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® 9 Welcome to the Next Generation of Sealing Technology
PTFE Products - Sigma™
Flexitallic Sigma offers outstanding chemical resistance while the unique manufacturing process results in a biaxial-
ly fibrillated structure ensuring high seal integrity in the most demanding applications.
Pure PTFE sheet products are highly susceptible to creep relaxation which can be reduced by the incorpora-
tion of selected fillers (Filled PTFE). The maximum reduction in creep is achieved by combining these fillers in a
biaxially orientated structure such as Sigma.
Flexitallic Sigma materials are inherently clean, making them suitable for use in industries where product con-
tamination may be of concern such as food, pharmaceuticals and electronics. The components of the Flexitallic Sigma
range comply with the requirements of FDA regulations and the materials’ outstanding chemical resistance make them
suitable for sealing virtually every chemical medium across the whole pH range (1 - 14).
Sigma products give unparalleled levels of sealing performance, especially when compared to conventional
materials used in applications involving aggressive chemical media. These comparisons are supported by data gen-
erated by recognized, independent, international bodies in the field of static sealing. Sigma products are ideally suit-
ed for applications where seal integrity is paramount, an important consideration where stringent emission controls
may be in force.
All products in the Flexitallic Sigma range are capable of sealing from cryogenic temperatures up to 260°C
(500°F). For intermittent use even higher temperatures can be tolerated. Pressures from 8.5 MPa (1230 psi) down to
vacuum can be accommodated. Furthermore, applications involving low gasket stresses such as glass lined, plastic
and ceramic flanges, will not result in loss of sealing performance. These typically relate to the use of glass lined,
plastic and ceramic flanges.
The Sigma range of products has been engineered to be user
friendly:
• Materials can be cut easily using conventional tools and
techniques
• Complex geometric shapes can be accommodated,
including narrow cross sections
• Gaskets are easy to install and remove
• All products are non-toxic
Product Range
Sigma 500 - Sheet material with higher compression specifically formulated for use on glass lined, plastic or ceram-
ic flanges. Also suitable for use on flanges which are non-parallel, damaged or distorted. Compatible with acids and
alkalis at all but the highest concentrations. Enhanced compressibility is achieved by the incorporation of hollow
glass microspheres as the inorganic filler.
Sigma 511 - Standard compression sheet material reinforced with a silica filler. Intended for use with concentrated
acids (except hydrofluoric acid) and with most general aggressive chemicals: also suitable for medium concentrations
of alkalis.
Sigma 522/577 - These products have rigid cores of biaxially reinforced PTFE with soft, conformable surface layers
of pure PTFE. Designed for use where low bolt loading is available.
Sigma 533 - Standard compression sheet material reinforced with barytes (barium sulphate) filler. Sigma 533 is the
preferred choice for sealing concentrated alkalis and is also compatible with Aqueous Hydrofluoric Acid. Restricted
resistance to concentrated mineral acids.
Sigma 588 - Most compressible PTFE sheet containing no filler; biaxially orientated PTFE core with surfaces of high
yet controlled compression.
Sigma 599 - Specially formulated PTFE sheet with hollow glass microspheres for higher compression.