Medical elastomers are polymers that are elastic in nature and find extensive applications in the healthcare sector. The Elastic and flexible properties of these materials enable their use in various medical devices and equipment. Some key medical elastomers and their properties are discussed below along with their roles.
Silicone Elastomers
Silicone elastomers are one of the most widely used Medical Elastomers due to their excellent biocompatibility and stability. They do not elicit an inflammatory response in the human body. Silicone elastomers have outstanding flexibility over a wide range of temperatures. They are also stable when exposed to radiation, chemicals, and temperatures ranging from -80°C to 300°C.
Due to their temperature stability and flexibility properties, silicone elastomers are used to make sealing components, tubing, catheters, implants etc. They are also used to make gloves, breast implants and other prosthetics due to their skin-feel properties. Silicone elastomers demonstrate very low levels of absorption, adsorption and extractability making them highly suitable for use in medical devices that come in contact with living tissue or bodily fluids.
Thermoplastic Elastomers
Thermoplastic elastomers (TPEs) are elastic in nature but can be reshaped upon applying heat, unlike vulcanized rubber. Examples of medical-grade TPEs include styrenic block copolymers (SBCs), olefinic elastomers and polyurethanes. TPEs have properties between plastics and vulcanized rubbers – they are flexible and elastic at room temperature but can be molded easily on application of heat.
TPEs find applications in pouches and stoppers where easy formability and sealability are important. They are also used to make respiratory components, face masks, catheter components etc. due to their flexibility and affordability compared to other elastomers. The thermoplastic property enables recycling of these materials. TPE components can be sterilized using heat, gamma radiation or ethylene oxide gas.
Thermoset Elastomers
Thermoset elastomers include silicone rubber, ethylene propylene diene monomer (EPDM) rubber, chlorosulfonated polyethylene (CSM), polychloroprene etc. Unlike TPEs, thermoset elastomers do not soften on application of heat once cured or crosslinked. This makes them suitable for applications requiring high heat or chemical resistance.
Silicone rubber is used to make tubing, medical device components, gaskets, respirators due to its biocompatibility and heat stability. EPDM is used in stoppers and tubing caps due to its resistance to oil, chemicals and weathering. CSM is used in bags and hoses for its oil and weather resistance. Polychloroprene shows resistance to cut growth, chemicals and impact making it suitable for protective clothing such as masks, gloves etc.
Key Properties and Testing of Medical Elastomers
Some key properties evaluated for medical elastomers include biocompatibility, flexibility, tensile strength, compression set, toxicity etc. Methods like cytotoxicity testing, implantation studies, and ISO 10993 biological evaluation are followed to ensure biocompatibility. Flexibility is tested using durometer, tensile strength using universal testing machines and compression set by compressing samples at elevated temperatures.
Extractable and adhesive properties are also crucial and evaluated by immersing samples in solvents like water, ethanol etc. and determining the amount extracted. Thermal properties like glass transition temperature, melting point, coefficient of thermal expansion etc. are analyzed using techniques such as differential scanning calorimetry and thermogravimetric analysis to verify suitability at specific temperatures. Sterilization capability by steam, radiation or ethylene oxide is another important test conducted on medical elastomers.
Future directions and conclusions
Research is ongoing to develop elastomers with enhanced mechanical and thermal properties for more challenging medical applications. Development of self-lubricating and antimicrobial elastomers could further expand their use. Biodegradable elastomers are also gaining interest. Blending with nanofillers and development of new crosslinking chemistries continues to enhance elastomer characteristics. Strict quality control and standardized testing help ensure the safety of elastomers used in medical devices and implants. Overall, medical-grade elastomers will likely remain invaluable materials in the healthcare industry owing to their flexible and durable properties.
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