plastic melts?

[Bill N-migration]

I'm looking for a new safe. At what temprature will the plastic around an encapsulated coin melt? At what temprature will a coins change color? Paper will char at 400 degrees.

[Oldtrader3]

Plastics have two temperatures that are important to be aware of. The first is vicat point, which is where the plastic softens, sags and looses mechanical properties. The second is melt temperature where the material becomes liquid. Most plastics will melt well below the ignition temperature of paper (about 435 degrees). Vicat point for some plastics can be as low as 175 degrees farenheit. This lower temperature will damage the slab. Slabs are not good protection against fire. Even a one hour, fire rated safe will damage slabs during that time because it is rated for documents.

[TomB]

Something else to keep in mind is that many fire retardant safes will accelerate any toning on your coins because of the materials built into the safe.

[James_OldeTowne]

A clarification I would ask for is: Does the plastic melt or liquefy at a lower temperature than that which changes a coin's color?

 

Also, I would wonder if a safe buried in the ground would help do away with the heat problem.

 

James

[EZ_E]

 

Also, I would wonder if a safe buried in the ground would help do away with the heat problem.

 

James

 

It would totally depend upon the heat transfer coefficient, i.e. how easily heat is able to conduct. So, of course, the more insulation the better. However, there would be more moisture underground so more silica would need to be used.

[Oldtrader3]

The reason I mentioned Vicat point is that at this lower temperature, plastic molecular cross linking breaks and material loses it's mechanical properties. This may include release of chemicals, corrosive gases or dilute acids that may damage the coin's surface. This Vicat temperature is lower than the temperature required to tone a coin instantly. It will accelerate toning however.