Compare products (0)
| Image |
|---|
| Price |
| Vendor |
| Product type |
| Tags |
| Description |
Food-grade, skin-friendly and medical silicone
Food-safe, skin-friendly and medical silicones
What do USP Class VI, ISO 10993, FDA and food contact actually mean? And which silicone do you choose for a mould or product that touches food, skin or the body? A practical guide to making the right choice, plus an honest picture of who is responsible for what.
Why silicones are used so widely
In many applications silicones are considered relatively safe. They are often biocompatible, oxygen-permeable and, once cured, generally contain no large amounts of harmful substances. That is why you find silicones in products that touch food, in contact lenses, implants, prostheses and even in dressings for scar tissue.
One thing to know up front: not every silicone is suitable for every purpose. Whether an end product truly meets the requirements for food or skin contact depends both on the material and on the way you process it. This page explains both sides.
The two main types of silicone
Chemically, we divide silicone rubbers into two groups. That distinction largely determines whether a silicone is suitable for food, skin or medical use.
1. Condensation-cure silicones
These silicones cure with a catalyst based on tin (or tin compounds). They come as:
- a ready-to-use 1-component sealant (the familiar silicone sealant), or
- a 2-component system (RTV-2).
Condensation silicones are mainly used for moulds in art and industry that do not come into contact with food. Most are not suitable for food contact. The reason: the curing reaction continues slowly, so the material keeps releasing residual products. In addition, the raw materials used are generally less pure than those in addition silicones. There are a few exceptions, such as Wacker E41 and E43.
2. Addition-cure silicones
These cure with a platinum or peroxide catalyst. They come in three forms:
- RTV-2 (platinum): a 2-component set that cures at room temperature. Widely used by craftspeople, hobbyists and smaller businesses for which the high investment of an LSR injection machine is not viable.
- LSR (platinum, injection): a 2-component set processed under pressure by injection machines. Less fluid than RTV-2, but considerably stronger. Often used for food-grade, baby-safe and sanitary products.
- HTV (peroxide or platinum): 1-component high-temperature vulcanising silicones. Used for food-grade moulds and other strong end products.
Important: only some addition silicones qualify as food-safe, skin- and medically compatible. Virtually no condensation silicone (category 1) does. Addition silicones with a peroxide catalyst must always be post-cured, and sometimes a scavenger must be added to remove residues of peroxide or acid, before it is meaningful to have the product tested.
The standards explained: USP Class VI, ISO 10993, FDA and food contact
Customers often ask about these abbreviations. Below is a short, concrete summary of what they mean, so you know which standard is relevant for your application.
USP Class VI
A US biocompatibility standard (United States Pharmacopeia, chapter <88>). The strictest of the USP classes. A material must pass three in-vivo tests: systemic toxicity, an intracutaneous (under-the-skin) reaction and an implantation test. Frequently requested for medical and pharmaceutical applications.
ISO 10993
The international standard for the biological evaluation of medical devices and the relevant standard for the European market. ISO 10993 does not assess the bare material but the end product in its final form, including processing and sterilisation method. More extensive and more differentiated than USP Class VI.
FDA
The US FDA sets requirements for materials that come into contact with food. A silicone may meet the FDA requirements that apply to the material itself, but that is different from a certified end product.
Food contact (incl. BfR)
In Europe, food contact is assessed partly through the guidelines of the German BfR. As with the FDA, this concerns the suitability of the material within the stated conditions, not an automatic approval of your end product.
The most common misunderstanding
USP Class VI and ISO 10993 are not a "certificate for a material". They assess whether an end product in its actual use form complies. The same silicone tube can be biocompatible in one product and not in another, depending on sterilisation method, contact duration and the other components. A material that passes USP Class VI usually also meets many of the requirements of ISO 10993, but the reverse does not apply automatically.
The logic behind this: only the behaviour of the part that comes into contact with the body or with food is relevant. Everything that precedes it in the process plays no role in the assessment, but does determine whether your product passes.
Which silicone do you choose for what?
| Application | Recommended type | Note |
|---|---|---|
| Mould for art or industry (no food or skin contact) | Condensation RTV-2 or addition RTV-2 | Most affordable route; no food/skin requirements needed |
| Mould for food (chocolate, sugar, ice) | Addition RTV-2 or HTV with food-grade label | Post-cure as prescribed; processing determines the result |
| Skin contact / body casting / prosthetic work | Platinum addition, labelled skin-friendly | Platinum, not condensation; mind skin sensitivity |
| Medical or series end product | Platinum addition / LSR in the right grade | The end product itself must be tested and certified |
Who is responsible for what?
We, and most suppliers, never certify that a product you make with silicones, colourants and other additives is food-safe, skin-friendly or of medical quality. This is not unwillingness but a logical consequence of how these certifications work.
However clean and safe the raw materials are, certifications apply only to end products. A product is only assessed and certified once it has been formulated clean and non-toxic, processed with suitable equipment in an appropriate environment (often a cleanroom), fully cured and post-cured, packaged correctly and reliably sterilised. Only then can the whole be tested and approved.
On the basis of the above, Silicones and More accepts no liability for the outcome of tests, nor for the success or failure of a project. We supply the materials with the best available information; the processing and certification of the end product are your responsibility.
How to approach a food-grade or medical product
Products in our webshop that carry the added note "food-safe" or "skin-friendly" generally meet, on their own, the relevant FDA and BfR requirements that apply to that product. Provided they are processed correctly, they are therefore unlikely to be the cause of any rejection of your end product. The route looks like this:
- Choose a silicone labelled FDA, food grade or skin-friendly.
- Process it exactly as prescribed, and do the same with all your other ingredients.
- Ensure quality control, suitable packaging and, where needed, sterilisation.
- Have the end product tested by an expert, independent third party.
- Does it fail? Find the bottleneck, adjust the process or ingredients and test again.
This route costs time and money, but the result is entirely yours and cannot simply be copied. It gives you an edge with customers who prefer certified products.
A recurring effort
A tested and certified product line requires maintenance. Assess quality regularly, keep your process accurate and repeatable (which often requires ISO standards) and have external tests carried out periodically. If you change your material, processing or sterilisation, biocompatibility must be reassessed.
Frequently asked questions
Is a food-grade silicone automatically suitable for medical use?
No. Food grade and medical are different requirements with different tests. Medical use generally requires biocompatibility testing such as USP Class VI or ISO 10993 on the end product.
Why is condensation silicone usually not food-safe?
The curing reaction continues slowly, so the material keeps releasing residual products. The raw materials are also generally less pure than those in addition silicones.
What is the difference between USP Class VI and ISO 10993?
USP Class VI assesses the material as a whole with three strict in-vivo tests and is mainly used in the US. ISO 10993 is the European standard and assesses the end product in its actual use form, including processing and sterilisation. ISO 10993 is more extensive and more differentiated.
Can Silicones and More certify my end product?
No. Certifications apply only to end products and depend on your complete processing. We supply materials with the available product information; testing and certifying the end product is something you have carried out by an independent specialised company.
Do I need to post-cure addition silicones?
For many food-grade and medical applications post-curing is required, and for peroxide-catalysed silicones almost always. Post-curing removes volatile residues. With peroxide systems a scavenger may be needed to remove peroxide or acid residues.
Not sure about the right choice?
Need help choosing the right silicone for a food, skin or medical application? We are happy to think along with you about material choice and processing.
Get in touchThis information is intended as general guidance and does not constitute a guarantee or certification. The suitability of an end product for food contact, skin contact or medical use must always be established on the final product, tested by a qualified independent company. Always check the current TDS, SDS and product specifications.