PTFE (Release) Properties

The thermal stability of PTFE is exceptional comparing with most of the engineering plastics. It decomposes visibly only when the temperature is higher than 400°C , Lower than 400°C, its mechanical properties do not change even at the high temperature for a long period of time, as its decomposing rate is very slow.
In 400-650°C, C-C bond breaks up and PTFE decomposes into TFE, HFP and octafluorocyclobutane. Only when temperature is higher than 650°C, its paralysis products perfluoroisobutylene.

2 – Mechanical properties at low and high temperature
As the chain of PTFE is stiff, its melt viscosity is very high (up to 1011Pa). PTFE does not  Flow and possesses certain mechanical strength even the temperature is above its melt point. When temperature is below melt point, its mechanical strength quite relate to environment temperature.   

1-  At 260°C, the tensile strength of PTFE is about 50 kg/cm2( 20% of that at room temperature), and its yield strength is about 14kg /cm2(10% of that at room temperature). At 260ºC, PTFE still can bear certain load and its strain is only 5% as loading persure is 18kg/cm2. 

2- PTFE can work at 30ºC for a short period of time ( such as 1 month )without  Pyrolysis taking place, and it can be used at 260ºC under condition of no load low load. for low temperature, PTFE can worked keep flexible down to-253ºC. 

3- PTFE becomes lack of rigidity when the temperature is relatively high. Filler-adding can improves its rigidity. 15%glass fiber adding can increases 200~400% of its rigidity ( in elastic modulus). 

Electric properties  
As fluorine atoms distribute evenly around the C-C bond, PTFE is a highly non-polar material . Not only it possesses excellent electric insulation, but also the property does not be effected by temperature and electric frequency.    

                  High puncture voltage 
                  2mm thick test-Piece            20 kv/mm
                  0.011mm thick test-piece      60 kv/mm
                  25µ thick test-piece              100 kv/mm

Dielectric constant and dielectric loss tangent
                  Dielectric constant 2.0
                  Dielectric loss tangent ~ 2x10
Temperature and electric frequency do not effect on the above two values.

Volume and surface resistance
                  Volume resistance more  than 10 Ohm.cm
                  Surface resistance more than 10  Ohm.cm
As PTFE does not absorb water. Its volume resistance does not change even dipped in water for a long period of time . Its surface resistance does not change also when it is exposed to humid air (relative humidity 100%).

Arc resistance
PTFE has good resistance to arc. When high – voltage discharge takes place on surface of PTFE, there only give off some degraded gases, but no carbonation which means no short circuit.
Even PTFE is exposed to open air over a long time, and contaminated by dust, rain, and fog, its arc resistance would keep no change.

Surface properties of PTFE
The dip-moist property by water and most of the organic liquids is poor.
Only can ether, hexane, petroleum ether, etc. wet its surface .

Anti-adhesion of PTFE
With anti – adhesion to any materials, including adhesive agents, it is widely used in textile and other industries. Surface adhesion can be improved by treating its surface naphthalene – sodium solution or gamma- radiation or glow discharge.

Friction coefficient
In general, friction coefficient between PTFE and metal is in the range of 0.07~0.14.It friction coefficient is nearly as that of ice.
Friction coefficient is low as frictional speed does not surpass 66m/min. The friction coif becomes higher with the increasing of frictional speed. Friction coefficient almost does change at temperature between 20~327ºC. 

Resistance to aging and burning
As there is no photo-sensitive groups in molecule chain of PTFE, it possesses unique aging resistance and oxidation resistance.

Its surface does be with no change even after being exposed to open air for many years There is no need of any anti-agar and stabilizer in PTFE processing.

Oxygen can accelerate the pyrolysis  of PTFE when temperature is higher than 450ºC Below this temperature, oxygen does not obviously accelerate pyrolysis reaction. In normal condition, PTFE will never burn.

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