Owing to their great flexibility, high thermal and media resistance, major advantages in terms of processing and recycling, the demanding and sophisticated recipes of thermoplastic elastomers (TPE) now represent the perfect alternative to vulcanized rubber, PVC and silicone in practically any area of application. TPE can be melted, extruded and injection-molded, and offer a range of technical processing advantages. Particularly in sensitive and highly-regulated markets such as food packaging, cosmetics, pharmaceuticals and medical technology where minimization of the migration potential, bio-compatibility, consumer and patient protection, hygiene and sterilizability are required, the use of TPE has proved indispensable.
TPE materials are therefore very popular in manufacturing for medical technology and in clinical applications. Unlike the silicone materials frequently used in the past, TPE compounds reveal significant advantages as they are both lighter and stronger as well as being opaque, among other things. At the same time, it is important that there are no interactions or mass transfers between the material to be processed and the actual object. Both bio-compatibility and low-migration properties are therefore of the essence.
These are also key prerequisites for medical tubes where interactions between the tube material and pharmaceutical or endogenous substances need to be avoided at all cost. What's more, a high degree of transparency is required for such applications to ensure visual flow control. Resistance to buckling and germs as well as the possibility to integrate radiopaque stripes in the tube system are only some of the manifold requirements prevailing in this highly-sensitive area.
Another equally demanding area is represented by the medical environment which deploys drain tubes literally inserted under patients' skin. On the other hand, this necessitates bio-compatibility, suitability in accordance with USP VI/ISO 10993 and minimum migration. In developing the TPE compounds for the ProvaMed® portfolio offered by Actega DS, particular attention was therefore paid to ensuring the lowest possible migration potential, bio-compatibility, protection from irritations of the mucous membranes, freedom of PVC, phthalates, silicone and latex, as well as the possibility of sterilizing/autoclaving the material as required for practically all medical applications.
Sterilization is in fact a keyword within the medical environment. The aim is to protect both personnel and patients from germs, bacteria and viruses. This in turn requires a medical product to be sterile. Under the aspects of economical and technical feasibility, methods have evolved involving gassing with ethylene oxide, radiation with gamma or beta rays, and hot steam processing in an autoclave. Each of these methods can prevent biological contamination but they also have significant effects on the material used. In the case of high-energy gamma radiation, for example, these can involve rapid ageing, brittleness, discoloration and altered mechanical properties while the high temperatures in the autoclave can cause the plastic to shrink, deform or even melt. In order to avoid these negative influences, the material recipes need to be compiled very carefully using stabilizing agents and other supporting ingredients such as displayed by the ProvaMed® portfolio.
Extensive tests on the various variants comparing gamma radiation, autoclaving and gassing with ethylene oxide display the resistance offered by these materials to the wear features referred to above. Even after radiation with 50 kGy, tensile strength remains practically unchanged. The high temperatures prevailing in the autoclave can even have a positive effect on the annealing and solidification processes associated with some polymers containing TPE compounds which can increase both tensile strength and elongation. Similar effects could also be established by gassing with ethylene oxide: these TPE compounds are therefore suitable for all medical applications demanding sterilization of the finished product.
Thanks to their great flexibility and versatility, TPE compounds have succeeded in asserting themselves on the expanding medical market in particular where further material developments and innovations are to be anticipated.