casein - made from milk solids.

Errm, no.

 

[Steve Firth]

I think the main component is ABS (Acrylonitrile butadiene styrene),

No.

The plastic component is usually a thermosetting resin, and as cheap as
possible such as phenol-formaldehyde or phenol-melamine there will also
be some sort of filler. Originally this was wood flour but modern
plastics may use glass as either a fibre or microballoons.

 

[mikey]

Some lines, MK has one, use polycarbonate.

It's interesting to see you mention alternative plastics.

I asked the original question because the way the plastic broke
when I snapped out some holes for the cable was damn crude and
hard to control. I couldn't believe such hard to work plastic
was ever used in a product!

I was using some 16mm surface-mounted patresses to hold
telephone socket faceplates in a very visible location. They had
to look right.

I swore next time I wouldn't use some bargain 50p patress
because it was taking for ever and ever to get them right. Even
them the irregular jagged holes left by the snap-outs were ugly.

If had to pay several times the bargain price it would be good
value for time saved! The result would be better too.

 

[mikey]

You want something surface mounted to look 'right'? ;-)



Strangely most telephone outlets are made of a more flexible
plastic which won't snap in the same way. And goes off white
quite quickly.

You might be thinking of the 55mm x 55mm (LJU1) or 67mm x 67mm
(LJU2) phone socket.

I was installing a couple of the larger 85mm x 85mm phone sockets
(LJU4).

http://www.kitz.co.uk/adsl/btsockets.htm

 

[Andrew Gabriel]

Strangely most telephone outlets are made of a more flexible plastic which
won't snap in the same way. And goes off white quite quickly.

Mains stuff really needs thermosetting plastics so it doesn't turn
into cheese if something goes wrong and gets hot. Telecoms can use
thermosoftening plastics, as there's not enough power there to
overheat anything.

 

[PeterC]

It's interesting to see you mention alternative plastics.

I asked the original question because the way the plastic broke
when I snapped out some holes for the cable was damn crude and
hard to control. I couldn't believe such hard to work plastic
was ever used in a product!

I was using some 16mm surface-mounted patresses to hold
telephone socket faceplates in a very visible location. They had
to look right.

I swore next time I wouldn't use some bargain 50p patress
because it was taking for ever and ever to get them right. Even
them the irregular jagged holes left by the snap-outs were ugly.

If had to pay several times the bargain price it would be good
value for time saved! The result would be better too.

Yes, I found out the 'hard' (brittle?) way that, to some extent, the
patress needs to be of better quality than the fitting. Even a slightly
uneven wall can break a patress before the screws are done up.
As for a cheap patress under a 40A pull-switch...!

 

[Newshound]

I swore next time I wouldn't use some bargain 50p patress
because it was taking for ever and ever to get them right. Even
them the irregular jagged holes left by the snap-outs were ugly.

If had to pay several times the bargain price it would be good
value for time saved! The result would be better too.

I usually dremel the snap-lines before the final snap for just this reason

 

[Mike]

I usually dremel the snap-lines before the final snap for just this reason

I bash it out with a screwdriver and then use a dremel abrasive band
to clean up the edges if the break isn't clean.


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