type of plastic use in UK home electrical fittings

Casein - made from milk solids.

Colin Bignell

"nightjar.me.uk>"

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.

"nightjar .me.uk>"

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.

I think the main component is ABS (Acrylonitrile butadiene styrene), however i would imagine that the actual material is a compound using a variety of additives such a titanium dioxide (white), impact modifiers and stabilizers etc.

I hope this helps.

Tom

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.

Casein resins are still around - mostly for paint binders though.

Some lines, MK has one, use polycarbonate.

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

We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember "nightjar" saying something like:

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

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

Its still not edible. Cheap frozen pizzas use Casein based 'cheese'. They also make glue from Casein.

"nightjar" > I mean the plastic that a bit like the old bakelite.

Errm, 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.

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.

Indeed.

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).

they used a different and stronger plastic due to the sliding cover mechanism. Although of course this may not apply to all makes.