by Medical elastomers refer to rubbery polymers that are used to manufacture various medical devices and equipment. These polymers exhibit elastic properties that make them well-suited for applications involving flexibility, stretchability and resilience. Some key types of medical elastomers include silicone rubber, latex rubber, thermoplastic elastomers and hydrogels.
Silicone Rubber
Silicone rubber is one of the most commonly used Medical Elastomers. It is made by polymerizing siloxane, which gives it excellent biocompatibility. Silicone rubber does not deteriorate easily when exposed to chemicals, heat, cold or UV light. These properties make it highly durable for long-term implantable uses. Some major medical applications of silicone rubber include:
– Surgical tubing and gloves: Silicone has high oxygen and vapor permeability, making it suitable for sterile tubing and examination gloves. Its flexibility and strength provide comfort.
– Artificial hips and joints: Silicone rubber cups and sockets used in hip and knee replacements can flex naturally with the body’s movement for decades.
– Breast implants: Implants made of silicone gel or saline-filled silicone shells are used for breast reconstruction and augmentation procedures.
– Catheters: Both intravascular and urinary catheters feature silicone tubing for comfort and anti-kinking ability during insertion and use.
Latex Rubber
Natural latex extracted from rubber trees is another important medical elastomer. Though latex allergies limit its widespread use, non-allergenic synthetic latex is also available. Key medical applications of latex include:
– Examination and surgical gloves: Latex examination gloves provide a strong barrier with proper tactile sensitivity. Sterilizable latex gloves are commonly used in surgery.
– Balloons: Latex or silicone-latex balloons are inflated and deflated many times for procedures like angioplasty, stent placement and uterine monitoring.
– Condoms: Thin latex sheaths provide reliable barrier protection against STDs during sexual activity.
– Catheters: Latex is ideal for urinary foley catheters due to its soft, flexible texture within the urinary tract.
Thermoplastic Elastomers
Thermoplastic elastomers (TPEs) are a class of materials that are processed like plastics but have rubber-like qualities when flexible. Common medical-grade TPEs include styrenic block copolymers, polyurethanes and elastomeric alloys. They offer benefits like:
– Improved extrudability and moldability compared to rubbers. This allows for precisely engineered complex parts.
– Enhanced mechanical strength over pure rubbers. TPE components maintain shape and durability through multiple uses.
– Wider range of physical properties by varying hard and soft segment mixtures in the polymer.
Major medical uses of TPEs include Stopcocks, IV fluid system components, respiratory therapy equipment, wound care devices and prosthetics.
Hydrogels
Hydrogels are three-dimensional polymer networks capable of absorbing large amounts of water. When water is absorbed, they become soft and rubbery. Some commonly used medical hydrogels and their applications are:
– Contact lenses: Hydrogels like hydroxyethyl methacrylate (HEMA) are used in soft contact lenses for their high oxygen permeability and comfort.
– Tissue engineering: Hydrogels resembling natural tissue are being developed as scaffolds to promote tissue regeneration.
– Wound dressings: Hydrogel dressings help maintain a moist wound healing environment and protect from infection.
– Drug delivery: Hydrogels are beneficial carriers for localized and sustained release of medicines into the body.
Sterilization of Medical Elastomers
No medical device can be used without first sterilizing it to eliminate microbes. Common sterilization techniques used for medical elastomers include:
– Heat sterilization: Vulcanized rubbers can withstand high temperatures of steam sterilization in autoclaves up to 135°C.
– Gamma radiation: High-energy radiation is commonly used for silicone parts and cross-links TPEs without damaging properties.
– Ethylene oxide (EtO) gas: Widely applied to thermosets and thermoplastics, EtO penetrates packaging and sterilizes in ambient conditions.
– Dry heat sterilization: An alternative for thermally-sensitive devices up to 180°C in hot air ovens.
Proper material selection and packaging ensures elastomers maintain functionality after sterilization before use. Ongoing quality controls guard against contamination.
Medical Regulations for Elastomers
With increased usage, stringent regulations ensure biocompatibility, functionality and patient safety of all medical elastomers. Compliance with standards issued by the U.S. FDA, ISO and other national regulatory bodies is mandatory. Key aspects addressed are:
– Cytotoxicity testing as per ISO 10993-5 to prevent cell damage.
