Munich -- At this years international trade fair for high-tech solutions for medical technology, COMPAMED, Munich-based chemicals company Wacker will be unveiling a new liquid silicone rubber for radiation-sterilizable silicone valves used in medical devices. The product, available under the name SILPURAN 6610/40, serves in the production of biocompatible silicone valves whose slits do not close up or "heal" during radiation sterilization. The new silicone rubber allows such valves to be made without the use of additional auxiliaries. For instance, silicone valves ensure that infusion systems administer the correct dose of liquid medication. COMPAMED 2011 takes place in Düsseldorf, Germany, from November 16 to 18.

Medical equipment for administering liquid medication frequently employs valves made from silicone elastomers. These offer high dosing accuracy, are biocompatible and can be very readily sterilized on account of their resistance to heat, radiation and chemicals. However, it is not unknown for the slits of such silicone valves to close up ("heal") when radiation-sterilized, a common practice in medical technology.

Whats more, the higher the radiation dose, the more the slits close over. This can impair the dosing accuracy of the valve and may even cause it to fail completely. Consequently, valve manufacturers have so far resorted to a process auxiliary which prevents opposing slit edges from touching. The auxiliary is a liquid or particulate release coating which is applied to the edges of the slits as they are being created in the membrane.

The advent of SILPURAN 6610/40 silicone elastomer obviates the need for a release agent. This liquid silicone rubber is so durable that the valve slits will not even heal when exposed to radiation doses far in excess of those usually employed in sterilization. This non-healing effect is the outcome of a special formulation of the liquid silicone rubber and also allows the silicone valve membrane to be slit prior to post-curing. The valve slits can be created either with a suitable mold during injection molding itself or with a punching die after demolding.

Eliminating the need for a release agent makes it possible to produce silicone valves in SILPURAN 6610/40 much more quickly, cleanly and inexpensively than before. SILPURAN 6610/40 lowers the risk of contamination that is associated with release agent, such as when the valve is being made or installed in medical equipment.

Valves need to be particularly accurate when used for dosing medicines. Those made from SILPURAN 6610/40 can be sterilized with ionizing radiation prior to shipping, without suffering any loss of dosing accuracy. As a result, needle-free infusion systems and insulin pumps, along with other medical equipment that employs silicone valves, offer a high level of patient safety. There is no possibility that the equipment will fail through radiation-induced valve healing. Like all SILPURAN products, the new SILPURAN 6610/40 liquid silicone rubber is biocompatible according to selected ISO 10993 and USP Class VI tests. The two-component product is produced in white and is packaged in cleanrooms.

SILPURAN - Silicone Products for Medical Applications

Wacker has put special measures and its new Wacker CLEAN OPERATIONS production standard in place to ensure that the SILPURAN silicones will continue to meet high standards and ever-rising safety demands in the future, too. All SILPURAN silicone rubber is dispensed or packaged in cleanrooms to prevent contamination by airborne particulates. 50-micron filtering, visual inspections and, for solid silicone rubber, the use of antistatic, welded in-liners ensure the best-possible levels of purity.

SILPURAN silicones are free of organic plasticizers, are radiation-resistant, can be readily sterilized and are biocompatible according to selected ISO 10993 and USP Class VI tests. According to ISO 10993, the materials were tested regarding cytotoxicity, pyrogenicity and sensitizing properties. USP Class VI tests included the examination of acute systemic toxicity, intracutaneous toxicity, and short-term implantation.

Radiation-sterilized membrane, made from a standard silicone elastomer and from Wackers new SILPURAN 6610/40. The dosing slit in a standard silicone elastomer (left) gradually heals during irradiation with gamma radiation or E-beam unless a release agent is used. SILPURAN 6610/40 is different: This silicone elastomer is formulated so that the slit remains completely intact, without the need for a release coating.