The melt viscosity of PTFE film is very high, and the melt viscosity is 1010Pa·s at 380°C.
The melt viscosity decreases with the increase of shear stress, showing its non-Newtonian fluid flow characteristics.
In fact, the melting of PTFE film is completed within a wide temperature range, which is related to the processing conditions of PTFE.
New, unsintered ptfe begins to melt near 340°C and is completely melted above 355°C; while the sintered material starts to melt around 327°C when the temperature rises again, and is completely melted at 343°C.
In addition, ptfe also has “cold flow properties”, which brings certain limitations to its application.
For example, when PTFE is used as a sealing gasket, the bolts are tightened so tightly that when the specific compressive stress is exceeded, the gasket will produce “cold flow” (creep) and be flattened.
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