Sterilization for Medical TPE

Ethylene oxide, gamma or superheated steam?

The vast majority of medical products are supplied in a sterile state. This applies both for single-use medical items sterilized once – such as respiratory tubes, connectors, syringes etc. – and for device components and instruments which are reused for cost reasons.​

As the packaging for sterile medical products is also exposed to numerous potential risks on its way to the patient – during the production process in the factory, the packaging process, and transport – it is necessary in the development of new products in the area of medical technology to take consideration of the aspects of packaging, sterilization, and transport right from the start in an effort to eliminate any possible hazards in terms of sterility. This also applies for the material used.

Sterilization methods

Sterilization can take the form of a physical (thermal, radiation) or chemical process. The following processes have proven to be the most popular: Superheated steam, Radiation sterilization, Ethylene oxide.


Sterilization with superheated steam is the standard method in most laboratories and hospitals and occurs at 121 °C or 134 °C and an overpressure of up to three bar in the autoclave. When the steam condenses on the sterilization material, energy is released which is harmful to the microorganisms. This method is only suitable for materials which are stable in terms of temperature and hydrolysis. ​

ACTEGA offers a TPE formulation in the form of PROVAMED® 6145 TL, for example, which has been optimized with regard to its temperature resistance. Following autoclaving at 121 °C (15 min.), no mechanical changes could be detected. A comparison of the mechanical values of an unsterilized specimen with those of a sterilized specimen (at 121 °C and for 15 min.) shows that there are only minimal changes which do not have any impact on the final application.


In the case of ionizing radiation, a distinction must be made between natural forms of radiation (alpha, beta, and gamma rays) and those which are generated artificially (electron beams, e-beam). The electrons are generated in an accelerator. Using a so-called scanhorn, the electron beam is then fanned out as a type of “electron shower” under which the products pass through on a transport system. The actual sterilization process only takes a few seconds and is less energy-intensive than gamma radiation.​

High-energy, ionizing gamma radiation deactivates microorganisms. When this low-temperature method is applied, the minimum radiation dose must not be exceeded. The materials are sterilized with 25 kGy and 50 kGy doses and must not display any essential mechanical changes afterwards. Not all plastics are suitable for multiple sterilization using gamma rays. This method is only applied industrially and almost exclusively for single-use items.​

In the form of PROVAMED® 4085 TP, which is particularly suitable for the extrusion of medical tubes required to display transparency and buckling stability, a TPE material is available which has proven in comparative tests that neither yellowing nor any impairment of the mechanical properties occur, not even after high irradiation with 50 kGy.


Ethylene oxide sterilization is a low-temperature method which kills microorganisms even at 10 °C by forming a bond with the protein molecules and destroying them. As the sterilization time is dependent on the temperature – the higher the temperature, the shorter the sterilization time – a temperature range of 37 °C to 60 °C is usually applied. Many plastics display good chemical resistance to ethylene oxide. In combination with the low process temperature, this method is suitable for a wide variety of thermoplastic materials.​

ACTEGA’s PROVAMED® D1341 TP TPE formulation has proven to be particularly suitable in this regard: ultra-transparent, solvent-bondable, and without any impairment of the mechanical properties during the comparative test.​

Each of these methods can prevent biological contamination. But they also display both advantages and disadvantages as well as considerable impacts on the material used. In order to avoid negative impacts, the material formulae need to be compiled very carefully with stabilizers and other supporting ingredients – as is the case with the PROVAMED® portfolio. Comprehensive tests on the various variants during which gamma irradiation, autoclaving, and gassing with ethylene oxide are compared, show that these materials are resistant to signs of wear such as swift ageing, brittleness, discoloration, or changes in mechanical properties.

Comparison of sterilization processes

EtO sterilization has recently become a topic of discussion, whereby Eucomed, the umbrella organization of companies in the medical device industry, has established that “When the existing regulations and protective measures for the various products and materials are complied with, EtO sterilization is an indispensable, reliable, and validated method of sterilization of medical products.”​

As EtO sterilization is not suitable for materials and products with complex geometries which are sensitive to temperature or moisture, sterilization with beta or gamma rays is recommended here which radiate through the material, thereby reliably destroying pathogenic germs, mold, and spores. For both types of sterilization, the germ load of the products to be sterilized is determined on the basis of the DIN EN ISO 11737 standard. Radiation sterilization is suitable for a wide range of medical products. Here, too, suitability of the materials should be examined within the framework of validation. Unlike EtO sterilization, radiation sterilization only requires physical performance evaluation (dose mapping) once per product as part of the validation process – this saves time and money. This environmentally-friendly and residue-free method enables use of the products immediately after approval. Unlike EtO sterilization, no time-intensive desorption phase is required.

Do you have any questions? Contact us and we will be happy to advise you on your individual requirements.

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