Medical Grade Silicone

Medical grade silicones are silicones tested for biocompatibility and are appropriate to be used for medical applications. Before it can be applied medically, it must pass rigorous FDA standards. Medical grade silicone is hypoallergenic, latex-free and containing no toxins, and is also nonporous and so resists bacterial growth.

Medical grade: More technically referred to as medical-healthcare grade. they are generally grouped into four categories: non-implantable, skin contact only, short term implantable (which is typically up to 29 days), long-term implantable (which is greater than 29 days). Materials approved as Class V and VI can be considered medical grade. Most medical grade silicones are at least Class VI certified.

Usually, food grade silicone is safe to use for food storage or cooking. Medical grade is considered a step above that, meaning that it can be used in applications that touch human skin or are in contact with other human tissue.

Raw Material

Medical grade silicone rubber raw materials are mostly HTV silicone rubber types, including LSR  (liquid silicone rubber) and HCR (high consistency rubber, also known as solid silicone). Medical grade platinum-cured silicones are normally translucent or transparent  but can be supplied in custom colors such as pink or baby blue to support distinctive designs for medical devices or equipment.  Materials generally range from 10 to 90 Shore A hardness.

Medical devices manufactured from medical grade silicone use various processes such as compression molding, transfer molding, and injection molding. LSR is used in liquid injection molding in order to create implantable parts of excellent flexibility and strength. The cure time is relatively less than High Consistency Silicone Rubber (HCR), which helps to reduces production costs. HCR silicone is used in transfer molding to achieve specifications such as thin walls or complex shapes.

Medical grade liquid silicone rubber application is the most extensive and common, it is a two-component platinum cured material, where the A part contains the catalyst (platinum) and the B part contains the cross-linker. Both parts are pumped and mixed, metered into the injection unit, the vulcanized under heat and pressure in the mold (process referred to as LIM: Liquid Injection Molding). Compared to other elastomers, medical grade silicone can remain stable through temperatures ranging from –75°F to 500°F.

Feature

1. Bio-inert material in compliance with ISO 10993, USP Class VI and RoHS standards.
2. Has excellent resistance to chemical, oil, oxidation, light, UV rays & X-rays.
3. FDA biocompatibility, it means that something is compatible with human tissue. Something that is biocompatible should not create a toxic response from the human body.
4. Exhibit stability and flexibility at extreme temperatures of heat or cold.
5. Has excellent dielectric properties for use with device electronics.
6. Excellent transparency, which allows light transmittance and illumination.
7. Silicone does not encourage bacterial or fungal growth.
8. Medical-grade silicone is non-porous.
9. Platinum cured medical silicone rubbers that are fully cross linked do not produce extractables.

Applications

Typical uses of medical grade silicone:

1. Medical Device Components (such as catheters, surgical incision drains, medical electronics, syringe pistons, medical gaskets, respiratory devices, medical tubes as well as parts such as valves and medical rings)
2. Diving Equipment
3. Silicone face masks
4. Condoms
5. Silicone Menstrual Cups
6. Sex toys

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The ISO standard for medical grade materials is 10993. Some of the considerations for biocompatibility are:

1. Cytotoxicity/growth inhibition (ISO 10993-5)
2. Hemolysis (ISO 10993-4)
3. Chemical analysis/"fingerprinting" (ISO 10993-18)
4. Biological-toxicological evaluation (ISO 10993-1)

Manufacturers and suppliers of medical grade materials will often label their products as such and provide statements of certification to specific OEM material specifications, which usually contain references to relevant regulatory requirements.