We have recently introduced the technology and equipment to allow us to process PTFE polymer in-house.
Extensive capital investment on state of the art C.N.C. lathes, as well
as presses and ovens for sintering, give us a complete in-house
capability to produce a wide range of PTFE components, as well as
Our polymers are purchased strictly from world-recognised manufacturers
and include grades such as virgin, glass, carbon and bronze filled, to
name but a few.
We can produce both large and small quantities of machined components;
these typically include PTFE envelopes, valve seats, bellows, chevron
sets and diaphragms.
Having an integrated gasket and PTFE production unit gives us the flexibility to satisfy all of our customers’ needs.
Introduction to PTFE
Since it was discovered more than 50 years ago, new industrial applications of PTFE are found every day.
Thanks to its outstanding physical properties, PTFE is the material choice for a very large variety of products.
PROCESSING OF PTFE
Unlike thermoplastics the viscosity of the gel above the
melting point is too high for PTFE to be processed by traditional
methods (injection or transfer moulding, rotational moulding…). The
process includes three systematic steps:
- Compression of the powder at ambient temperature,
- Slow cooling.
Compression may be carried out by:
- Press moulding = rods, sheets, tubes, billets,
- Isocratic moulding = allowing the near completion of
the finished shape at the moulding stage. With other methods, the three
steps can be carried out in a continuous operation on one machine:
- Ram extrusion = thick wall tubes, spaghetti tubing…
- Paste extrusion = thin wall tubes, spaghetti tubing…
For parts with complicated shapes or tight tolerances
one or several machining operations are necessary. J A Harrison is
especially equipped for machining these semi-finished products by
turning on a lathe (automatic and CNC), milling, drilling, cutting or
The exceptional strength of the carbon fluorine bond and a
high molecular weight – give PTFE a set of outstanding properties:
- Wide temperature use range: -200oC + 250oC
- Resistance to virtually all-corrosive chemicals: the
chemical inertness of PTFE is unique. PTFE is suitable for almost all
chemicals with the exception of fluorine, some flour chemicals and
molten alkali metals.
- Very low coefficient of friction
- Anti-stick properties
- Excellent dielectric properties (independent of both frequency and temperature)
- Good mechanical properties (excellent fatigue resistance, especially in applications involving flexing or vibrations)
- Excellent tensile strength even at low temperature
- Non-ageing properties
- Moisture and U.V. resistance
PTFE is recognised as remarkable in its resistance to
flame. It is classified as a non-flammable material in air, according to
the ASTM D-635 and D-470 test procedures.
PTFE Filled Compounds
In spite of its remarkable properties pure or “unfilled”
PTFE is inadequate for some engineering uses. Mechanical applications
especially require better physical characteristics.
A proper combination of inorganic and metallic fillers will enhance the following factors:
- Creep resistance,
- Wear resistance,
- Thermal conductivity,
- Arc resistance,
- Dimensional stability,
- Electrical isolation
- Electrical insulation
Sheets can be submitted to a surface treatment on one or
both sides which allows bonding to another surface. Max. width : 1500
mm Thickness: 1.5 a 4 mm 0.5 to 25mm Should longer lengths be needed,
skived tape can be supplied in long rolls which can be up to 1500 mm
wide and between 1 and 4 mm in thickness.
- 1.5 metre long rods: On request: 1 metre long moulded rods can be supplied in filled PTFE.
Moulded and Ram Extruded Tubes