Seals for medicine and pharmaceuticals need to comply with various and extremely demanding tasks considering that they are used in critical components and processes such as in therapeutic, diagnostic equipment or in infusion devices.
Carefully compounded - safely combined
As a general rule, materials must correspond with the specifications of the U.S. Food and Drugs Administration as well as the USP Class VI Standards. They need to be tested for biocompatibility (ISO 10993) and physiological safety as well as guarantee the material’s compatibility with the human organism if there is direct contact between the material/product and patient.
Sterilizability as well as resistance to chemicals and media are other characteristics to be taken into consideration. By applying the corresponding level of care, PROVAMED¨ TPE are exclusively compounded from raw materials approved for medical applications and subject to strict selection criteria. This material quality means that products thus manufactured pass the decisive medical tests.
Compounds for medical syringe piston seals
A syringe - for administering medication (injections), drawing body fluids (puncture) or tissue (biopsy), infusing fluids and nutrients as well as for irrigating wounds - comprises a cylindrical cavity containing a mobile piston, a conical or cylindrical nozzle, and a seal mounted at the end of the piston.
By the way, the first syringe for administering liquid medication - so-called injectables - was developed by a Frenchman, Charles-Gabriel Pravaz, in 1841. While the disposable syringe bodies are usually made of polypropylene or cycloolefin copolymer plastic, the seals are based on rubber, caoutchouc, silicon or TPE.
A variety of demands are made of these seals:
Leakproof closure of the syringe body, support of the piston movement for precise administration, user friendliness and patient welfare, to name but a few. Apart from function, sterility and low-migration properties, the material must also meet the requirements of the EN ISO 7886 standard (for disposable syringes) establishing its gliding properties, tightness and mechanics. The connector on a catheter coupling must be capable of withstanding specified tensile forces on the one hand but must not be crimped or otherwise damaged on the other.
Apart from caoutchouc, the material of choice in the past was often silicon as it was regarded as being generally compatible. Nowadays, increasing miniaturization means that processing often represents a challenge even for experienced injection-molding experts. And there is much to be said for using TPE which are comparably easy to process as they contain a very low percentage of emitable substances, are recyclable and cost-effective, and display very good sealing and adhesion properties.
Disposable syringes are usually packed individually and sterilized. Sterilization often takes the form of gamma radiation. For many plastics, impingement by this highly-energetic radiation represents a major challenge. Embrittlement, discoloration and in some cases extreme changes in terms of mechanical properties can be the result. These effects need to be taken into consideration as early as the formulation stage for the TPE recipe. The fact that PROVAMED¨ TPE are suitable, especially for technical medical applications requiring sterilization of the end product, has been proven by numerous tests prior to and after deployment of the various sterilization methods. Even after a high dose (50kGy) of gamma radiation or autoclaving at 134 °C, hardly any changes were detected in terms of mechanical properties and the values were close to the respective original tensile strength value.
PROVAMED¨ TPE can be adapted to a wide variety of customized requirement profiles. They also offer a particularly good degree of adhesion to thermoplastics such as PE, PP, PS, ABS, PC and PA, which is also maintained even with continuous contact with media and at increased temperatures. Furthermore, they are free of PVC, phthalates, silicon and latex, which means they are also free of allergens.
Reassuring for pacifiers
The fact that TPE materials produced by ACTEGA DS are free of ingredients classified as potentially harmful is also important - and reassuring for parents - when it comes to choosing the right baby pacifier. After all, protecting babies is of utmost priority. Pacifiers serve toward satisfying the urge to suck by infants and toddlers.
Modern pacifiers essentially comprise a mouth part - the actual pacifier - and a shield or ring which prevents the mouth part from being swallowed. The ring is often based on a polypropylene and, while pacifiers were often made of latex or silicon in the past, they are increasingly manufactured from a TPE today. Using multi-component injection molding, the pacifier and ring can be manufactured in a single work step. Fabric pacifiers or sucking bags were popular from the late middle ages well into the 18th century - for feeding, pacifying, or distracting in times of famine, but also to counter itching while teething.
The modern rubber pacifier was developed in the second half of the 19th century while today’s standard palatal form was designed by the dentist Adolf Müller in 1949. Apart from pacifiers and bottle teats, special pacifiers are also used today as teat trainers in therapy for weak babies, malfunctions in mouth motor activity, and in speech therapy. ACTEGA DS offers compounded PROVAMED¨ TPE for these applications for the special requirements of baby items which are also free of PAH, thereby complying with the (EU) Directive No. 1272/2013 which specifies binding limit values for PAH. It goes without saying that they are also free of BPA as well as being thermally stable. Furthermore, they are particularly suitable for adhesive compounds with standard thermoplastics such as polyolefins and display an outstanding degree of transparency.
TPE display a special mechanical performance. Even after 200% elongation, the compounds offered in Shore hardnesses of A-40 to A-50 reveal deformation of only maximum 20 percent. Tensile strength is greater than nine at 800 percent elongation at break. The fact that the material is bite-resistant is also of major significance. By choosing TPE with a high degree of bite-resistance, the highest demands on safety are complied with. The most important boiling test indicated that even when boiled several times, mechanical values underwent changes of ± 10 percent. And finally, migration tests - using 50 percent ethanol - were also concluded extremely successfully. This is an important point as the teat attached to a drinking bottle comes into contact with milk. The major advantage over silicon which is often used in baby pacifiers lies in its more attractive price level, recyclability, and the possibility of cost-efficient processing.
We will be presenting these and other applications at the K-Fair in Düsseldorf from October 16-23, 2019 in Hall 8A, Stand F 11-3.
Please contact us for information on other applications.