Materials for medical applications




Impressive progress is continuously being made in medical research. Ever more sophisticated treatment methods are helping to alleviate or remedy the suffering of many people worldwide. In the field of medical technology, highly complex devices are developed and sophisticated systems are created to assist in the treatment of various diseases or injuries.

Molded rubber parts are highly important in medical technology. They are used there either as a standalone medical product or as a component of medical devices. As devices become more advanced, so do the demands placed on molded rubber parts and the materials used, which are often exposed to extreme temperatures and aggressive chemicals or medications. 

Molded rubber parts in medical technology

Molded rubber parts are used in various applications in the field of medical technology. Detailed examples and explanations can be found in our blog entry Rubber parts in medical technology. However, due to the relevance for this entry, we would like to mention some examples again:

For example, there are individual parts or assemblies with which humans do not come into direct contact, but which nevertheless play a critical role in their well-being. Diaphragms, rubber valves, seals or hoses are core elements of pumps used in medical technology, for example in hospitals. Diaphragm pumps, for example, are used to analyze gases and are found in medical autoclaves, which are used to sterilize and disinfect materials and objects. In other pumps, rubber parts ensure that patients reduce the risk of pressure sores (bedsores) through the use of air beds, that fluids are pumped, that ventilators supply sick people with sufficient oxygen, or that dentists can propel dental tools and aspirate fluids. Also, handles of surgical instruments and tools are often made of silicone due to its excellent medical properties.  

Then there are articles that are used in devices with which the person has direct skin contact. Here again, one can differentiate whether these devices come into contact with the person for a short time or whether they are worn on the body or inside the body.

Plasters made of silicone, for example, are used in the treatment of wounds. Wound spacers ensure that wound dressings do not stick to the wound and that dressings can be changed without pain. Rubber parts are used in hearing aids in the form of seals, microphone suspensions or receiver suspensions, thus helping to improve the quality of life of people with hearing disorders. Diabetes patients, on the other hand, have the option of wearing insulin pumps and thus being supplied with insulin on an ongoing basis. Like the pancreas, the insulin pump delivers insulin to the person and thus takes over diabetes management. Regular injections are no longer necessary and the patient's blood sugar can be regulated in a stable manner.

Rubber parts appear as implants in various places in the human body. In orthopedics, for example, silicone plays a role in the use of artificial joints. In urology, silicone bladder catheters are used that are equipped with a silicone balloon (so-called balloon catheters). While the catheter itself drains urine from the bladder, the balloon serves to stabilize the catheter in the urethra. In the field of epilepsy treatment, vagus nerve stimulators can be implanted whose outer sheath and insulation are made of silicone. The same applies to deep brain stimulation, which is used, for example, in the treatment of Parkinson's disease. The term brain pacemaker is well known in this context. Silicone is also used for insulation in cardiac pacemakers. Silicone anchors can be used to anchor or connect the electrodes of a pacemaker to the heart muscle. Silicone is also used in artificial hearts (ventricular assist devices).

Selection of the suitable material

The selection of the suitable rubber material depends primarily on the intended application. Various criteria must then be taken into account, such as:

- What temperature is the molded rubber part exposed to in use?

- Does the rubber material come into contact with aggressive chemicals or medications?

- Does the rubber material potentially have direct contact with the patient?

- Is the molded rubber part implanted?

- Is there any special cleaning or sterilization?

- Over what period of time will the molded rubber part be used and stressed?

- What mechanical stress is the molded rubber part exposed to?

There are numerous different rubber materials, all of which have different strengths and weaknesses (see overview of different rubber materials). Depending on the application, the various properties must be taken into account and the appropriate material selected.

Compared to industrial applications, biocompatibility of the material used is more often required in medical technology. This is particularly the case when the medical device and especially the rubber part used are in direct contact with the patient or other substances that come into contact with humans, such as blood, medications or medical fluids.

Biocompatibility means that materials, assemblies or products have no negative influence on humans or living beings in general. Accordingly, materials that are in direct or indirect contact with the human body must not harm the user and must be free of hazardous substances and side effects.

Frequently used elastomers

Taking into account various criteria for material selection, some elastomer types have emerged in the medical sector that are used more frequently than others:


Silicone Rubber (HTV) / Liquid Silicone Rubber (LSR)

In the field of medical applications, the biocompatibility of the material is often an important requirement. When biocompatibility is required, silicone compounds are often used in the elastomer sector.

Indeed, an important advantage of silicone rubber is that it is biocompatible and thus well tolerated by humans. The biocompatibility of a silicone compound is often demonstrated by USP Class VI classifications (USP stands for United States Pharmacopeia) or by tests in accordance with the more stringent (DIN EN) ISO 10993 guideline. (DIN EN) ISO 10993 is primarily used for testing medical devices that are implanted in the human body for a long time or permanently. For shorter applications, the classification according to USP Class VI or sometimes a lower classification is sufficient. Corresponding evidence is available for many mixtures from well-known manufacturers. More information on the biocompatibility of materials can be found here.

In addition, silicone rubber offers the possibility of steam sterilization (heating in an autoclave) due to its property of being able to be used in a wide temperature range from around -80 °C to approx. 250 °C. Products made of silicone can thus be freed from living microorganisms, their permanent forms and viruses, etc. 

Silicone rubber's good electrical insulation properties are also of particular importance in the medical field.

Thanks to its high stability within the human body, silicone rubber thus provides very good protection for critical components and is also the preferred material for functional parts due to the aforementioned properties.

Silicone is used as a preferred material in medical technology. In addition to articles for medical devices (seals, membranes, bearings), components made of silicone rubber are also used as short-term (for less than 30 days in Class IIa medical devices) or long-term implants (used for 30 days or more in Class IIb medical devices), where they perform critical functions in devices such as cardiac catheters, pacemakers, ventilators, neurostimulators or defibrillators.

HTV (high temperature vulcanizing) or HCR (high consistency rubber) are types of silicone rubber whose raw material is solid. They are vulcanized at high temperatures, usually between 140 °C and 200 °C. The crosslinking is achieved either by peroxides or by addition cured reaction, in which platinum compounds are used as catalysts. 

Liquid silicone rubber (LSR) is (viscous) liquid as a raw material and consists of two components that are mixed directly before processing. Crosslinking takes place by addition reaction at temperatures similar to those of HTV grades, although crosslinking is generally much faster. Another advantage is that the purity of LSR materials is easier for the processor to ensure than with HTV mixtures.

Both silicone types can be colored.

Finished elastomer articles made of HTV silicone and LSR silicone hardly differ in their properties. Silicone rubber, for example, is resistant to various liquids such as water, (isopropyl) alcohol and some acids. It is also characterized by its excellent temperature resistance over a very wide temperature range. Silicone can be used in a temperature range from -80 °C to approx. 250 °C without losing much of its original mechanical properties.



EPDM is known for its excellent resistance to weathering, water and aging, which are not of great importance in the medical field. However, due to its overall broad property profile in terms of its mechanical properties as well as its media resistance, EPDM is used quite frequently in medical technology and is often found in medical devices.

In this case, compounds can be created that are compliant with FDA requirements (more on FDA-compliant rubber compounds can be found here).

EPDM is considered a very durable and resistant material. Rubber parts made of EPDM are therefore used, for example, in the form of seals, O-rings, diaphragms or valves in respirators, dosing systems, pumps, drug delivery devices and fluid transfer systems such as infusion systems.

EPDM is resistant to various aggressive chemicals and therefore well suited for use in the medical industry. EPDM has very good resistance to polar chemicals such as water, waste water, alkalis, alcohol and glycols. Water vapor, alkaline cleaning agents, acids and various organic as well as inorganic bases also pose no problem for EPDM.

EPDM is a good all-round material for mechanical loads. The tensile strength, tear resistance and elongation at break are average to good.

If compression set plays a major role, as in the case of seals, EPDM compounds with very low compression set can be used.

Articles made of EPDM can generally be used at temperatures between -40 °C and 130 °C. For a short time, use up to 170 °C is also possible. 


Fluororubber (FKM)

Some medical applications require the materials used to have special properties in terms of their resistance to media, since they come into contact with very aggressive chemicals, for example. In such cases, FKM is often used as the elastomer material because of its excellent resistance to a wide range of aggressive media and its outstanding behavior at high temperatures. Many people are familiar with fluororubber under the brand name Viton, under which the US chemical company DuPont (now DuPont de Nemours) markets FKM.

If aggressive substances are used in a medical application, elastomers such as silicone rubber or EPDM are out of the question in many cases. Fluororubber (FKM) is resistant to many media, such as various oils and greases, acids, glucose, oxygen and carbon dioxide. Especially when the functionality of a component such as a seal is critical for the entire device and a failure would mean serious consequences, FKM offers advantages here compared to other rubber materials.

In addition, rubber parts made of FKM are very heat-resistant. They can be used permanently at temperatures of up to 220 °C without further ado. Higher temperatures of up to 300°C are often possible for short periods (up to 70 hours). This property is of enormous importance in some medical fields.

In terms of its mechanical properties, too, FKM is a very solid material that is particularly resistant to stress. Particularly worth mentioning is its excellent compression set. Even under the influence of enormous heat, FKM seals or FKM O-rings retain their resistance and sealing effect.

In addition to FKM compounds, which are FDA-compliant and quite common, there are also compounds that meet the requirements of USP Class VI.


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