Medical Grade Silicone: Grades, Certifications, and How to Select the Right Material

Not all silicone is created equal — and in medical device development, that distinction is not just technical, it is regulatory. The phrase medical grade silicone gets used loosely across supplier datasheets and procurement conversations, but it actually refers to a precisely defined category of materials that must meet specific biocompatibility standards, purity thresholds, and controlled manufacturing conditions before they can be considered safe for patient contact. Choosing the wrong grade does not simply mean a part feels different; it can mean a failed regulatory submission, a product recall, or a patient safety event.

This guide is written for engineers, product designers, and procurement teams who are specifying silicone for medical devices and need more than a generic material overview. Here, you will find a clear breakdown of how medical silicone is graded, what the major certifications actually require, how USP Class VI and ISO 10993 relate to each other, and how to match material properties to your application's specific demands. Whether you are developing a wearable health device, a surgical instrument component, or a long-term implant, understanding these distinctions early saves time, cost, and risk across the entire product lifecycle.

What Is Medical Grade Silicone?

Medical grade silicone is a high-purity, biocompatible elastomer specifically formulated and tested for use in healthcare and pharmaceutical applications. At its core, all silicone shares the same inorganic silicon-oxygen (Si-O) backbone that gives it exceptional thermal stability, chemical inertness, and flexibility across a wide temperature range. What separates medical grade silicone from general-purpose or industrial variants is not just chemistry but a combination of factors: the curing system used, the purity of the base polymer, the absence of harmful additives or byproducts, and the controlled conditions under which it is manufactured and documented.

There is no single global definition of "medical grade," but in practice, a material earns that designation when three conditions are met simultaneously. It must be platinum-cured (addition cure rather than peroxide cure), compounded from base polymers tested against a recognized biocompatibility standard such as FDA, USP, or ISO 10993, and produced under controlled conditions — typically an ISO 14644-1 Class 8 cleanroom or stricter. Any material that misses one of these criteria cannot be genuinely called medical grade regardless of how it is marketed. Medical grade silicone is valued for its non-toxic, hypoallergenic, and durable properties — safe for contact with human tissue, fluids, and organs.

The Three Grades of Medical Silicone

Medical grade silicones are generally grouped into three categories: non-implantable, short-term implantable, and long-term implantable. These distinctions are not arbitrary marketing tiers — they reflect fundamentally different levels of testing, biocompatibility data, and regulatory scrutiny. Understanding where your device falls within this framework is the first step in any compliant material selection process.

Non-Implantable Grade covers applications where silicone contacts the skin or external body surfaces but does not enter the body. Non-implantable grade LSR can come into contact with the skin, but not the inside of the body. This category includes wearable device housings, respiratory masks, wound dressings, and external medical equipment seals and gaskets. The biocompatibility requirements at this level are meaningful but less extensive than for implantable grades.

Short-Term Implantable Grade applies to devices or components that will be inside the body for a defined, limited period. Short-term implantable silicone is used for up to 29 days or less, covering applications such as suture sleeves, connectors, and manifolds. Materials in this category must pass a broader battery of biocompatibility tests to confirm they do not cause acute tissue reactions or systemic toxicity during their service window.

Long-Term Implantable Grade carries the most stringent requirements of all. Long-term implantable silicone is typically used for 30 days or more, spanning applications such as neurostimulators, heart valves, and pacemakers.For long-term implantable devices, the FDA requires that silicone be tested and supported with biological, physical, and chemical data to be considered for use in the human body for more than 29 days.Over 50% of implantable medical devices contain silicone, which reflects both the material's exceptional biocompatibility record and the breadth of long-term implantable applications it enables.

Key Certifications: USP Class VI, ISO 10993, and FDA

Three regulatory frameworks dominate medical silicone specification: USP Class VI, ISO 10993, and FDA 21 CFR 177.2600. Each addresses a different aspect of material safety, and understanding how they intersect — rather than treating them as interchangeable — is essential for building a credible compliance story for your device.

USP Class VI

USP Class VI is a strict biocompatibility standard that confirms materials are safe for contact with the human body. Materials must pass three in vivo tests for toxicity, irritation, and long-term tissue response to be considered compliant.The United States Pharmacopeia (USP), an independent, nonprofit organization, formulates these standards, which inform decision-making at the FDA. USP Class VI is a material-level certification — it evaluates the raw compound in isolation, not the finished device. It is a narrower, faster, and more cost-effective biocompatibility standard than ISO 10993, which makes it a logical first qualification step in many development programs. Most USP Class VI-compliant silicones and fluorosilicones tolerate autoclave, gamma radiation, and ethylene oxide sterilization without degrading or leaching contaminants.

ISO 10993

ISO 10993 silicones meet stricter biocompatibility requirements than USP Class VI silicones. ISO 10993 uses different testing protocols, and the time of exposure can be limited, prolonged, or permanent — so before choosing an ISO 10993 silicone, it is important to determine which protocol applies. Where USP Class VI is a pass/fail material-level test, ISO 10993 is a risk-based framework applied at the medical device level, with testing that varies based on device use and contact duration.FDA's biocompatibility endpoint table for long-term and permanent implants includes genotoxicity, chronic toxicity, carcinogenicity, and hemocompatibility — none of which USP Class VI addresses. For European market access, ISO 10993 is the decisive standard, and many manufacturers of biocompatible silicones have both tests performed to ensure global market acceptance.

FDA 21 CFR 177.2600

In the United States, the FDA maintains FDA CFR Part 177.2600, a section that technically applies to food contact substances rather than medical materials, but it provides a foundation for material selection in the medical and pharmaceutical industries.Many silicone suppliers market their products as FDA approved or FDA compliant, meaning the material is made of ingredients listed in CFR 21, Part 177.2600, and will not release harmful substances under normal conditions of use. Engineers should understand, however, that selecting constituent materials that are FDA approved will not ensure that the full medical device receives FDA clearance — device-level approval follows a separate process determined by device classification and intended use.

Certified vs. Compliant: Why the Distinction Matters

One of the most important distinctions in medical silicone procurement is the difference between a material that is certified to a standard versus one that is merely compliant. Certified USP Class VI silicones have been independently tested for system toxicity, intracutaneous reactivity, and implantation. Compliant materials may pass the same tests, but they lack independent testing verification. In a regulated product development environment, that verification is not optional — it is the documentation that supports your regulatory submission. The same logic extends to ISO 10993: a supplier can claim compliance, but without a formal test report from an accredited laboratory, that claim cannot be used in a 510(k) or CE MDR submission. Verifying documentation depth before committing to a material supplier is always worth doing early in the design process.

It is also worth noting that USP Class VI and ISO 10993 do not say the same thing. USP Class VI is tested on the material; ISO 10993 assesses the end product in its actual use form. So "our material is USP Class VI" is a statement about the raw material, not a certificate for what you make with it. Understanding this distinction prevents teams from treating a material certification as a shortcut for device-level compliance.

Why Platinum Curing Is the Standard for Medical Applications

Medical grade silicone is almost exclusively platinum-cured, and this is by design. Platinum curing, also known as addition curing, uses a platinum-based catalyst to initiate crosslinking without releasing any volatile byproducts or residues. This clean reaction is what makes the resulting material suitable for patient-contact and implantable applications, where even trace amounts of curing byproducts could trigger biological reactions. Cured using a platinum catalyst in an addition-cure reaction that leaves no cure byproducts, platinum-cured silicone is cleaner, more inert, and typically clearer — favored for medical, pharmaceutical, food, and beverage applications where purity, low extractables, and biocompatibility matter.

Peroxide-cured silicone is widely used in industrial and some commercial applications, but it is not appropriate for most medical uses because the organic peroxide catalysts decompose during curing and can leave residual byproducts in the material. These residues require post-baking to remove and may still present extractable concerns in sensitive applications. For medical silicone, purity, crosslinking system, and the additives used are decisive — two-component, room-temperature vulcanizing silicones with platinum catalyst cure without the release of byproducts and achieve high purity levels. When evaluating any silicone supplier for a medical application, confirming the curing system is one of the first qualification checkpoints.

How to Select the Right Medical Grade Silicone

Selecting a medical grade silicone is not simply a matter of ordering the highest-specification material available. Over-specifying wastes budget and may complicate supply chain management, while under-specifying creates compliance gaps that surface late and expensively. A structured approach to selection considers four primary variables: contact type and duration, mechanical properties including durometer, sterilization compatibility, and the target market's regulatory pathway.

Contact Type and Duration

The applicable standard depends on contact type and contact duration, not on the silicone itself. This is the fundamental starting point. A silicone component used in a short-term wearable sensor has fundamentally different requirements than a catheter lumen or a pacemaker lead coating. Medical-grade LSR falls under three categories — limited exposure, prolonged exposure, and permanent contact — and the limited exposure category covers devices in contact with skin or mucosal surfaces with a service life of 24 hours or less. Mapping your device's contact scenario to these categories determines the minimum certification level required and, consequently, the testing package needed to support regulatory submission.

Durometer and Mechanical Properties

Durometer measures a silicone material's resistance to indentation on the Shore A scale, and it is one of the most practically important parameters in part design. Silicone durometer, grade, and formulation choices determine whether a part feels right, seals reliably, and survives its environment. For medical applications, durometer selection is particularly critical because it directly affects patient comfort, sealing performance, and the part's ability to conform to body contours. Softer durometers improve patient comfort and reduce skin pressure, and they adapt better to body contours.

As a practical reference, surgical drainage tubes typically require lower durometer values between 30 and 40 Shore A to minimize tissue trauma while maintaining adequate structural integrity for fluid transfer.A silicone prosthetic limb liner or implant may use a very soft silicone of around Shore A 10 to 15 so it can mimic the feel of human tissue and avoid causing irritation. At the other end, firmer formulations in the 60 to 80 Shore A range are appropriate for valve seats, mechanical seals, and components that must resist compression set over time. Choose the durometer for how the part has to seal, flex, or wear — not for how it should feel in your hand — and always confirm the scale (almost always Shore A) plus a tolerance, typically ±5 Shore A per ASTM D2240.

Sterilization Compatibility

Medical silicone components must survive repeated sterilization cycles without degrading, leaching, or losing dimensional stability. The three most common methods used in medical device manufacturing are autoclaving (steam sterilization), gamma irradiation, and ethylene oxide (EtO) exposure. Platinum-cured medical grade silicones are broadly compatible with all three, but the specific formulation and any additives present can affect performance under each method. EtO sterilization, in particular, requires confirmation that the material does not retain residual ethylene oxide above safe thresholds, since EtO is a known carcinogen. Reviewing sterilization compatibility data from the material supplier before finalizing formulation selection prevents costly surprises during device validation.

Target Market and Regulatory Pathway

The certifications required for your silicone material are partly determined by where your device will be sold. For the European market, ISO 10993 is decisive, while US customers and the FDA often additionally require USP Class VI. A device intended for global distribution typically needs to satisfy both frameworks. Many medical programs use USP Class VI to qualify materials early, then apply ISO 10993 testing at the device level for regulatory submissions. Understanding your regulatory pathway before selecting a material supplier ensures that the documentation package you receive will actually support the submissions you need to make. Confirming whether the supplier holds the testing data directly, or whether you as the device manufacturer need to commission independent testing, is a key procurement question.

Manufacturing Considerations for Medical Silicone Parts

Even a perfectly specified medical grade silicone compound can produce a non-compliant part if it is processed incorrectly. The material itself is only one part of the compliance equation — manufacturing environment, tooling precision, and post-processing steps all contribute to whether the finished part meets regulatory requirements. Manufacturers producing medical grade silicone follow strict quality control procedures that typically include carefully monitored raw material sourcing, laboratory testing, documentation reviews, repeatability validation, and traceability that covers every stage of production.

For components manufactured using Liquid Silicone Rubber (LSR) molding, the production process offers inherent cleanliness advantages. LSR can be used for molding high-precision components with thin walls and tight tolerances, and it is easy to mold at lower pressures — since it is a closed system, it is a clean manufacturing process that avoids issues with outside contaminants. LSR injection molding is the preferred process for high-volume, precision medical silicone parts because it delivers consistent material properties across large production runs. LSR can be processed in a liquid injection molding process where the liquid raw material is mixed from two separate components in a ratio of 1:1 and injected via a cold-runner system into a hot mold — curing takes place within seconds, offering fast cycling and the production of large quantities.

For lower volumes, early-stage validation builds, or complex geometry prototypes, silicone molding and compression molding offer practical alternatives. Vacuum casting is also used for functional silicone prototypes before committing to production tooling, and 3D printing technologies now support certain silicone-like materials for early-stage design validation. Each process carries its own design considerations, tolerances, and material compatibility requirements — so process selection and material selection should be developed together rather than sequentially.

Post-processing steps also play a role in final part compliance. Post-curing — heating molded silicone parts in an oven after demolding — removes residual volatile compounds and completes crosslinking, which is particularly important for platinum-cured materials used in contact with sensitive tissue. Deflashing removes thin material webs at parting lines, and inspection protocols verify dimensional accuracy against the part drawing. For implantable-grade components, full traceability from raw material lot to finished part is a non-negotiable documentation requirement.

Working with NICE Rapid on Medical Silicone Components

NICE Rapid supports product teams through every stage of the medical device development lifecycle, from first-article prototypes to validated volume production. Our silicone manufacturing capabilities span LSR molding, silicone molding, and compression molding, supported by a full suite of complementary processes including plastic injection molding, CNC machining, and vacuum casting for prototype development. Whether your project requires a small batch of functional prototypes or a transition to high volume manufacturing, NICE Rapid provides engineering-driven manufacturing support at every scale.

For medical device teams, working with a single, ISO-certified manufacturing partner from early prototyping through low volume and mid volume production reduces the risk of process changes disrupting material qualification or device validation. Our team works closely with engineers to align material selection, tooling design, and process parameters from the start — so the path from CAD file to compliant finished part is direct, well-documented, and on schedule.

Conclusion

Medical grade silicone is a precise technical category, not a general-purpose label. Specifying it correctly requires understanding the grade hierarchy (non-implantable, short-term implantable, long-term implantable), the certification landscape (USP Class VI, ISO 10993, FDA 21 CFR 177.2600), and how those certifications interact with your specific device's contact type, duration, and target market. Equally important is ensuring that the manufacturing process — the cleanroom environment, curing system, post-processing steps, and documentation chain — supports the compliance requirements your device must meet.

Getting these decisions right early, during design and material selection rather than during device validation, is what separates a smooth regulatory submission from a costly redesign. By combining a thorough understanding of medical silicone standards with a manufacturing partner who can maintain process consistency from prototype to production, product teams can move faster and with greater confidence at every stage of development.

Ready to Manufacture Your Medical Silicone Components?

NICE Rapid supports medical device teams from first prototype to full production — with LSR molding, silicone molding, compression molding, and a full range of complementary manufacturing services. Talk to our engineering team about your project requirements.