Sterilization is a necessary process in the medical field to eliminate potential bacteria, viruses, and other contaminants from equipment that comes into contact with humans. Lack of or poor sterilization reduces patient safety and increases the risk of disease. Our blog explains how rubber, a widely used material in healthcare, undergoes this practice so it can be properly used to help heal and save lives.
Water and Steam Sterilization
Water reaches its boiling point and converts to steam at 212°F (100°C). To ensure its effectiveness, high-quality water must be used. Considerations regarding mineral content and pH levels are critical, given that dirty or low-quality water can result in residue on surgical instruments, making the equipment unsuitable for application. Distillation and reverse osmosis serve as the primary techniques to ensure water purity; the former eliminates minerals and contaminants to purify the water, whereas the latter filters contaminants from the water supply.
Through autoclaving, which uses high pressure and heat to eliminate microorganisms like spores, viruses, and bacteria, steam sterilization is achieved. The correct autoclave temperatures for sterilizing rubber with steam range from 121ºC (250ºF) to 123ºC (253ºF) for no more than 60 minutes, as exceeding this duration risks damaging the rubber. This process is followed by drying cycles, typically lasting 4 to 8 hours at temperatures between 105ºC (221ºF) and 110ºC (230ºF), to clear out any remaining moisture.
For optimal steam sterilization, the ideal moisture balance is 97% vapor and 3% liquid. Using superheated or excessively dry steam can degrade the rubber, causing cracks or other physical damage. Conversely, wet steam with too much water content diminishes the sterilization process and may result in wet packs, leaving residual moisture during packaging that may lead to contamination down the line.
There are many good choices for rubber to use with water and steam sterilization. Preferably, you want one that will not degrade or fail in hot temperatures; choices with high heat resistance include silicone (VMQ), ethylene propylene diene monomer (EPDM), tetrafluoroethylene/propylene (TFE/P), hydrogenated nitrile (Buna-N), and perfluoroelastomers (FFKM). All of these types will withstand the heat that comes with water and steam sterilization.
Gamma Radiation
Gamma radiation impacts polymers through two simultaneous reactions: it breaks intermolecular bonds, leading to embrittlement and a decrease in the rubber’s toughness, and it increases cross-linking, which raises the compression set (the permanent deformation retained after a compressive force is removed). Additionally, radiation can alter physical properties, such as reducing elongation and discoloring specific elastomers.
Due to the low levels of radiation used in sterilization, VMQ and peroxide-cured EPDM are used. VMQ can slightly harden but retain elasticity after gamma exposure and is commonly used for single-use or limited-use devices. EPDM experiences a minor stiffness increase but is stable under moderate radiation. Although EPDM is typically sulfur-cured, in the medical field it undergoes peroxide curing because of its chemical purity, prevention of fluid contamination, and lack of degradation during sterilization.
ETO Sterilization
Ethylene oxide (ETO) sterilization employs a low dosage of chemical gas at low temperatures ranging from 25ºC (77ºF) to 63ºC (145ºF) to effectively sterilize rubber components. This method destroys contaminants like bacteria through a process called alkylation, which prevents cell functioning of the contaminants. Afterwards, a degassing or post-sterilization aeration phase is required to ensure the gas completely exits the rubber before safe usage.
VMQ and peroxide-cured EPDM represent two ideal rubber options for ETO sterilization. For silicone rubbers, exposure to ETO gas results in minimal effects, allowing the material to maintain stability with the benefit of no major changes to its qualities, like hardness. Peroxide-cured EPDM displays a comparable capacity to withstand this sterilization method.
Need to Clean Up Your Act?
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