Silicone rubber medical applications

Rimplast (Petrarch Systems) Blend PA Silicone rubber Medical applications... 

RIMPLAST (Evonik)i Blends Various TPEs Silicone Rubbers Medical applications... 

Hron P. Hydrophilisation of silicone rubber for medical applications. Polym Int, 2003, 52, 1531-1539. Tcholakian RK and Raad. Durability of anti-infective effect of long term silicone sheath catheters impregnated with antimicrobial agents. Antimicrob Agents Chemother, 2001, 45(7), 1990-1993. 

Particle size of the silica and tight control of its size distribution decides the ability of the compounded silicone rubber to be optically clear, even at quite high levels of addition. This feature can be used to advantage in a number of medical applications such as intraocular and contact lenses, medical tubing, flexible lights and a number of other industrial applications where sustained clarity of transparency is important. 

Processing requirements for thermoset composites, with specific examples of silicones, were recently reported.514 Composites based on the low molecular weight polysiloxanes for medical applications have been reviewed (in Russian).515 Silicone rubber/hydrogel composites have been evaluated for medical applications.516... 

Finally, silicone rubbers are superior to organic rubbers because they have no harmful effect on living organisms this gives them a whole range of applications in the production of medical materials and devices. 

The Raman microprobe has been used to detect foreign bodies in various tissues (38). Figure 3-9 shows spectra of lymph node tissue of 5 pm size, which was obtained by biopsy from a patient. The foreign body was identified as a particle of silicon rubber (dimethyl siloxane). For more biological and medical applications, see Section 6.2.4. 

Silicone rubber tubes are mainly utilized in medical and food technology e.g. as transfusion tubes, catheters and tubes for drinks. Silicone cables are widely utilized in applications for which thermal stability, weathering resistance and chemical resistance are required e.g. baking ovens, hot lamps and electrical connections for electrical motors and transformers. 

Some of the applications Include contact lenses, medical tubing and protective gas masks. The silicone rubber for these applications is optically clear because the silicone polymer and the reinforcing silica used to prepare the rubber are isorefractive at a specified temperature, usually about 25 C. The polymers which have been used are copolymers with sufficient phenyl substitution to raise the refractive index, from 1.4023 (for PDMS) to approximately 1.43 which is the refractive index of tri methyl si lyl treated fumed silica (e.g., Cabosll S-17). Such copolymers are prepared by copolymerizing (Me2S10)x and (PhMeSiO) or (Ph2S10)x using equilibrium conditions. 

PU and silicone rubber are biocompatible materials which are commonly used in a variety of medical applications [53], e.g., as a raw material for central venous catheters and tracheotomy tubes. Although these materials are biocompatible, the side effects which occur during clinical use include inflammation, infection and biofilm formation and growth. This in turn initiates the degradation of the material, e.g., previous studies have proven that the degradation of PU catheters is caused by either oxidation or hydrolysis of the material [54]. The degradation of silicone rubber is a hydrolysis phenomenon [55], which could be catalysed by an acidic environment. 

A variety of polymers are used in engineering and medical applications which have relatively little impact on the environment. These are mainly high performance and relatively expensive polymers such as the silicones in rubbers, the specialised polyamides referred to above in gear wheels, polycarbonates (in office equipment), chlorinated and sulfonated rubbers, fluorinated polymers such as poly tetrafluoroethylene) Teflon ) in metal coating and the polyimides which, owing to their ladder structure, are extremely stable in high temperature apphcations. Since these polymers are high-cost durable materials, they rarely appear in the waste stream. 

Siloxane polymers (better known in the commercial market as silicones) have widespread applications, a few of which are personal care products, greases, sealants, varnishes, waterproofing materials, synthetic rubbers and gas-permeable membranes such as those used in soft contact lenses. Medical applications are increasing in importance, although the use of silicone breast implants is a controversial issue because of claims of the migration of low molecular weight siloxanes from the implant into the surrounding body tissue. 

Vertrel XSi Is a proprietary blend of Vertrel XF hydrofluorocarbon and hexamethyidislloxane. It is ideally suited for use in medical applications as a solvent for cleaning or depositing of silicone oil-based lubricants. It is also used as a swelling media for silicone rubber tubing. 

Silicone rubber Seals, flexible hoses for medical applications, etc. 

Uses of Silicone Rubbers. Becanse of their high cosL silicone elastomers are used only in applications where other elastomers fail. They are mainly nsed in applications requiring high heat resistance and extreme low-temperature flexibility. These elastomers are used in the electricaL electronic, aerospace, antomotive, mechanical equipment, fighting, cable, and textile indnstries. They are also nsed in pharmacentical and medical applications for components in contact with food. They are now nsed in high-temperature cooking utensils (e.g., scrapers and spatulas). 

Materials such as platinum, titanium, silicon rubber, some fluropolymers, and various polyurethanes are among the mainstays in this industry, along with a few exotic nickel-based superaJloys. The most common material found in implantable medical devices is likely 316 stainless steel. Other than improved wear resistance, there is little driving force for advancing materials in this application. 

These are typically built on a polyester base membrane (PETP, 35 pm, copper-laminated) with a polyester spacer membrane, safety chamber and front membrane. The snap disc being gold plated stainless steel. Other designs use electrical contacts made from silver, silver on carbon or carbon only. Keypads may also be made from conductive silicone rubber. Conventional computer keyboards made from ABS, polyester or other polymers, may be covered by a polymer overlay to protect it against dirt, dust, water or other substance present in a hostile environment. Polyester and PVC overlays are used in a wide variety of applications with computer and instrumentation equipment in dental and medical healthcare and other areas. Typical casing materials include PC and polychloroprene. 

In electronics transmission and distribution at medium and high voltage, automotive, medical and many other applications silicone rubber is a preferred material for various reasons its outstanding chemical resistance, heat ageing, dielectric (insulating) properties, unlimited pigmentability, flexibility in the cold and a wide spectrum of further advantageous properties make it the ideal material. In many cases, there is no alternative to silicone rubber. 

Silicone rubbers, both, peroxide and addition curing, are used in the manufacture of composite parts. Known applications focus on automotive, medical, sanitary, household, transmission and distribution (T D), electronics and food appliances. 

Silica, from natural sources, is used as a feedstock to produce very fine particle precipitated, hydrated, amorphous silica, and fumed silica, both commonly used in different ways as reinforcing fillers in rubber technology. Also, silicone rubber, vital to aerospace and medical applications, is ultimately based on silica as a raw material. Because of the abundance of silica in nature, there will never be a shortage of this raw material. 

The silicone elastomers possess a high degree of flexibility at low temperatures [to -90°C (-130°F)] and yet are stable to temperatures as high as 250°C (480°F). In addition, they are resistant to weathering and lubricating oils, which makes them particularly desirable for applications in automobile engine compartments. Biocompatibility is another of their assets, and, therefore, they are often employed in medical applications such as blood tubing. A further attractive characteristic is that some silicone rubbers vulcanize at room temperature (RTV rubbers). 

Compoimd crosslinking silicone rubbers do not form fission products during crosslinking. However, despite the high degree of complete chemical reaction, a 100% reaction cannot be achieved. This means that volatile polymer components remain behind in the finished part. For applications in the food industry or in medical areas, liquid as well as solid silicone rubber products must be tempered in accordance with regulations, for example the German BgW and in the US the FDA. 

Perhaps the most commonly used implantable material is silicone rubber. This material, if properly prepared by the manufacturer, does not cause local toxic response. Various types of epoxy polymers and polyurethane materials also have found one or more medical applications. 

Silicones have been used in medical science for a variety of prosthetic applications because of their unique properties such as biocompatibiUty, weather resistance, low chemical reactivity, oxidation resistance and low toxicity. These properties make them suitable for a variety of applications, including maxillofacial reconstruction, breast implants, cochlear implants, artificial corneas and artificial skin. Silicone rubber (SR) implants have long been used for local contour corrections, such as nasal, chin, and cheek augmentation. In addition, arthritic knees and joints are effectively replaced by SR prostheses [1 ]. 

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