Sterilization
There are several methods of sterilization commonly used in the medical field, including autoclaving, Ethylene Oxide (EtO), Hydrogen Peroxide, Gamma, and Electron Beam (E-beam). Each has a different effect on the materials used in the development of a custom medical device, therefore, determining the type of sterilization that the device will be subjected to is a critical design issue.
Since Gamma sterilization is being used more frequently due to the reduced, post-sterile release cycle time, the product development team at Teleflex Medical OEM has developed a table that contains many common materials and the effects that can be expected when the material is exposed to Gamma sterilization.
| Material | Stability | Comments |
|---|---|---|
| Acrylonitrile/Butadiene/Styrene (ABS) | Excellent | |
| Aromatic Polyesters (PET, PETG) | Excellent | No discoloration |
| Cellulosics | Fair | Esters better than cellulose acetate. |
| - Esters and Ethers | Fair | |
| - Cellulose Acetate | Fair | |
| Fluoropolymers | Poor | TFE and PCTFE are significantly damaged at low doses. |
| - Tetrafluoroethylene (TFE) | Poor | |
| - Polyvinyl fluoride | Good | Tends to cross link. |
| - Polyvinylidene fluoride | Good | Tends to cross link. |
| - Ethylene-Tetrafluoroethylene (ETFE) | Good | Tends to cross link. |
| - Fluorinated ethylene propylene (FEP) | Fair | OK for some applications. |
| Polyacetals (Deirin, Celcon) | Poor | Irradiation causes severe embrittlement, discoloration, and cracking over time. |
| Polyacrylics | Fair | Yellow discoloration tends to fade with time. Stabilized and tinted materials available. |
| - Polymethylmethacrylate | Fair | |
| - Polyacrylonitrile | Fair | |
| - Polyacrylate | Fair | |
| - Polyhydroxacrylate | Fair | |
| - Polycyanoacrylate | Fair | |
| Polyallomers | Good | Copolymer of polyethylene and polypropylene reduces oxidation embrittlement of polypropylene |
| Polyamides (Nylons) | ||
| - Alphatic | Good | Slight discoloration possible. Tends to cross link increasing tensile strength. |
| - Aromatic | Excellent | |
| Polycarbonate | Excellent | Yellows slightly. Mechanical properties not much affected. Tints stabilizers available. |
| Polyethylene | Excellent | Cross links, tensile strength increases, and modulus of elasticity decreases. |
| Poly (ethylene-acrylate) | Good | |
| Polyimides | Excellent | Doses exceeding 1000 Mrads are OK. |
| Polymethylpentene | Good | |
| Polyphenylene Sulfide | Excellent | Doses exceeding 5000 Mrads are OK. |
| Polypropylene | Good-poor | Stabilization required to prevent embrittlement. Exercise caution because effects may increase with time – months after irradiation. |
| Polystyrene | Excellent | Slight yellow discoloration possible. |
| Polysulfone | Excellent | Natural material is yellow. |
| Polyvinyl formal | Good | Less stable than PVC. |
| Polyvinylbutyral | Good | Less stable than PVC. |
| Polyvinylchloride (PVC) | Good | Can discolor but stabilizers available to prevent yellowing. |
| Polyvinylidene Chloride | Good | Less stable than PVC. |
| Styrene/Acrylonitrile (SAN) | Excellent | Less stable than styrene alone. |
| Allyl digylcol carbonate (polyester) | Excellent | Maintains excellent optical properties. |
| Epoxies | Excellent | Aromatic curing agents are recommended. |
| Phenolics | Excellent | Mineral fillers increase stability |
| Polyesters | Excellent | The use of mineral fillers or glass fibers further increases stability. |
| Polyurethanes | Excellent | Discoloration is normal. |
| Material | Stability | Comments |
|---|---|---|
| Butyl | Fair | |
| Ethylene-Polyproylene Oiene | Excellent | |
| Fluoro | Good | |
| Natural | Excellent | |
| Nitrile | Fair | Discoloration is normal. |
| Polyacrylic | Good | |
| Polychloroprene (Neoprene) | Good | Some discoloration. Aaromatic plasticizers improve stability. |
| Silicones | Good | Phenyl substituted materials are more stable than methyl silicones. |
| Styrene-Butadiene | Excellent | |
| Urethane | Excellent |
- Excellent: Doses of more than 100 Mrads may not cause significant damage.
- Good: Doses in range of 20 to 100 Mrads may cause significant damage.
- Fair: Doses in range of 5 to 20 Mrads may cause significant damage.
- Poor: Significant damage may occur at doses of 2 Mrads or less.
"Damage" refers to significant changes that affect the physical properties; other effects like discoloration may occur at lower doses.
*Please note: Information is for reference only. The suitability of a material for use in your project must be determined as part of the product development process.