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Crumbling Choc Block!

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Evenin' All,


 A first for me today. Never before seen. I was removing an old brown three terminal choc block that had been recessed into a very old lime mortar brick wall inside a house. The cable ran to an outside high level light. When I removed the choc block it just crumbled like seaside rock. I couldn't believe just how brittle it was. It was only supplying a single outside light mounted on a wooden back mounting block. No overheating evident. 


P.S. Add. The outside wooden mounting block for the light was screwed to the outside wall. The installer was a boat builder so the wood is probably marine grade "teak" or similar. Could the wood have given off fumes that worked their way through the hole in the wall to the chock block insulation and attacked it?


The cause? Chemical reactions?


Ideas please.


Z.


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  • 0
    mapj1:

    how old - the very early choc block, the stuff that actually snapped like chocolate, was Bakelite, and so hard and brittle, but nor crumbly.  I am wondering about some rubber formulation, or maybe some sort of thermoset cast resin. But by maybe mid 1960s it would all be nylon or polyethylene, for reasons of cost.

    There a no readily available chemicals that turn nylon crumbly, but  the effects of various agents on different plastics are summarised here 

    Mike


    Yep, the stuff is very hard and brittle. I am used to the strength of Bakelite, this stuff that  came I across is 20 times more brittle than Bakelite. It cracks when you just look at it.


    Z.


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  • 0
    mapj1:

    how old - the very early choc block, the stuff that actually snapped like chocolate, was Bakelite, and so hard and brittle, but nor crumbly.  I am wondering about some rubber formulation, or maybe some sort of thermoset cast resin. But by maybe mid 1960s it would all be nylon or polyethylene, for reasons of cost.

    There a no readily available chemicals that turn nylon crumbly, but  the effects of various agents on different plastics are summarised here 

    Mike


    Yep, the stuff is very hard and brittle. I am used to the strength of Bakelite, this stuff that  came I across is 20 times more brittle than Bakelite. It cracks when you just look at it.


    Z.


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