50 years of SIGRAFLEX® -
Unrivalled Sealing

With SIGRAFLEX you know what you get.
Safety. Quality. Reliability.

The SIGRAFLEX story begins in 1972 with the inauguration of our first flexible graphite foil line in Meitingen, Germany, and the SIGRAFLEX brand registration. Since then, our brand and products have conquered the world wherever safety, quality and reliability of the sealing materials are required.

From then to now, our SIGRAFLEX flexible graphite materials, SIGRAFLEX carbon and graphite yarns and, most importantly, our SIGRAFLEX people, make the difference by delivering the ultimate solutions for sealing and high temperature applications.

When buying SIGRAFLEX, our customers and the end users know what they get.

Opening ceremony of the first SIGRAFLEX production plant in Meitingen, Germany, 1972

Join us on our journey through the last five decades and read about the SIGRAFLEX history.

1972-2022: Milestones in 50 years of SIGRAFLEX

From the start, SIGRAFLEX established itself as the quality leader in the market of flexible graphite products. With our two production sites located in Meitingen, Germany and Valencia/CA, USA we ensure supply safety for our customers all around the world. Our SIGRAFLEX people always strive to provide products meeting the highest standards of long-term stability, quality, and safety and are pleased to share their technology expertise.

Since 1972, many new and innovative SIGRAFLEX products have set benchmarks for high-end graphite sealing solutions – from SIGRAFLEX UNIVERSAL to SIGRAFLEX HOCHDRUCK, followed by SIGRAFLEX MF® and SIGRAFLEX APX2® up to the TA-Luft compliant PRO variants and our SIGRAFLEX APX2 yarn.

Then and still today, SIGRAFLEX stands for Unrivalled Sealing.

  • The early days: Development of a new unique graphite material

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  • Official opening of first SIGRAFLEX® production plant
  • Registration of SIGRAFLEX® brand
  • New sealing material for difficult operating conditions

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  • SIGRAFLEX® portfolio grows and gains in relevance
  • First large-scale foil order comes from Japan

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  • SIGRAFLEX® NORMAL: First graphite gasket sheet with metal reinforcement

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  • Polycarbon Inc. becomes part of SIGRI

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  • SIGRAFLEX® STANDARD: First anti-stick graphite gasket sheet
  • Foundation of the Valencia site
  • SIGRAFLEX® UNIVERSAL: Reinforced gasket sheet with anti-stick coating

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  • Commissioning new 1,000 mm (39.4”) wide plant in Meitingen, Germany

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  • Start of production of 60“ (1,524 mm) wide foil line in Valencia, USA

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  • SIGRAFLEX® HOCHDRUCK: Graphite gasket sheet meets highest demands for sealabilty and mechanics

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  • "Northridge" earthquake stops production in Valencia, USA, only for a short time:
    operations resume after only one month of downtime

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  • Commissioning of 1,500 mm (59.1“) wide foil line in Meitingen, Germany
  • Granting of SIGRAFLEX® HOCHDRUCK patent

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  • SIGRAFLEX® MF®: Gasket sheet for minimum leakage, best anti-stick behavior and safety

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  • SIGRAFLEX® APX2® foil: Best-in-class temperature and oxidation resistance

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  • Inauguration of 2nd production line in Meitingen, Germany

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  • Great SIGRAFLEX team effort enables restart of production in foil manufacturing facility in Meitingen, Germany, just three months after a fire

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  • SIGRAFLEX® APX2® HOCHDRUCK: Gasket sheet for high temperature applications

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  • SIGRAFLEX® APX2® yarn: Maximum protection from oxidation
  • SIGRAFLEX®: High purity – best protection from flange corrosion

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  • The newest SIGRAFLEX® product innovation

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Latest SIGRAFLEX® product innovation:
SIGRAFLEX iNXT graphite gasket sheet with innovative antistick surface finish

Operators of chemical, petrochemical and power plants, as well as gas suppliers need gaskets that enable safe operation, reduce emissions, and lower total operating costs. Special requirements are placed on both leak tightness, on the one hand, and anti-stick properties are essential, on the other hand. A good gasket release is key, i. e. removing the gasket with as little residue as possible to keep maintenance work short and costs low.

This year, at ACHEMA 2022, the SIGRAFLEX Sales team was able to present a product innovation: The new SIGRAFLEX iNXT stainless steel-reinforced gasket sheet, which features a special surface finish that improves antistick properties, and a next-generation impregnation to reduce leakage.

SIGRAFLEX products have a long history of providing the best possible release behavior from the flange. Since the launch of SIGRAFLEX UNIVERSAL in 1983, SGL Carbon has offered reinforced SIGRAFLEX gasket sheets on the market with an antistick impregnation. Over time, many other sheet products have been added that also feature this type of surface finish, such as SIGRAFLEX STANDARD, HOCHDRUCK, HOCHDRUCK PRO, UNIVERSAL PRO and SELECT. As they are better in terms of antistick properties then comparable products in the industry, well-known end users have been using these materials ever since.

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In 1998, the SIGRAFLEX sheet portfolio was expanded to include SIGRAFLEX MF. A special and unique product, for its production a new antistick technology was developed. To this day, it is the best-in-class material when it comes to minimum leakage (TA Luft compliance), best separating behavior, maximum safety, and process cleanliness.

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Nevertheless, the SIGRAFLEX team does not rest on its laurels: always with the aim of offering customers added value, the team works continuously to develop new products or improve existing ones, and to identify new materials and manufacturing processes.

The work of Jürgen Bacher and Thomas Kirschbaum with the energetic sales support of Martin Reinthaler and Rainer Zeuß finally led to success once again.

Surface coating and finishing has always been a dominant topic in SIGRAFLEX development, and with SIGRAFLEX iNXT we were able to expand the portfolio to include a TA Luft compliant gasket sheet with an alternative antistick technology. This gives our customers an even more comprehensive choice from which to select the optimum product for their application.

SGL Carbon offers the broadest and high-quality graphite sheet portfolio in the market, which best serves the diverse needs of end users.


SIGRAFLEX® APX2® yarn: New development in demand offers maximum protection from oxidation

Since Polycarbon Inc. became a part of the company in 1980, packing yarns have been part of SGL Carbon’s portfolio of sealing materials. Initially, it consisted exclusively of carbon and graphite textile yarns (also known as fiber or filament yarns). These were then produced from rayon, pitch and polyacrylonitrile fibers as starting materials.

Packing yarns are relatively soft, pliant fibers which are braided into various shapes and sizes. The resulting products, so called braided, compression or stuffing box packings are processed into packing rings, which are the oldest and still most common sealing devices. They are used in various industries like chemical and petrochemical, pulp and paper, power plants or marine, and seal all types of fluids e. g. in valves, pumps, mixers, and agitators.

Pitch yarns were taken out of the program over the years, but foil yarns were newly added as complement. Since, SGL Carbon has always been the quality leader with the broadest portfolio in the flexible graphite foil market. So, it was naturally to add a wide selection of foil yarns, too.


Photo: SIGRAFLEX APX2 yarn for oxidation resistant braided packings

Foil yarns are made from graphite foil tapes that are interwoven with fibers or wires for reinforcement. Materials used for reinforcement include cotton, glass fiber, stainless steel, synthetic fibers or carbon fiber.

As early as the 2000s, SGL Carbon offered a wide range of foil yarns with different reinforcements. The development work was carried out both in the Research & Development department at our German site in Meitingen and at our Yarns Competence Center in Valencia/CA, USA. At that time, our Sales was increasingly approached by customer requests for high-temperature resistant and at the same time high-purity braided packings with excellent mechanical properties.

Initiated by Andrew James und Mike Römmler, the focus of the yarn development work in the early 2000s was increasingly placed on the production of foil yarns with Inconel®* 601 as reinforcement. Inconel® 601 is a nickel chromium iron alloy that is extremely resistant to temperature and corrosion. It is, so to speak, an ideal partner for the SIGRAFLEX® APX2® foil launched in 2004, the best-in-class graphite foil when it comes to temperature and oxidation resistance.

In 2015, the new SIGRAFLEX APX2 flexible graphite foil yarn, made from SIGRAFLEX APX2 foil with Inconel 601 wire reinforcement, was ready for the market. It was presented to the general public at ACHEMA 2015 as the foil yarn offering maximum protection against oxidation.

To this day, SIGRAFLEX APX2 foil yarn impresses with its unmatched performance: resulting from a combination of low friction, flexibility, resilience, purity and excellent media resistance. Because it is manufactured without binders or adhesives, it does not become brittle. And due to its high thermal conductivity, heat generated by friction can be dissipated quickly and safely. And the wire reinforcement provides additional tensile strength as well as pressure and extrusion resistance.

Without doubt, graphite in its various forms is responsible for extending the performance of the packed gland. With the use of SIGRAFLEX APX2 foil, SGL Carbon pushed back boundaries once again and set new standards for oxidation and media resistance and mechanical properties.

With the addition of the foil yarn, the SIGRAFLEX APX2 product family already included three different products, all of which stand for maximum oxidation protection. In 2020, another family member was launched: SIGRAFLEX APX2 coating for packings.



* Inconel® is a registered trademark of Special Metals Corporation


New graphite gasket sheet for high temperature applications

SGL Carbon's most important goal is to offer users real benefits with its products. One cornerstone for achieving this goal is the continuous development and introduction of new sealing products with unique properties. This has set SGL Carbon apart from the competition since the early days of the SIGRAFLEX business.

Great successes have already been achieved in the past with the combination of unique product properties: In the 1980s, for example, Research & Development engineers combined the metal reinforcement of SIGRAFLEX NORMAL with the antistick coating of a SIGRAFLEX STANDARD sheet to create the new gasket sheet SIGRAFLEX UNIVERSAL.

New opportunities arose in the 2000s after the flexible graphite foil SIGRAFLEX APX2, developed at the site in Valencia/CA, USA, was successfully placed on the market due to its best-in-class temperature and oxidation resistance.

Then as now, SIGRAFLEX HOCHDRUCK and HOCHDRUCK PRO were and are very popular products with customers and in high demand due to their excellent tightness and mechanical strength. However, both sheets have their limitations when it comes to application temperature. At that time, European gasket manufacturers and their customers, the plant operators, in particular asked for improved solutions for higher process temperatures.

So, the Sales team in Meitingen discussed the idea of trying to meet these customer requirements by combining two established products again: To use the extremely temperature resistant SIGRAFLEX APX2 foil for producing various proven sheet products. The properties of one combination product proved to be particularly convincing.

In close cooperation with the Meitingen Operations and R&D department and the R&D colleagues in Valencia, a new unique sheet product was created: SIGRAFLEX APX2 HOCHDRUCK, being at the same time the first Meitingen/Valencia or German/US SIGRAFLEX combination product.

The sheet combines the outstanding characteristics of both SIGRAFLEX APX2 graphite foil and reinforced sheets manufactured with the unique SIGRAFLEX HOCHDRUCK technology. It is therefore of high-strength and extremely resistant to temperature and oxidation.

Users in the process industry can reliably and safely seal almost their entire range of flat gasket applications with the help of SIGRAFLEX APX2 HOCHDRUCK, which can be used at operating temperatures from -269 °C to +580 °C (452 °F to +1076 °F); depending on the flange design and lifetime expectation.

SIGRAFLEX APX2 HOCHDRUCK is specially designed for sealing joints subject to high mechanical load. The sheet can also be used in all common flange constructions, in pipelines and vessels, for example in chemical and petrochemical industries and in refineries.

Metal reinforced graphite gasket sheet with anti-stick coating – in use until today

Over the years, graphite gasket sheets became SIGRI's special core competence. The research and development department in Meitingen was constantly looking for solutions to the sealing problems of the industry. Efforts were directed both to the development of new innovative products and to the improvement of existing ones.

The idea was to combine the respective unique properties of the metal reinforcement of SIGRAFLEX NORMAL and the anti-stick coating of SIGRAFLEX STANDARD in a new product. Silvia Mechen and Alfred Hirschvogel in particular worked intensively on the development of this product combination and the SIGRAFLEX UNIVERSAL gasket sheet was born.

In 1983, the product was presented to customers and end users at ACHEMA for the first time, and its success took off from there. SIGRAFLEX UNIVERSAL is still state of the art and to date one of the most important products in our portfolio.


Fire in the Meitingen SIGRAFLEX® production

In a fire in the SIGRAFLEX foil production in Meitingen on August 16, 2011 fortunately no one was injured. The blaze however destroyed large parts of the production plant and the building. While the western area of the tower was spared with the exception of a few plant and steelwork components, the entire eastern area had to be restored.

The whole SIGRAFLEX team in production, sales, customer service and product group worked at high pressure not only to rebuild the plant, but at the same time to maintain delivery capability and thus not cause any bottlenecks for our customers.

While the team of the SIGRAFLEX foil production manager, Anton Wittmann, in Meitingen started reconstruction work as soon as possible, the SIGRAFLEX colleagues at the site in Valencia/CA, USA, led by Brian Green, immediately took over part of the production of the European products. And the European sales team worked closely with customers to find solutions to compensate for the loss of production in the best possible way. Many meetings were held to coordinate the demands for the next few months and to discuss the possible postponement of orders and deliveries of material made in the USA.

Rosa Lindenmayr from the Customer Service Team and Rainer Zeuss for Sales are particularly worthy of mention. They were "soild as a rock", kept close contact with customers, coordinated the required quantities with Valencia and constantly updated and coordinated delivery schedules. Despite the greatest stress and pressure, they always maintained their positive thinking and optimistic attitude.

The steel structure of the new tower was largely completed by the end of the year. The destroyed parts of the facility were rebuilt and partially replaced with improved equipment.

Thanks to the great efforts of the colleagues the production in Meitingen had been restarted already by mid-November 2011, and by the end of the year was again covering large parts of the product portfolio.

One year after the fire, the facility had been completely rebuilt and modernized with cutting-edge technology.

Once again, this crisis situation showed that SIGRAFLEX's success is not only based on brand and product, but on the motivation and commitment of our employees. Thanks to this great team effort, the support of numerous areas of the SGL Group site in Meitingen and above all the loyalty and flexibility of our customers. SIGRAFLEX has emerged from this situation stronger than ever.


Inauguration of 2nd flexible graphite production line in Meitingen

In addition to its established business in graphite sealing materials, where SGL Carbon continued to be the market leader in the 2000s, as well as intensively developing new products and driving growth, the company was also looking for other applications for products made of flexible graphite.

Werner Guckert played an important role in the New Business Development team at that time. It focused on application areas that benefited from the excellent thermal and electrical conductivity of flexible graphite, such as thermal energy storage systems and air conditioning in buildings.

These products are still part of the flexible graphite portfolio of SGL Carbon: ECOPHIT® graphite lightweight boards for radiation ceilings and SIGRATHERM® graphite products like powder, sheets, high-density foils and graphite/PCM composites for thermal management.

The development of the new businesses made a capacity expansion of the Meitingen flexible graphite production necessary. In December 2008, the time had finally come and the second production line for flexible graphite in Meitingen was ceremoniously commissioned.

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Two new SIGRAFLEX® graphite sheet products: Launch of the UNIVERSAL PRO and HOCHDRUCK PRO product variants for TA Luft applications

Since industrialization in the 19th century, the environment has been increasingly burdened - by pollutants and noise. For this reason, regulations on keeping the air and other environmental media clean and protecting against noise were already enacted in Germany, among other countries, at that time. Over the years, these regulations have been continuously developed and supplemented by additional requirements.

In 1964 e. g. the "First General Administrative Regulation on the Federal Immission Control Act", short Technical Instructions on Air Quality Control or German Clean Air Act (TA Luft), came into force. Currently, the scope of application of the TA Luft covers more than 50,000 facilities in Germany that require a permit.

Since then, the TA Luft has been amended several times, always in connection with a tightening of the immission requirements, i. e. the limit values for pollutants that may be discharged into the air. The new version of TA Luft in 2002 posed a particular challenge to the producers of sealing materials, as the emission limits were significantly reduced.

The SIGRAFLEX Research & Development department in Meitingen worked very intensively on improving the leak tightness of SIGRAFLEX sheet products in order to be able to offer customers materials that also met the requirements of the new TA Luft. And finally with great success: In 2003, SGL Carbon first launched the new adhesive-free and TA Luft-compliant graphite gasket SIGRAFLEX SELECT.

This was followed just two years later by SIGRAFLEX UNIVERSAL PRO, a further development of the proven UNIVERSAL sheet, and finally in 2006 by HOCHDRUCK PRO. "PRO" stands for TA Luft compliance, which is achieved by a special impregnation resin. The development work on the PRO variants had been led by Jürgen Bacher and Oswin Öttinger.

UNIVERSAL PRO was first presented to the general public in 2005 at the ISGATEC trade fair in Nuremberg, both PRO products were then exhibited together at ACHEMA 2006.

And it was not only in the reduction of leakage through impregnation that major progress was made during this time: As early as 1998, another major breakthrough was made in improving the properties of SIGRAFLEX gasket sheets. The process developed and patented by SGL Carbon for the overlap-free laser welding of stainless-steel foils made it possible to manufacture flat steel reinforced gasket sheets with dimensions of up to 1,500 mm x 1,500 mm without leakage channels for one-piece gaskets with a maximum diameter of 1,500 mm. Silvia Mechen, Manfred Jung, Hubert Malik, Oswin Öttinger and Bernd Schellenberger played a major role in the development of the process at that time.

This meant that large SIGRAFLEX HOCHDRUCK sheets, which had already been on the market since 1997, could now be offered in the butt-welded version. The 1,500 mm x 1,500 mm sheet portfolio comprising SIGRAFLEX UNIVERSAL and HOCHDRUCK was then joined in the mid-2000s by the PRO variants, because size also matters when it comes to keeping the air clean.

SGL Carbon currently offers a broad portfolio of different graphite gasket sheets that meet the maximum requirements of the German Clean Air Act (TA Luft), even after its revision, which came into force in 2021: In addition to the three products mentioned above, there are SIGRAFLEX MF®, EMAIL and our latest product SIGRAFLEX iNXT. In addition, SIGRAFLEX HOCHDRUCK, APX2 HOCHDRUCK and ECONOMY are also suitable for certain TA Luft applications, depending on material thickness and gasket stress.

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SIGRAFLEX® APX2® foil: Best-in-class temperature and oxidation resistance

From the beginnings, SIGRAFLEX flexible graphite foil was used successfully as a sealing material in automotive applications. The first mass product were cylinder head gaskets due to the foil’s ability to easily adapt to uneven surfaces and its suitability for highly automated gasket manufacturing.

SGL Carbon’s R&D department at its US site in Valencia/CA had continuously worked on even improving the foil’s oxidation resistance. The engineers Mike Roemmler and Tim Burnett together with their colleagues intensified those activities in the 1990s. Automotive OEMs had strongly requested more resistant graphite sealing materials to also meet the rigorous demands of modern exhaust systems. Among other things, they tested various oxidation inhibitors, formulations, and concentrations to find the optimum solution.

The result of the group’s work was finally launched in 2004: The unrivalled best-in-class oxidation and temperature resistant graphite foil SIGRAFLEX APX2®. Its typical weight loss of only 0.6% per hour in air at 670°C (1238 °F) is still unmatched. It allows for producing e. g. exhaust gasket rings, exhaust manifold gaskets, exhaust gas recirculation (EGR) gaskets or diesel particulate control (DPC) / filter (DPF) gaskets of the highest quality. The first customer who sold SIGRAFLEX APX2 gaskets to the market was the Japanese company Oiles Corporation.

SIGRAFLEX APX2’s performance advantages are not only valued by the automotive industry but are also essential for high-temperature

industrial sealing where durability, reliability, and safety are of critical importance – no matter if used for producing packing rings, spiral wound, Kammprofile, or flat gaskets.

SGL Carbon’s proprietary production process allows to incorporate an oxidation inhibitor directly into the structure of the graphite foil, which best optimizes SIGRAFLEX APX2's oxidation resistance behavior.

Since SIGRAFLEX APX2 is such a unique product, it offered even more options for product innovations, so that the APX2 family should continue to grow over the years.


SIGRAFLEX® MF®: Gasket sheet for minimum leakage, best antistick behavior and safety

End users are familiar with this situation: maintenance work is due, and the flat gasket sticks to the flange when it is replaced. If possible, without damaging the flange, the gasket then has to be removed by hand in a laborious and time-consuming process. However, downtimes are an extreme cost factor in every plant and for every operator. The aim is therefore to keep maintenance work as short as possible.

Since the 1980s, SGL Carbon has done research to find coatings which improve the release properties of the SIGRAFLEX graphite sheet surface.

The first major success was achieved with an antistick impregnation. The first product on the market equipped with this technology was SIGRAFLEX STANDARD. Over the years, numerous other antistick graphite sealing sheets followed for which SGL Carbon uses this technology, such as the SIGRAFLEX SELECT, UNIVERSAL or HOCHDRUCK. Until today, impregnated SIGRAFLEX graphite sheets have been used by many well-known chemical companies because of their superior antistick properties.

In the 1990s, SIGRAFLEX research also focused on the development of new graphite sheets with particularly low leakage, i. e. highly tight products. For this purpose, special attention was paid to materials that had already proven themselves as sealing materials, and their use and performance in combination with graphite foil was investigated.

The work of Silvia Mechen and Otto Mederle, initially led by Mike Roemmler and later by Oswin Oettinger, eventually resulted in a completely new product with unique properties: SIGRAFLEX MF®.

SIGRAFLEX MF is a three-component gasket sheet made of SIGRAFLEX flexible graphite foil, stainless steel and PTFE foil. The sheet combines the outstanding sealing properties of the three materials in one product. It is the only sheet, which offers minimum leakage (TA Luft compliant) at best antistick behavior and safety.

Owing to its SIGRAFLEX flexible graphite foil core it displays high long-term stability, and adapts well to uneven flanges. The stainless steel reinforcement – the sheet is available with steel foil or tanged steel enforcement – ensures the high mechanical strength of the gasket. Due to the stainless steel/PTFE top layers, SIGRAFLEX MF separates with ease from flanges and leaves no residue. With SIGRAFLEX MF nothing sticks to the flanges, whether at room temperature or at 300 °C (572 °F). Moreover, the top layers together with an inner eyelet provide excellent sealing properties.

There is no time-consuming cleaning of the flanges when using SIGRAFLEX MF. Maintenance time and the risk of scratching the flange faces reduces significantly. The end user saves time and money with every gasket change.

The launch of SIGRAFLEX MF in 1998 thus marked a milestone in the ability to reduce both emissions and total cost of ownership through the use of graphite flat gaskets. To this day, the sheet is best-in-class when it comes to tightness and antistick properties at temperatures up to 300°C. It also meets high requirements for process hygiene and product purity (FDA compliance) and can therefore also be used in the pharmaceutical and food industries, for example.

Back in 1999, SGL Carbon also filed a patent application with the European Patent Office for the SIGRAFLEX MF layer bond and the eyeleted gasket. Both patents were granted in 2004 (Metal reinforced graphite laminate; Laminate seal with edge member).


Granting of HOCHDRUCK patent

Developing new SIGRAFLEX products has always been primarily geared to the requirements of our customers and users, but of course we also always keep an eye on the latest developments in regulations. Our Research & Development departments have put a lot of effort and innovative force into this work over the years – from the Head of R&D to the engineers and lab technicians at both our sites in Valencia and Meitingen.

Copy patent applications are essential to protect our ideas, new technologies and products from imitation and copying. Those also help maintaining the market value of our products and our overall business success, our reputation and offer competitive advantages to our customers.

Especially the unique SIGRAFLEX HOCHDRUCK technology developed in the early 1990s in Meitingen, i. e. the method to produce high-strength adhesive-free layer bonds of highly pure graphite and stainless-steel foils, needed patent protection.

Till today, SIGRAFLEX HOCHDRUCK’s performance is best-in-class when it comes to leak tightness under high pressure. SGL Carbon had filed the application at the European Patent Office in 1994 and the patent was then granted in 1996 (Method of making a layered metal and graphite product).

Additionally, in 1996, SGL Carbon launched two new SIGRAFLEX sheet products, SIGRAFLEX EMAIL and SIGRAFLEY ANTISTICK:

  • SIGRAFLEX EMAIL is a TA Luft compliant gasket sheet made of SIGRAFLEX high-purity flexible graphite foil reinforced with two layers of flat stainless-steel foil using the HOCHDRUCK technology. The sheet was developed especially for use in PTFE envelope gaskets e. g. for enamelled pipe work and vessels or steel pipework in the pharmaceutical industry.
  • SIGRAFLEX ANTISTICK is a gasket sheet made from flexible graphite reinforced with tanged stainless-steel and equipped with a special mineral-based antistick finish to improve handling and scratch resistance.

Commissioning of 1,500 mm (59.1“) wide foil line in Meitingen, Germany

In the late 1980s to the early 1990s, the asbestos ban became effective in various European countries, which also affected fiber gaskets based on asbestos. Gaskets made of flexible graphite come closest to the application properties of asbestos in terms of temperature and chemical resistance. So, the ban further boosted the demand for graphite-based sealing materials - and thus for products made of flexible graphite.

The SIGRAFLEX® production plant commissioned in Meitingen in 1986, which could manufacture foils up to a width of 1,000 mm, had already reached its capacity limits at that time. Furthermore, requests from European customers for larger-format SIGRAFLEX products accumulated. Such products had already been successfully produced since 1988 at our Valencia production site in the US with the 1,500 mm (59.1”) wide foil line (see 1988 milestone). With the existing equipment the increasing demand could no longer be satisfied.

As a result, a project team in Meitingen, headed by Günter Gabriel, the then SIGRAFLEX Production Manager, began planning the construction of an also 1,500 mm wide foil line. It was finally put into operation in 1996. A foil width of 1,500 mm is still state of the art today.

The first new products that were manufactured on this line were presented to a wide audience at the ACHEMA in Frankfurt in 1997, including a 1,500 mm x 1,500 mm printed SIGRAFLEX HOCHDRUCK gasket sheet and a one-piece SIGRAFLEX HOCHDRUCK flat gasket with a diameter of 1,500 mm.


Northridge earthquake hits Valencia production:
Joint efforts make resuming operations after only one month possible

In the early morning hours of January 17, 1994, an earthquake hit the greater Los Angeles area. The so-called Northridge earthquake was of the magnitude 6.7 and had a duration of 10-20 seconds. It killed more than sixty and injured more than 9,000 people and made many homeless. It caused widespread damage: Collapsed or heavily damaged buildings, crumbled freeways, power outages, broken water and burst gas pipelines some of which also caught fire, etc.

Even at distances more than 250 miles (400 km) away from the epicenter in the San Fernando Valley, the shaking was felt. The quake covered an area of more than 200,000 square kilometers of the land of the United States and Mexico.

Also, the City of Santa Clarita, located 35 miles (55 km) northwest of the City of Los Angeles and the location of our US site (Valencia is a neighborhood in Santa Clarita) was heavily affected.

Our SIGRAFLEX production came to a halt. Cleanup and repair work were started as soon as it was safe to enter the site again. With the joint efforts of all site employees, it was possible to put the main equipment into operation again after a downtime of only four weeks.


World novelty SIGRAFLEX® HOCHDRUCK: Adhesive-free graphite gasket sheet with flat stainless-steel reinforcement for highest demands on tightness and mechanics

As early as the 1980ies, the tanged, impregnated graphite gasket sheet SIGRAFLEX® UNIVERSAL had already established itself on the market - as a high-performance product for sealing pipelines and vessels in chemical, petrochemical and power plants, among others.

However, for applications requiring thinner gaskets, used e. g. in valves and pumps, the market at that time also asked for flat steel reinforced graphite sheets. These also have the advantage of being easier to process.

In 1991, SIGRI launched SIGRAFLEX ECONOMY, the first flat stainless-steel reinforced, bonded gasket sheet, which, like UNIVERSAL, is still state-of-the-art today and an important part of our portfolio.

In the next step, the SIGRAFLEX R&D team, led by Alfred Hirschvogel, worked on developing a layer bond between graphite and steel in which the adhesive does not lead to a reduction of the maximum permissible gasket stress.

Silvia Mechen in particular concentrated on this task and, after many test series, was finally able to announce success in 1993: The new unique SIGRAFLEX HOCHDRUCK technology was born!

It creates a high-strength adhesive-free layer bond of highly pure graphite and stainless-steel foils. HOCHDRUCK sheets are rated to 250 bar (3625 psi) and meet the most stringent leak-tightness demands. The flat gaskets are also extremely safe and reliable. HOCHDRUCK is still one of the top products in our portfolio and continues to deliver what its name promises.

Throughout the 1980s and 1990s, SIGRI's engineers not only worked to create new products with other unique features, but also to further develop existing products in order to offer customers even better performance and service.

A major step was taken with the successful development of a process for sheet printing. In addition, a color logic was defined specifically for this purpose: Each SIGRAFLEX sheet is printed with a different color and also the exact sheet type and can thus be clearly identified. This enables end customers to avoid the use of wrong materials and thus to better prevent accidents.

The 1990s saw changes not only in SIGRAFLEX products but also at SIGRI. Through numerous acquisitions and investments, the company had developed into a group of companies, the SIGRI Group, since 1967. At the beginning of 1989, Hoechst AG took over the group completely.

Hoechst strived for making the SIGRI business more global and gaining more market power. On February 6, 1992, a merger with the U.S. company Great Lakes Carbon Corp. took place: the birth of the newly founded company Sigri Great Lakes Carbon GmbH - SGL Carbon for short - was announced.


Start of production of 60'' (1,524 mm) wide foil line in Valencia

Since the foundation of the Valencia site in 1983 the demand for graphite foil especially by the automotive industry had increased constantly. This was a big opportunity for Polycarbon to further grow its business - especially in North America, but the capacity of the existing equipment had already been at its limits. Therefore, Polycarbon took the decision to build a new foil line in Valencia to significantly increase the capacity and participate in this market growth.

In 1988, the most technologically advanced and sophisticated flexible graphite foil line at these times called "Ultraline" was taken into operation. It made Polycarbon and its parent company SIGRI the only manufacturer in the world being able to offer 60 inch (1,500 mm) wide graphite foil.

The production process was computer driven and utilized automatic monitoring systems to tightly control impurity levels, thicknesses, densities, and area weights – all vital characteristics of Polycarbon’s graphite foil, sold under the CALGRAPH brand at this time. The new equipment allowed Polycarbon to produce the highest quality flexible graphite in the market.

By 1990, the foil production in Valencia had already doubled.


Commissioning of a new 1,000 mm (39.4”) wide calender roll line in Meitingen

The mid-1980s saw a sharp increase in demand for flexible graphite foil - driven mainly by the sealing industry. The material's environmental friendliness and being harmless to health also played a vital role. At that time, gaskets containing asbestos fibers were often used for applications at higher temperatures and against aggressive. Therefore, the sealing industry was looking for non-carcinogenic materials with comparable properties to replace asbestos. Flexible graphite was seen as the ideal solution being fiber free, temperature and corrosion resistant and non-carcinogenic.

SIGRI was already seen as the market leader for graphite foil in Europe. In Meitingen, the plant’s capacity had already been increased several times and was producing a maximum of 160 metric tons per year, with the calender roll line being the limiting factor.

SIGRI was already seen as the market leader for graphite foil in Europe. In Meitingen, the plant’s capacity had already been increased several times and was producing a maximum of 160 metric tons per year, with the calender roll line being the limiting factor.

The calender rolls compact the expanded graphite flakes without the addition of binders or fillers and roll them into foils or sheets. At that time, the foil line allowed a maximum foil and sheet width of 500 mm (19.7”).

From around 1984, this capacity was no longer sufficient as the market demand was much greater. Therefore, in early 1985 the SIGRI management approved the construction of a new calender roll line in Meitingen. By November 1986 it was already in operation.

The new roll line offered significant advantages: It was not only twice as fast, but also twice as wide: Foil and sheets with a width of 1,000 mm (39.4”) could be produced. In addition, the line was equipped with the latest technology of the time. It operated almost fully automatically and was electronically controlled and monitored. This helped to further improve the already excellent quality of SIGRAFLEX.

With its commissioning, SIGRI was therefore ideally prepared to serve the fast-growing market and, at the same time, to consolidate and even further expand its own strong position as market leader.


SIGRI brings SIGRAFLEX® STANDARD, the first anti-stick graphite gasket sheet, to the market

In the 1980s, SIGRI's ambition remained unchanged to develop further innovative sealing materials based on flexible graphite that would provide real benefits to users and give SIGRI an edge over the competition.

Sealing points equipped with graphite gaskets do not stick or weld, i. e. the flanges can be removed even after a long period of operation. However, gaskets sticking to the flange faces is a major problem. Residues have to be removed and the flanges have to be cleaned by hand, which costs time and money. In addition, there is a great risk of damaging the flange surfaces, for example with a wire brush or spatula.

Therefore. the developers at SIGRI looked for a coating of the foil surface that would reduce sticking and make the surface less sensitive to scratches, thus easier to handle. The result of the development work came onto the market in 1983: the impregnated homogeneous gasket sheet SIGRAFLEX STANDARD.

Foundation of the Valencia site

In 1983, SIGRI’s US subsidiary Polycarbon founded a new site in Valencia, California to be able to further grow its business as especially the demand for graphite foil used in the manufacture of cylinder head gaskets and exhaust gaskets for the automotive industry grew.

All manufacturing and business activities were relocated from North Hollywood, CA to Valencia. This included not only the fabric and yarn production but also the 12" (30.5 cm) wide graphite foil line and all accompanying equipment.

Metal reinforced graphite gasket sheet with anti-stick coating – in use until today

Over the years, graphite gasket sheets became SIGRI's special core competence. The research and development department in Meitingen was constantly looking for solutions to the sealing problems of the industry. Efforts were directed both to the development of new innovative products and to the improvement of existing ones.

The idea was to combine the respective unique properties of the metal reinforcement of SIGRAFLEX NORMAL and the anti-stick coating of SIGRAFLEX STANDARD in a new product. Silvia Mechen and Alfred Hirschvogel in particular worked intensively on the development of this product combination and the SIGRAFLEX UNIVERSAL gasket sheet was born.

In 1983, the product was presented to customers and end users at ACHEMA for the first time, and its success took off from there. SIGRAFLEX UNIVERSAL is still state of the art and to date one of the most important products in our portfolio.


Polycarbon Inc., the exclusive representative for graphite foil in USA, becomes part of SIGRI

After having already started the regional expansion to North America in 1975 with exporting flexible graphite foil to the US, the time had come in 1980 to intensify those activities and to grow the business with flexible graphite foil, therefore SIGRI acquired the company Polycarbon.

Polycarbon Inc., established in 1967, was owned by Pat Sterry. The company sold carbon and graphite products e. g. to the heat treating, aerospace, automotive and sealing industries.

It was a well-known manufacturer of woven carbon-based fabrics sold e. g. to the Space Shuttle program and carbon and graphite yarns for braided packings. The yarns as a different type of sealing material were an ideal complement to SIGRI's graphite foil.

Since the beginning of exporting graphite foil from Meitingen, Germany, Polycarbon had been the exclusive representative for processing and selling SIGRI's flexible graphite foil in the US. At its California facility the foil was further processed into packings and corrugated tapes which were sold under the CALGRAPH brand.


Product innovation from SIGRI introduced to the market:
SIGRAFLEX® NORMAL, the first graphite gasket sheet with reinforcement

After commissioning the first foil line in Meitingen, engineers worked constantly to improve the manufacturing process as well as to develop new products. In particular, the idea of producing a graphite sealing sheet with higher mechanical strength was intensively pursued.

At the end of the 1970s, the SIGRI engineers - most notably Alfred Hirschvogel - succeeded in producing tanged stainless-steel sheets that could be used to reinforce graphite foils. In this graphite-metal gasket composite/laminate, the flexible graphite takes over the sealing function whereas the metal reinforcement increases the strength and facilitates the handling of the gasket.

Thus, in 1979, the first reinforced graphite gasket sheet was introduced to the market. The product known as SIGRAFLEX NORMAL consisted of an adhesive-free lamination of two graphite foils and a tanged stainless-steel reinforcement.


The SIGRAFLEX® portfolio grows and gains in importance

SIGRI Sales continuously looked for further fields of application for SIGRAFLEX® but whilst the R&D department also worked on broadening the product portfolio.

In 1974, the SIGRAFLEX portfolio already consisted of graphite foil products (SIGRAFLEX F), laminates (SIGRAFLEX L) and expanded graphite (SIGRAFLEX E):

  • Foils were used to produce flat gaskets and packing rings. For flat gaskets with large diameters, foil is superior to other materials because overlapping joints can be pressed together to form a homogeneous gasket and thus have no weak points at the joints.
  • For the manufacturing of laminates, several foil layers were pressed together without the use of a binder. The laminates are stiffer than the foils, but otherwise they have the same properties. SIGRAFLEX L was recommended to produce gland packings as well as thermal insulation and electric heating elements.
  • SIGRAFLEX E was mainly used for producing molded parts.

First large-scale order for SIGRAFLEX foil for cylinder head gaskets for a new Honda Civic model

In 1974, SIGRI ELEKTROGRAPHIT received the first large scale order for flexible graphite foil from the Japanese gasket manufacturer Nippon Leakless. The order volume was 30 t of foil per year. Nippon Leakless processed the foil in Japan into cylinder head gaskets for a new engine with a different combustion configuration for the Honda Civic.


Cylinder head gasket made from SIGRAFLEX flexible graphite foil


A new sealing material especially suitable for difficult operating conditions

Carbon and graphite were used as dynamic sealing materials long before the industrial production of graphite foil, e. g. for seal rings or mechanical seals, packing or metal-sleeved rings. However, they could not be utilized for static sealing applications. This changed with the availability of flexible graphite foil. The material's softness and flexibility, aging and corrosion resistance, low permeability, and smooth pressure and temperature change behavior make it ideal for both static and dynamic sealing applications.

After the successful development of SIGRAFLEX in the laboratory, SIGRI began to look intensively for possible applications for the material and quickly realized that it could have great potential as a sealing material - due to its unique properties.

Read an article about flexible graphite seals, published in Chemical Processing in October 1973:

Learn more

Excerpt from the contents of the advertisement:
To ensure that nothing leaks, SIGRAFLEX® gaskets own properties no other gasket material can match: Temperature resistant, -200 °C to +3000 °C, no corrosion, no aging, no flowing, no embrittlement and offer excellent long-term stability of compressibility and recovery at low sealing forces and excellent pressure resistance.

Registration of the SIGRAFLEX® brand

On October 4, 1972, SIGRI Elektrographit GmbH filed an application for the SIGRAFLEX trademark with the German Patent Office in Munich. The list of goods in this application now also included the various sealing materials – in contrast to the old application from 1969.

Even today, after 50 years, the brand is still recognizable and known globally in the sealing world far beyond the borders of Meitingen. SIGRAFLEX has and still stands for high-quality materials made of flexible graphite.

Ceremonial SOP of the first SIGRAFLEX plant in Meitingen

The successful laboratory trials for the production of flexible graphite foil and the great market interest triggered by the presentation at the “Hanover Fair” led to an intensification of research activities at SIGRI ELEKTROGRAPHIT.

In 1969, Head of Research Dr. Otto Vohler gave the go-ahead for the development of a manufacturing process for flexible graphite. Fritz Wagner was responsible for the project planning of the first foil line. In 1971, the first foil line, named “Akropolis”, was put into operation by the research team headed by Dr. Peter-Ludwig Reiser. The ceremonial commissioning of the line took place in Meitingen on April 28, 1972.

The plant, with a capability of producing foil at a width of 500 mm (19.7”), initially had a capacity of 10 metric tons per year. This was very quickly increased to approximately 25 metric tons per year. With the demand constantly increasing through the 1970’s particularly for the sealing industry, the pilot plant was converted to a full production unit. Dr. Ottmar Rubisch was the first Head of Operations at this time. By 1985 the plant was capable of producing 160 metric tons of foil per year.

Prior to 1972
The early days of SIGRAFLEX

Development of a new graphite material with unique properties

In fact, the history of SIGRAFLEX begins even before 1972. The space race that started with the flight of the first artificial earth satellite Sputnik 1 by the Soviet Union in 1957 and with the increasing need for lightweight and extremely temperature-resistant materials also inspired the research and development activities at the then Siemens Plania AG. Carbon-based materials seemed to be ideally suited for this purpose. The company thought it had a good chance of success in serving many industrial applications too and creating a new pillar for the company.

At the beginning of the 1960s, a large number of projects were therefore launched with the aim of producing new so-called special materials from carbon and graphite. Numerous materials that were deemed suitable – were pyrolyzed, e. g. threads, fabrics and felts. This gave rise to the new products carbon and graphite felts, carbon threads and fibers, carbon fabric, foamed carbon and glassy carbon.


Photo: ZDF, one of Germany’s major TV stations, filming at the SIGRI booth at Hannover Messe trade show in 1969.

At SIGRI ELEKTROGRAPHIT, the new company formed in 1967 after the merger of the carbon activities of Farbwerke Hoechst and Siemens Plania, another unique graphite material also awakened the interest of the researchers: flexible graphite. Under the guidance of Gernot Hochegger, amongst others, a whole range of new products including SIGRAFLEX flexible graphite foil was developed.

In 1969, SIGRI ELEKTROGRAPHIT presented all the newly developed special materials to a wider audience for the first time at the Hannover Messe (“Hanover Fair”), one of world's largest trade fairs mainly dedicated to the topic of industry development. In particular, the impact of a television report on ZDF, one of Germany’s major TV stations, in which the new products were presented, was significant and exceeded all expectations. This generated great interest in the new materials and a huge number of visitors to the fair. To handle the many inquiries, a new sales organization called SOKO was even founded with the aim of pushing the launch of the new products and exploring the economic potential.


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