In the Laboratory and Chemical Plant
P.T.F.E. is a flourinated synthetic resin made by Du Pont and processed at C.I.P., and has virtually ideal properties for a variety of uses in the chemical, medical and physico-technical fields, viz:
- Universal chemical resistance
- Thermal Stability between -250 and +250°c
- Excellent non-stick properties
- Physiologically safe
ITS MAIN ATTRIBUTE – CHEMICAL RESISTANCE
A chemical resistance table is superfluous where P.T.F.E. is concerned. Highly corrosive agents such as hydrochloric acid, fuming sulphuric acid, nitric acid, hot sodium hydroxide solutions, chlorine gas, hydrazine, nitric oxcides, alcohols, esters, ketones and acid chlorides have no effect whatever on the material. So far, no compound has been found that dissolves P.T.F.E. at a temperature below 300°c. Fluorinated hydrocarbons, compounds very similar, chemically, to P.T.F.E. cause swelling at room temperature, but without destroying it.
P.T.F.E. Reacts chemically with only a very few substances under exceptional conditions:
1. Fused or dissolved alkali metals attack the polymer, causing a brown discolouration. This reaction is utilized to make P.T.F.E. surfaces suitable for bonding.
2. Halogens: Elemental fluorine and chlorine trifluoride do not affect P.T.F.E. at room temperature and under normal pressure. Violent reactions can occur, however, at elevated temperatures and increased pressure.
3. At high temperatures, a reaction with other substances can occur if this should lead to the formation of thermally very stable compounds. For instance, reactions with compounds of alkali and alkaline earth metals, particularly oxides and carbonates, have been observed at temperatures above 350°c.
No water absorbtion is to be observed, even after extended periods of immersion of more than 100 hours.
P.T.F.E. is physiologically inert within the normal operational range of -250 to +250°c, which is an important factor where the pharmaceutical and foodstuff industries are concerned.
In P.T.F.E. the intermolecular forces are of a considerably lower order than in other plastics by virtue of the high bond energy between carbon and fluorine and the low polarizability of the fluorine atoms. it so follows that other substances show little or no tendency to adhere to the material.
Gas And Water Vapour Permeability
The degree of gas and water vapour permeability depends largely on processing conditions, and on conditions the material is exposed to in use. Mouldings having a wall thickness of several millimetres, can be regarded as being impermeable to gas and water vapour when in use.
Service Temperature Range
The thermal stability of P.T.F.E. is exceptionally high compared with other plastic materials. The maximum continous service temperature in any given situation depends on the mechanical stress involved. Under moderate loads (0.1 – 0.2 N/mm2), The upper temperature limit for continous service of P.T.F.E. mouldings is 250°c. In many cases, this temperature may be exceeded for short periods, the maximum being 300°c. P.T.F.E. displays good flexibility and extensibility within the service range (-250 to +250°c). For most purposes, P.T.F.E. is fully efficient, even at boiling temerature of liquid nitrogen (-196°c) no embrittlement occurs, even in liquid helium.
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