Frequently Asked Questions (FAQs)

Flat gaskets are typically placed between two flanges or sealing surfaces and secured with screws or bolts that pull the parts together and compress the gasket. It is important that the gasket is correctly aligned and the correct tightening torques are used to ensure even compression and an effective seal. The service life of flat gaskets depends on the material, operating conditions and type of application. For example, rubber gaskets can wear out due to aging and UV exposure, while metallic gaskets last longer in high-stress areas. Regular inspections and timely replacement are crucial for long-term functionality.

For many special sealing requirements, seals and profiles made of FKM (fluoro rubber) are the material of choice. High-quality FKM, which is manufactured by DuPont under the material name Viton®, for example, is indispensable, especially in areas where work is carried out at high temperatures or where the seals come into contact with aggressive chemicals or oils. Not all FKMs are the same; special manufacturing processes, additives and, above all, the fluorine content in the material have a significant influence on the quality.

The term fluororubber (abbreviation FPM according to DIN/ISO or FKM according to ASTM) refers to a whole group of rubbers that have vinylidene (di)fluoride (VDF) as one of their monomers as a common feature. Fluororubbers were developed in the 1950s by DuPont (as Viton). Today there are a number of other companies that offer FKM.

The different qualities are reflected in the temperature behavior, the resilience and the resistance to chemical substances. There are high-quality FKMs that can easily withstand 96% sulfuric acid at temperatures of up to 250 °C.

Less special FKMs tend to lose their “attitude” at times.

Classic FKM is a relatively solid material. What is desirable in some applications limits its usability in others. REXIO GmbH & Co. KG offers a solution here with Vi/MoosFlex seals and profiles made of foamed FKM, so-called fluorofoam rubber, which supplements the relatively dense, solid fluoro rubber (density 1.7 - 2.2 g/cm3, Shore hardness 55 °A - 90 °A) with a soft material (density approx. 0.8 g/cm3, Shore hardness between 20 °A and 30 °A) with the same excellent thermal and chemical properties.

Overall, the selection and processing of FKM, Viton® and Vi/MoosFlex seals and profiles, as well as their bonding and professional assembly, is a complex topic. Developers, buyers and users who are not familiar with the topic in detail should ensure that they receive expert and good advice when selecting their supplier in order to avoid unpleasant surprises later on in use.

Do you know the difference between foam rubber and cellular rubber? Foam rubber and cellular rubber are made from the same raw materials, often EPDM, CR, NR, NBR or SBR. However, due to different manufacturing processes, the material structure of foam rubber and cellular rubber differs fundamentally.

Foam rubber has a mixed cell structure with predominantly open cells and a dense outer skin. Cellular rubber, on the other hand, has a closed cell structure without an outer skin. Foam rubber is made of extruded rubber, has open cells and a dense outer skin. In the area of foam rubber profiles, there are basically two manufacturing methods: molded foam rubber and extruded foam rubber profiles. For both methods, the surface of foam rubber profiles and seals is better protected from external influences than with cellular rubber due to the dense, robust and elastic outer skin. However, if the surface is damaged, the foam rubber seal with the open cell structure can absorb watery medium through capillary action.

Cellular rubber has no outer skin, which makes the surface more sensitive and easier to damage. The porous but closed-cell structure, however, means that watery media cannot penetrate. Cellular rubber seals are therefore practically water and airtight.

The sealing power of high-quality foam rubber such as Moosflex, cellular rubber and Dioflex is similar. Moosflex foam rubber profiles and foam rubber round cords from REXIO, like Dioflex sealing tape made of cellular rubber, have a high degree of elasticity under pressure combined with a particularly good recovery capacity. The profiles cling tightly to all surfaces under light pressure and thus seal.

The right compression is what matters!

REXIO seals made of foam rubber and cellular rubber seal best with a compression of 30% to 50%. Compression of the material over 50% should be avoided. Both foam rubber and cellular rubber profiles and seals can be damaged in the structure by compression of over 50%, which can lead to reduced resilience.

Crown profiles should be checked regularly for cracks, abrasion and wear, especially in areas where they are subject to heavy wear. To prolong their life, they should be protected from UV radiation and extreme temperatures. Care should also be taken to ensure that crown profiles do not come into contact with harsh chemicals or solvents unless the material used is suitable.

Edge protection profiles without metal band are usually made of flexible materials such as silicone or TPE, which offer good shock absorption. Edge protection profiles with metal band, on the other hand, are more robust and offer additional protection against mechanical impacts, as the metal band increases stability.

Rigid PVC profiles are products made from polyvinyl chloride (PVC) that have high strength and good dimensional stability. They are often used in building and construction applications. Rigid PVC profiles are weatherproof, durable and easy to maintain. They are resistant to chemicals and UV radiation, making them ideal for indoor and outdoor use.

Elastic, pliable and flexible – these are the typical properties of the material rubber, which everyone knows and which is part of our everyday life in many different forms.

For some time now, however, it has become more difficult to correctly determine the material of many products. There are bicycle handles, water hoses and tires for toy cars, sealing rings and door stops, and they all feel like rubber and are similarly flexible. In fact, however, they are made of "thermoplastic elastomers" (TPE). The similarity to rubber is astonishing. But what are the differences?

Rubber is a rubber product made from natural or synthetic rubber. Rubber is a tough, plastic material that only becomes elastic rubber when cross-linking chemicals such as sulphur or peroxide are added and then heated. In this "vulcanisation process" the thread-like rubber molecules are cross-linked by the formation of chemical bonds. The cross-linking gives the product its elasticity. This vulcanisation process can only be reversed by thermal destruction.

Thermoplastic elastomers (TPEs) behave completely differently. As the name suggests, these materials become plastic when heated (Greek: thermos = heat), but become elastic again when cooled. In contrast to chemical cross-linking in rubber, this is physical cross-linking. In terms of their structure and behavior, TPEs are therefore between thermoplastics and elastomers. They have the easy processing of thermoplastics and the essential properties of rubber. TPEs are also environmentally friendly. Unlike rubber, they can be easily recycled and reused.

TPE abbreviation:

TPEs are divided into 7 main groups based on their chemical structure and are named with additional letters according to the monomer units used according to DIN EN ISO 18064 as follows:

TPE: Thermoplastic elastomers TPA: Polyamide-TPE TPA-EE: TPA, soft segments with ether and ester bonds TPA-ES: TPA with polyester soft segments TPA-ET: TPA with polyether soft segments TPC: Copolyester-TPE TPC-EE: TPC, soft segments with ether and ester bonds TPC-ES: TPC with polyester soft segments TPC-ET: TPC with polyether soft segments TPO: Olefin-TPE TPO-(EPDM+PP): Ethylene/propylene/diene+ polypropylene TPO-(EVAC+PVDC): Ethylene/vinyl acetate+polyvinylidene chloride TPS: Styrene-TPE TPS-SBS: Styrene/butadiene block copolymer TPS-SIS: Styrene/isoprene block copolymer TPS-SEBS: Styrene/ethenebutene/styrene block copolymer TPS-SEPS: Styrene/ethenepropene/styrene block copolymer TPU: Urethane TPE TPU-ARES: Aromatic hard segments, polyester soft segments TPU-ARET: Aromatic hard segments, polyether soft segments TPU-AREE: Aromatic hard segments, soft segments with ether and ester bonds TPU-ARCE: Aromatic hard segments, polycarbonate soft segments TPU-ARCL: Aromatic hard segments, polycaprolactone soft segments TPU-ALES: Aliphatic hard segments, polyester soft segments TPU-ALET: Aliphatic hard segments, polyether soft segments TPV: TPE with cross-linked rubber TPZ: Other TPE

Our standard production program for silicone profiles offers a variety of shapes and geometries. This enables us to manufacture different silicone profiles. These include profile geometries without defined hollow chambers as well as cross-sections with varying hollow chamber dimensions. These can be manufactured as foam or solid silicone, with a Shore hardness of 15° to 90° Shore A and similar to any RAL color.

In addition, silicone profiles are platinum or peroxide cross-linked and can be made from any material in our range by adding various additives to the raw material, which then make the product tear-resistant, heat-stable or self-extinguishing.

We also offer products with appropriate conformities such as food-grade, approved for drinking water, etc.

Silicone foam is generally more expensive than many other foams, particularly due to its special properties such as temperature resistance up to +230 °C as standard and flexibility. However, the higher material costs can be justified by the durability and versatility of the material. In addition, silicone foam can be used in the food industry.

When choosing a hose, several factors should be considered:

• Material: Depends on the liquid or gas to be transported (e.g. chemicals, water, air).

• Temperature: The hose should be suitable for the required operating temperature.

• Pressure: The hose must be able to withstand the maximum working pressure.

• Flexibility: Depending on the application, the flexibility of the hose is important, e.g. for use in tight spaces.

• Length and diameter: The size of the hose should suit the application.

Yes, many cords are suitable for outdoor use, especially those made from rubber or silicone, which are UV resistant and weatherproof. Rubber and silicone cords are usually waterproof or water resistant and are often used in applications where water ingress must be prevented (e.g. in seals or weatherstripping on windows and doors).

An adhesive is used to bond two or more materials together. A sealant (such as silicone) is used to create a seal that protects against water, air or dust, but does not create a structural bond between the materials. Sealants are particularly useful in applications where a flexible, watertight seal is required (for example, in bathrooms or window seals).

We offer our clearance items at a reduced price to reduce our inventory and make room for new products. These are not defective or damaged and may be the result of overproduction or products with slight tolerance deviations.