Adhesive-free sealing systems - technological development for increased safety and sustainability

LE-SAFE lamella seal from IDT for triple-eccentric butterfly valves (Image source: IDT Dichtungstechnik)

The use of adhesives in industrial sealing technology is widespread, but increasingly brings with it safety, hygiene and environmental challenges. New technical approaches show that these problems can be avoided by making design changes - by dispensing with adhesives altogether. The following article sheds light on the background, technological details and possible applications of adhesive-free sealing systems.

The production of industrial seals is increasingly the focus of safety, hygiene and environmental requirements. In the conventional production of composite seals, adhesives are often used as bonding agents between metallic carrier materials and soft materials such as graphite. However, this practice is associated with several technical and safety-related disadvantages. Adhesives usually consist of hydrocarbon-based components and contain additional substances such as propellants.

Seal comparison of a glued comb profile seal vs. LE-SAFE (Image source: IDT GmbH)

Technical challenges when using adhesives

In processes where purity, chemical stability or thermal stability are crucial, this can lead to considerable problems.

In areas such as the food and pharmaceutical industries, there is a risk that adhesives could release undesirable substances into the product. There is also an increased risk in applications with pure oxygen or oxidizing media, as some adhesives are prone to spontaneous combustion under certain conditions. In addition, contact with metallic components can trigger corrosion processes that have a negative impact on the integrity of the seal. The ageing and limited temperature resistance of some adhesives can also shorten the service life of the seal and lead to unplanned maintenance measures or failures.

Adhesive-free joining technology represents a technical advancement in the sealing sector. (Image source: AdobeStock / Vlyaks)

Adhesive-free connection technology as a solution

A technical approach that completely dispenses with the use of adhesives was implemented with the development of an adhesive-free sealing system. In this system, metallic carriers are mechanically bonded with pure graphite. The connection is made without the use of chemical bonding agents and remains stable against mechanical stress and thermal loads. The tightness, deformation behaviour and mechanical properties of the seals produced in this way correspond to those of conventionally bonded systems. At the same time, there are improvements in setting amounts and relaxation behaviour, which means that the behaviour of the seal remains stable over longer periods of time.

The design of such seals also allows them to be used in sensitive applications such as oxygen-carrying systems. The Federal Institute for Materials Research and Testing has examined the reaction behaviour towards oxygen and confirmed that no increased risks arise from the sealing system. The temperature stability of the graphite material used corresponds to that of pure graphite foil, which was confirmed by thermogravimetric analyses. This means that it can also be used in high-temperature applications or under highly fluctuating temperature conditions.

Another aspect relates to sustainability and material management. The absence of adhesives makes it easier to separate the materials used at the end of the product's life, which is particularly advantageous in terms of recycling and disposal concepts. As no volatile organic compounds are released, the impact on people and the environment during production and use is also reduced. From a business point of view, the increased resistance to thermal and mechanical influences can also lead to a longer service life, which can reduce maintenance costs.

Overall, the adhesive-free connection technology represents a technical advancement that responds to current requirements in sealing technology. It can be used in various industrial applications, for example in piping systems, pumps, flange connections or butterfly valves with special geometric requirements. The availability of reliable test values for leakage, modulus behaviour and temperature stability enable reliable design and calculation in accordance with applicable standards. This makes it possible to replace existing sealing systems with adhesive-free alternatives without having to compromise on proven performance features.