The self-sealing capability of a septum after multiple punctures is important in many medical applications. In hospitals and other medical institutions, it is common for medical vials that store fluid to be accessed multiple times by a syringe or needle. The medical vials need to be leak free after piercing, which means the septa on the vial caps have to maintain their sealability even after several punctures in order to prevent contamination and leakage.
Requirements for elastomeric self-sealing septa for injections
The United States Pharmacopeia (USP) has established guidelines and test methods that elastomeric closures must pass in order to be qualified as self-sealing. The test method is USP <381> – Elastomeric Closures for Injections.
Self-sealing septa (aka resealable septa) must exhibit the ability to reseal themselves after being punctured several times. These elastomeric materials need to be FDA white listed and USP Class VI approved, and have passed the USP <381> test method – Elastomeric Closures for Injections. The USP <381> identifies elastomeric closures as
“[products that] are made of materials obtained by vulcanization (cross-linking) polymerization, polyaddition, or polycondensation of macromolecular organic substances (elastomers). […] Such closures are typically used as part of a vial, bottle, or pre-fill syringe package system.”
For the testing purpose, the needle used to puncture the septa is a 21 gauge needle. The USP <381> test method provides guidelines for testing the functionality of elastomeric septa in terms of penetrability, fragmentation, and self-sealing capacity. The singular form of septa is septum, which represents the seal used at the top of a vial cap, a bottle cap or a fluid container.
Penetrability testing measures the amount of force required to puncture the septum with a needle. To pass the USP test method, the force for piercing cannot exceed 10 newtons (N) for each closure. This test ensures the septa will be easily penetrable by lab technicians or automated equipment.
Fragmentation testing gauges the likelihood of the septum to break into small particles as a result of being penetrated. USP <381> requires that no more than five fragments are visible after four injections. Eliminating fragmentation reduces the risk of sample contamination and leakage.
Self-sealing capacity (aka resealability) testing measures a septum’s ability to reseal itself after being punctured by a needle. The USP <381> test requires a septum to be punctured ten times without sample leakage. Parker O-Ring Divisions new septa materials are ideally suited for multiple dose or multiple sample containers.
Based on the test results, Parker's innovative extruded septa made from a silicone S7577 and a thermoplastic elastomer (TPE) JA571 are qualified as self-sealing septa. These septa are easily penetrable by medical needles, highly resistant to coring or fragmentation, and resealable after several punctures. These seals reseal themselves after multiple punctures, ensuring leak free vials and eliminating concerns about sample contamination.