About PTFE (Polytetrafluoroethylene)
Many of today’s process chemistry, pharmaceutical and biotech laboratories and manufacturing units face an increasing demand to use equipment which is Pure, Chemically Resistant, Cleanable and Durable.
The PTFE Process Chemistry Equipment range is designed to meet the demands of today’s process chemistry operations whilst also providing a versatile and cost effective means for the assembly of a whole range of components in flanged reactors and similar vessels.
PTFE has an unmatchable profile of unique properties which make it one of the most valuable and versatile engineering materials available.
Total Chemical Resistance
The chemical inertness of PTFE is virtually total.
Molten or dissolved alkali metals, such as sodium in liquid ammonia, will abstract fluorine from the molecule to leave a black (carbon) surface finish. At elevated temperature attack by fluorine, some fluorine related compounds, alkali earth and alkali metal oxides and carbonates has been noted.
Both chlorine and bromine diffuse reversibly into PTFE without any apparent chemical reaction.
Completely insoluble with high purity
The polyfluorocarbons, especially PTFE, are normally regarded as completely insoluble. Contamination due to dissolution is not, therefore, an issue when dealing with PTFE.
However, dissolution in materials such as cyclic polyfluorocarbon oligomers at 300ºC. and atmospheric pressure has been recorded. It is also known that other perfluorocarbons, perfluorocarbon ethers, perhalocarbons, sulphur hexafluoride and carbon dioxide will dissolve PTFE under the right conditions of temperature and pressure.
Prime quality PTFE resins are inherently very pure and this level of purity can be translated to the final product using molding methods pioneered by COWIE. The finished products have very high purity coupled with low porosity and correspondingly low levels of extractables.
Exceptional Electrical Properties
PTFE has a range of properties especially relevant to its electrical performance including:
· Extremely high electrical resistance
· Excellent dielectric strength, which is essentially independent of temperature and frequency over a wide range
· Low dissipation factor
PTFE also has good arc and tracking resistance, and high surface resistance.
High Thermal Stability
PTFE has exceptional thermal stability and may be used continuously over the working temperature range.
The thermal behavior of PTFE is complex and the following points should be noted:
· Phase transitions accompanied by significant volume changes at 19ºC. and 30ºC.
· Large and temperature dependent coefficients of thermal expansion
· No easily discernible melting point – the notional melting point is about 328ºC.
· The “liquid” phase has a very high melt viscosity which means that PTFE remains in a rigid gel-like state when “molten”
· Thermal decomposition starts at about 400ºC.
· The degree of crystallinity in the solid is determined by the rate of cooling from the “liquid” phase
Fast Cooling = Low degree of crystallinity
Slow Cooling = High degree of crystallinity
Exceptional Anti-Adhesion Properties.
PTFE has the lowest coefficient of friction of all solid materials and other materials show little or no adhesion to PTFE.
Static and dynamic coefficients of friction are equal so no stick-slip movement occurs.
PTFE is difficult to wet; with a contact angle for water of 126º.
Good Flexural Properties.
PTFE shows excellent flex properties, even in the cryogenic range; at ambient temperature resistance to flex cycles of 106 has been recorded.
Flexural properties are strongly dependent on degree of crystallinity and great care is necessary in the selection of polymer grade and in processing conditions to achieve maximum flex life.