SIGRAFLEX® flexible graphite for gaskets and packing rings

What is flexible graphite?

Flexible graphite – also known as expanded graphite or exfoliated graphite – is produced from purified natural graphite flakes.

In the manufacturing process the flakes are mixed with a highly oxidizing acid to produce graphite intercalation compounds. These are expanded by a sudden application of high temperature. The resulting product called expanded graphite is mechanically compressed to shaped products, mainly to graphite foil. Although still showing the unique properties of natural graphite e.g. its excellent conductivity, expanded graphite foil is also flexible, soft and easy-to-process in contrast to the raw material.

SGL Carbon offers a broad range of SIGRAFLEX flexible graphite foil grades for different applications. They feature high reliability, even under extreme operating conditions. Thus, they are the first choice for sealing applications for long-term use at high temperatures.

Industrial manufacturing processes are becoming more and more complex, and more demanding on the materials used. In particular higher process temperatures, reductions in equipment downtimes, and increased product quality demand optimum material solutions. SIGRAFLEX foils made of expanded natural graphite support end users around the world in producing high quality products for safe processes.

Long-term stability of compressibility and recovery over a wide temperature range
Range of use from -269 °C (-452 °F) to approx. 3,000 °C (5,432 °F) depending on installation and operating conditions
Low permeability to gases and liquids
Absence of binders means no ageing or embrittlement
High resistance to chemical media and radiation

With our support, select exactly the product which most closely meets your requirements from the largest portfolio of flexible graphite foils and tapes in the world: For example, oxidation resistant, high-purity or industrial quality foils or grades that exhibit low friction characteristics.

Long-term stable mechanical behavior

All of our foils and foil tapes are distinguished by their long-term stability. This is a crucial benefit and stands in contrast to other materials exhibiting high flow characteristics which is detrimental to the long-term integrity of a joint seal. Even when surface stress reduces during operation, the sealing effect of SIGRAFLEX is largely maintained.

Processing of graphite foils and tapes

SIGRAFLEX flexible graphite foils and foil tapes have an outstanding workability and are particularly easy to cut, to press and to punch. They are processed into a wide range of products by using various methods.

Flexible graphite foil is found particularly in flat gaskets and as graphite outer layer for Kammprofile and corrugated gaskets, but also in high temperature processes as heating element, heat shield, release liner, protective liner and diffusion barrier.

Foil tapes are pressed to packing rings, wound into spiral wound gaskets, processed into foil yarns for braided packings or into corrugated tapes.

We offer the best flexible graphite foil for your individual application.

		Foil type
Application		APX2	BP	AP	APX	E	SHL	C	B	A	N	Z	ZX	AQ	TF	S
Chemical and petrochemical	Spiral wound gaskets	●	●		●	●	●	●	●			●
	Kammprofile	●	●		●	●	●	●	●			●
	Corrugated gaskets	●	●		●	●	●	●	●			●
	Packing rings	●	●		●	●	●	●	●			●	●	●	●
Power generation	Spiral wound gaskets	●	●		●	●	●				●	●				●
	Kammprofile	●	●		●	●	●				●	●				●
	Corrugated gaskets	●	●		●	●	●				●	●				●
	Packing rings	●	●		●	●	●				●	●	●	●	●	●
Refining	Spiral wound gaskets	●	●		●	●	●					●
	Kammprofile	●	●		●	●	●					●
	Corrugated gaskets	●	●		●	●	●					●
	Packing rings	●	●		●	●	●					●	●	●	●
Automotive	Gaskets in exhaust system	●	●	●	●
Automotive	Cylinder head gaskets	●	●	●	●					●

SIGRAFLEX flexible graphite foils and foil tapes made of expanded natural graphite are distinguished by their high temperature resistance. They are the first choice in sealing applications for long-term use at high temperatures.

Compared to other industrial graphite foils, our types SIGRAFLEX APX2, BP, AP, APX and E exhibit remarkable oxidation resistance. Their typical weight loss (in TGA test in air at 670 °C (1,238 °F) for four hours) is at 2% per hour and less, while conventional industry foils lose up to 40%.

When it comes to corrosion protection, SGL Carbon offers the widest-ranging portfolio on the market. With their low sulfur and halogen content, our foils fulfill user specifications and are genuine high performers in system protection.

Typical properties	Unit	APX2	BP	AP	APX	E
Thickness	mm	0.25 - 1.52	0.25 - 3.05	0.25 - 2.0	0.35 - 1.0	0.35 - 1.0
Thickness	in	0.01 - 0.06	0.01 - 0.12	0.01 - 0.08	0.014 - 0.04	0.014 - 0.04
Purity	%	≥ 98	≥ 98	≥ 98	≥ 98	≥ 99
Ash content	%	≤ 2	≤ 2	≤ 2	≤ 2	≤ 1
Density	g/cm³	1.0 - 1.12	0.7 - 1.43	1.0 - 1.12	0.7 - 1.3	0.7 - 1.3
Sulfur content	ppm	< 300	< 300	< 300	< 300	< 300
Chloride content	ppm	≤ 25	≤ 50	≤ 50	≤ 25	≤ 10
Weight loss in air at 670°C/1238°F (TGA)¹⁾	%/h	≤ 1	≤ 2	≤ 2	≤ 3	< 4

SIGRAFLEX flexible graphite foils are manufactured without the use of adhesives and binders. We use high-purity natural graphite flakes as our base material. This minimizes contamination which significantly reduces the leakage rate, as well as the thermal and corrosion resistance of graphite gaskets and steel flanges.

Thanks to its very high-purity SIGRAFLEX foils make a significant contribution to protecting adjoining components from corrosion. This increases the operating reliability and the entire service life of equipment. Our products contribute significantly to cutting costs in static and dynamic sealing connections, piping, pumps, fittings, and vessels. Our high-purity foils are especially suited to extreme requirements, such as sensitive processes in power plants.

Typical properties	Unit	N	Z	ZX	S
Thickness	mm	0.25 - 1.52	0.15 - 3.0	0.37	0.25 - 1.52
Thickness	in	0.01 - 0.06	0.006 - 0.12	0.015	0.01 - 0.06
Purity	%	≥ 99.5	≥ 99.85	approx. 98	> 99
Ash content	%	≤ 0.5	≤ 0.15	approx. 2	< 1
Density	g/cm³	0.7 - 1.12	0.7 - 1.3	0.95	1.12
Sulfur content	ppm	< 300	< 300	< 300	< 300
Chloride content	ppm	≤ 50	≤ 10	≤ 20	≤ 10

Our SIGRAFLEX industrial quality foils boast outstanding sealing properties. They are compressible and easy to shape and fit well against the surface to be sealed, even on uneven surfaces, a clear advantage over other sealing materials.

Typical properties	Unit	C	B
Thickness	mm	0.35 - 3.0	0.25 - 3.0
Thickness	in	0.014 - 0.12	0.01 - 0.12
Purity	%	≥ 98	≥ 98
Ash content	%	≤ 2	≤ 2
Density	g/cm³	0.7 - 1.3	0.7 - 1.4
Sulfur content	ppm	< 300	< 500
Chloride content	ppm	≤ 25	≤ 50