"TeflonŽ" is the registered trademark of the DuPont Company for its
fluorocarbon resins. DuPont pioneered the use of TeflonŽ PTFE and FEP resins following
the discovery that they could be made into articles having a combination of mechanical,
electrical, chemical, temperature and friction-resisting properties unmatched by articles
made of any other material. TeflonŽ fluorocarbon resins' unique combination of physical,
electrical, and chemical properties have found application in nearly every field of modern
industrial, scientific, and technological endeavor.
PTFE
Structurally, there are different types of TeflonŽ resin. TeflonŽ PTFE resin is a
polymer consisting of recurring tetrafluoroethylene monomer units with the formula:
(CF2-CF2)n
The maximum molecular weight of this greater than 90°/0 crystallinic TFE Polymer is about
9x106. PTFE displays a series of unique properties:
Nearly universal chemical resistance (exceptions: elemental fluorine, CF3, molten alkali
metals) Insoluble in all solvents below 300°C High service temperature stability up to
250°C Very low adhesiveness Very low friction coefficient Extremely hydrophobic
Physiologically inert, contaminant free Very good electrical (high resistance) and
dielectrical (very low dielectric number and loss factor) properties Nonflammable Highly
weather resistant (UV resistant) Good mechanical properties: tough elastic, easily
manufactured
These advantages of PTFE, especially its universal chemical resistance, are the reason
labware and accessories made of PTFE or other fluorocarbon resins are a must in any
laboratory. Its broad service temperature range and its unbreakability are further
advantages of PTFE.
Stirrer blades, magnetic stir bars encapsulated in PTFE, joint sleeves, adapters and
boiling accessories are just a few of the items available in PTFE along with standard
Labware items such as
Flasks, Bottles,
Beakers, etc. They are
indispensable if the chemical resistance of glass or rare metals does not suffice.
Digestion in boiling hydrofluoric acid or boron trifluoride is possible as well as hot
alkali-hydroxide melts.
Labware made of PTFE resists temperatures of -200°C without becoming brittle. The maximum
service temperature is +250°C, (but 300°C is possible) for a short time period. PTFE is
extremely nonadhesive. This is an advantage for working with lacquers, adhesives, resins
and hydroscopic substances. PTFE is biologically inert. Therefore it is used in many
applications in biology, microbiology, medicine, pharmacy and in the food industry.
Pure PTFE, because of its chemical resistance and its antiadhesive surface, prevents any
sample contamination by abrasion or etching. Vessels made of PTFE therefore are absolutely
necessary in trace element analysis methods.
The production of PTFE-ware is performed using the so called isostatic pressing process.
PTFE powder is filled in forms and isostatically pressed at high pressures. The pressed
parts are sintered at temperatures up to 400°C. The characteristics of the material are
substantially influenced by the pressing and sintering process. Porous PTFE is made by
controlled sintering of powders with defined particle sizes. Stock PTFE in rods, sheets,
etc. are available for customer use. PTFE : TeflonŽ,
Hostaflon, Malon, Fluon, Polyflon
FEP
Similar properties are displayed by the Tetrafluoroethylene Hexafluoropropylene-copolymer
FEP: [CF(CF3)-CF2(CF2-CF2)n]m
The molecular weight of this copolymer is 50,000 to 500,000 and the crystallinity is about
50%. The maximum service temperature of 205°C is lower than PTFE. FEP is
thermoplastically moldable (injection molded at temperatures of 320°-360°C extruded at
350°C - 410°C) is translucent, flexible, and feels heavy because of its high density. FEP
: FEP-Resin. TeflonŽ. N fl- n
PFA
Perfluoroalkyoxy-polymers, PFA has the same advantages as PTFE TeflonŽ with the
structure: [CF(OR,)-CF2(CF2-CF2)n]m OR, represents a perfluoroalkoxy group.
PFA can be melt processed (extruded). The chemical resistance is comparable to PTFE. PFA
is translucent and slightly flexible. It has greater mechanical strength and higher
temperature tolerance than PTFE. Its melting temperature is 305°C.
"PFA was first used in the semiconductor industry for injection molded wafer carriers
and similar articles that resisted aggressive chemicals and high temperature chemical
processing. Now, PFA is also considered to be the best TeflonŽ for semiconductor piping
applications, and is accepted for both liquid reagents and UPDI water handling in advanced
processlng appllcations." PFA : TeflonŽ PFA
Reference: Burggraaf, P., Semiconductor International, July 1988, p.55.
