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 Plastic insulation can attack other plastic
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 Return to top of page · Post #: 1 · Written at 8:29:29 PM on 7 July 2013.
GTC's avatar
 GTC
 Location: Sydney, NSW
 Member since 28 January 2011
 Member #: 823
 Postcount: 5263

Not concerning radios as such, but further to the discussion on restoring plastic cases, I have come into possession of a pair of vintage toy telephones made in Japan and dating to the late 1950's or early 1960s. They have been stored in their original box for probably 50 years.

When I opened the box I was greeted by something that I've never seen before: one form of plastic attacking another.

While stored in the box, the curly cords that connect the receivers to their handsets have been in close contact with the plastic cases of the handsets.

As you can clearly see in the photos, the curly cords have dissolved the cases and left them deeply scalloped in the shape of the cords. It's just like a soldering iron has melted the plastic.

Googling around I found some references to the plasticisers used in some cable insulation, over time, attacking other types of plastic, particularly polystyrene. I'm guessing that the plastic used by the Japanese back in the day was a form of, or a relative of, polystyrene.

Has anybody has come across this problem in relation to plastic radio cabinets/cases?

Blue Telephone
Blue Telephone


 
 Return to top of page · Post #: 2 · Written at 9:56:04 PM on 7 July 2013.
Brad's avatar
 Administrator
 Location: Greenwich, NSW
 Member since 15 November 2005
 Member #: 1
 Postcount: 5511

At first I thought, this couldn't be right but there it is in living colour.

If the case of the telephone is made of a styrene-based plastic then that will do it. Polystyrene is not only unstable compared to other plastics but is also brittle and highly susceptible to damage by chemicals such as acetone and perhaps even the chlorine content of the PVC sheathing of the cord.

I remember when black jiffy boxes [for Jaycar (Bill Edge Electronics), Dick Smith and Tandy kits] came out, they used to break like potato crisps. Later versions of these boxes were made of stronger, more flexible and more chemically stable plastics.


‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾
A valve a day keeps the transistor away...

 
 Return to top of page · Post #: 3 · Written at 7:45:05 PM on 8 July 2013.
TV Collector's Gravatar
 Location: Ballarat, VIC
 Member since 4 January 2011
 Member #: 803
 Postcount: 456

I've seen this happen before but not as bad as this. I try not to store any equipment with PVC cables pressed against plastic surfaces to avoid this occurring.

PVC is not a particularly stable plastic and sheds plasticisers as it ages giving the plastic an oily sticky surface. The plasticisers make good solvents as well judging by the ease with which the cables mould themselves into any plastic surface they are pressed into.


 
 Return to top of page · Post #: 4 · Written at 9:51:19 PM on 8 July 2013.
GTC's avatar
 GTC
 Location: Sydney, NSW
 Member since 28 January 2011
 Member #: 823
 Postcount: 5263

I asked about any instances of this problem affecting radio cases and, lo and behold, a crystal set popped up on eBay with a dose of this problem, caused by the earphone cable being wrapped around it.

Granted, the crystal set's plastic case (presumably made in Japan) is probably made from a similar plastic to the toy phones, but it is a radio after all Smile

Transistor Radio


 
 Return to top of page · Post #: 5 · Written at 12:08:33 PM on 10 July 2013.
Wa2ise's avatar
 Location: Oradell, US
 Member since 2 April 2010
 Member #: 643
 Postcount: 725

I've seen this happen with late 50's early 60's AA5 radios. People often wrap the power cord around the plastic cabinet. Leaving the damaged cabinet plastic where it sat.

As annoying as batteries that leak. Why do battery manufacturers insist on putting corrosive carp in batteries anyway. A conspiracy with flashlight manufacturers? Smile


 
 Return to top of page · Post #: 6 · Written at 1:42:37 PM on 10 July 2013.
STC830's Gravatar
 Location: NSW
 Member since 10 June 2010
 Member #: 681
 Postcount: 813

Once had a 14" General TV which was in storage and had a similar problem from the cord getting underneath.


 
 Return to top of page · Post #: 7 · Written at 8:24:33 PM on 22 September 2013.
Airzone's Gravatar
 Location: Maclean, NSW
 Member since 30 May 2008
 Member #: 291
 Postcount: 341


I have had this happen to a little Westinghouse valve radio I bought from the USA. I complained to the seller about not telling me of the burn marks on top, now I realise what had caused it. He thought it was a pattern and supposed to be there,
Peter


 
 Return to top of page · Post #: 8 · Written at 2:18:26 PM on 19 December 2013.
Marcc's avatar
 Location: Wangaratta, VIC
 Member since 21 February 2009
 Member #: 438
 Postcount: 3711

There was and article related to conservation of plastic items, in one of the bigger scientific publications. I may still have a saved copy?

Plastic was considered the indestructible wonder material of the twentieth century....... so wrong. Some loses its plasticiser & becomes brittle with heat... lots of 50's radio cabinets. Bakelite & Catlin seem to be a bit more resilient.

The stuff "Barbie" dolls & such are made of is decomposing, one of the decompositin products is Hydrochloric (muratic) Acid aka "Spirits of salts". This is a chain splitter for "Acrylic" and an catalyst / accelerant for further decomposition.

Its a bit like Nitrocellulose, as used in early films and as a furniture finish. It can self sustain its own decomposition in a variety of situations.

Marc


 
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