what does that mean? im not familiar with that phrase.
Polymers have several characteristic temperatures associated with them.
- One is the melting temperature, the temperature at which material will flow.
- another is the "heat deflection temperature", the temperature at which, if subjected to a certain pressure the material takes a permanent deformation (flows) .
- yet one more temperature is the glass transition temperature, the temperature below which a plastic is a glassy solid that cannot flow at all. It can break, but it cannot flow.
of these temperatures, the glass transition temperature is the lowest and the melting temp is the highest. The heat deflection temperature lies between.
Engineers often use polymers at temperatures above the glass transition temperature, but below the heat deflection temperature. This practice is normally OK because the pressures involved are relatively low, so there is not a great enough combination of heat and pressure to allow the material to flow (permanently deform).
Nylon, when used under pressure and below the heat deflection temperature, can flow (take a permanent deformation). Because it is below the heat deflection temperature, it is called "cold flow" but it still takes a couple of hundred degrees and and a few thousand pounds per square inch of pressure to cause it to happen.
No plastic will so deform when used below its glass transition temperature. Since the glass transition temperature of the Nylon polymers used in FRN is at least 120F, this cannot occur. (different Nylon polymers have different glass transition temperatures. The lowest is ~120F) Even if left in the car and subjected to 150F, you would need a couple of tons of sustained pressure at that temperature to cause the Nylon to deform.
There are manufacturing defects that can cause Nylon to deform in one's pocket, but it would be due to a manufacturing defect (cold die, too short a dwell time, etc) rather than cold flow of the Nylon.
