What is medical-grade plastic?
We’ve put together this guide to help you understand exactly what the medical-grade definition encompasses for plastic materials. We’ll answer common questions, such as what is medical-grade plastic made from? We’ll also determine if biocompatible plastic material is the same as a medical plastic. We’ll cover:
What is medical-grade plastic used for?
Medical-grade plastic materials refers to plastics designed to make medical products and devices, ranging from prosthetics to syringes. It’s also used for manufacturing products for in vitro diagnostics and primary packaging for pharmaceuticals, which preserves and contains medicines to avoid contamination.
Medical plastic devices are commonplace. For instance, polyethylene uses in medicine vary. But polyethylene is also used in ordinary, everyday life as well as in industrial applications. It comes down to how you define medical-grade polyethylene.
What does medical grade mean?
Believe it or not, there is no regulatory definition of a medical-grade polymer. Standard ISO 10993 defines the requirements for materials that can be used for medical devices. In theory, manufacturers can therefore use any plastic in medical devices, as long as the entire device meets those requirements.
ISO 10993 certification verifies the biocompatibility of your medical devices.
In essence, ISO 10933 requires biological evaluation of, but are not limited to:
- Construction of material(s)
- Intended additives, process contaminants, and residues
- Packaging materials
- Leachable substances
- Degradation products
What does biocompatible mean? The biocompatibility definition is the same for any material: the device must be compatible with biological systems, meaning the human body.
The device that achieves ISO 10993 meets stringent requirements. ISO 10993 is considered the standard for medical-grade materials, even if technically, the materials are not medical grade.
Consequently, material suppliers and others in the medical-device industry have determined their own definition of what constitutes a medical-grade plastic. As a result, medical-grade polymers can vary in performance and quality from supplier to supplier.
That should change. The Association of German Engineers, VDI, published a voluntary guidance document outlining the meaning of medical-grade plastics. It’s not yet been adopted, but it could be a matter of time. The effect would require plastic medical-device manufacturers to prove they use consistent formulations.
What are the types of medical-grade plastics?
Medical-grade materials can include any plastic you want. Take polystyrene, a common polymer. Medical-grade-plastic manufacturers engineer the resins, with processes that enhance the qualities for biocompatibility. The results are polystyrene medical applications, from petri dishes to implants.
Medical-grade ABS plastic is another popular choice, used in drug-delivery systems and tracheal tubes. Polyethylene in medical applications includes catheters and surgical tools.
Medical-grade resins are appearing on the market in various materials, such as PEEK and Polyetherimide (PEI), but there is no hard-and-fast biocompatible plastics list to make life easier for designers. It depends on how the plastics are engineered to become biocompatible. Generally, a biocompatible plastic is designed to resist:
● Temperature
● Chemicals
● Corrosion
A medical-grade material should also be able to handle repeated sterilisation cycles and remain inert when coming into contact with living tissue and bodily fluids. Even single-use plastic devices in healthcare, despite being disposable, are sometimes required to be medical grade, meaning they need ISO 10993 certification to verify the device’s biocompatibility.
Plastics in medicine are incredibly common. You can find types of plastic used in medical devices in our guide, What plastic is used for medical devices?
USP class VI definition
What does USO class VI mean? While ISO standards are the most well known around the world for all materials, they’re not alone when it comes to polymers. The U.S. Pharmacopeial Convention (USP) dictates testing for plastic medical devices to evaluate biological responses of materials to the body, skin, and living tissue of live lab rats and mice.
The USP Class VI designation involves the most rigorous testing of the six classes and, therefore, most useful for medical applications. Their standards are recognised in 140 countries, including the UK. In the U.S., their standards are enforceable by the Food and Drug Administration (FDA). There are no FDA-approved plastics for medical devices. It’s the entire device that is tested, as variables such as manufacturing processes can alter the material’s properties.
USP Class VI: What does it mean to be medical grade?
“Test specimens” refer to lab rats or mice.
|
Systemic Injection Test |
Intracutaneous Test |
Implantation Test |
|
Test specimens injected with the extract intravenously and monitored for 72 hours to identify any reactions that relate to abnormal toxicity level |
Test specimen injected intracutaneously with the extract before being monitored for 72 hours; any skin reactions are scored and averaged |
Product materials implanted into the specimen to identify whether a reaction in live tissue takes place after coming into direct contact with product over a period of around five days |
In order to meet Class VI standards, the product/material must exhibit a very low level of toxicity.
The tests are similar to ISO 10993 and have some cross-over. However, the USP classification only outlines the tests needed. Unlike ISO standard, it doesn’t include the risk management of a plastic medical device.
ISO 10993: risk management
Risk analysis requires identifying and characterising all materials that have the potential to be in the final medical device. This will include analysing the presence of any manufacturing additives. Also, an examination of the impact of processing takes place on material composition and chemistry.
Analysis can include:
- Chemical interactions between materials
- Impact of physical degradation (wear, load, fatigue, friction)
- Environmental interactions (heat and thermal degradation, UV light and light-catalysed degradation)
- Manufacturing processes
- What additives will be used? Processing aids, such as such as catalysts, antioxidants, pigments, and surface treatments?
- What are the potential process contaminants?
- What are the potential process residuals of chemicals and additives?
- Decontamination and sterilisation systems
- Effect of contaminants from packaging materials
- How transportation, storage, and ageing will impact the material
USP Class VI vs. ISO 10993
USP Class VI demands an intracutaneous irritation test. So does ISO 10993. However, Class VI also requires subacute toxicity and implantation effects, which many ISO 10993 categories do not.
That said, the lack of risk assessment in USP Class VI can be a problem. It’s possible that a USP Class VI material can also comply ISO 10993. But USP Class VI by itself is not adherence to ISO 10993.
You can learn more in our guide, What are the material standards in medical manufacturing?
Advantages of medical-grade plastics
Plastics for medical devices offer several advantages over some other materials. Medical grade plastic material offers the following:
| Characteristic | Definition |
|---|---|
| Biocompatibility | Formulated for compatibility with the human body to prevent adverse reactions. |
| Sterilisation | Withstands various sterilisation techniques, such as gamma radiation, ethylene oxide gas, and autoclaving. |
| Durability | Resistant to wear and tear, making them ideal for use in plastic medical devices that require repeated use. |
| Versatility | Can be moulded into different shapes and sizes for manufacturing complex devices. To learn more, see our guide, Injection moulding for medical parts. |
| Lightweight | Typically lightweight, making them useful for implants. |
| Chemical and heat resistance | Withstands different chemicals and high temperatures, making them suitable for harsh medical environments. |
| Cost effective | More cost effective than traditional materials such as metal and ceramics. |
Is it safe to use medical-grade plastics?
Yes. Plastics in medical devices are deemed safe, as they are biocompatible.
Plastic, metal or any other material not designed to be biocompatible can have far-reaching consequences, which can be prevented or minimised by medical-grade devices. Those consequences include:
● Chronic inflammation at the area of contact
● Cytotoxic substances production
● Cell disruption
● Skin irritation
● Restenosis (narrowing of blood vessels after stenting)
● Thrombosis (forming blood clots)
Download free CADs and try before you buy
Download free CADs and request free samples, which are available for most of our solutions. It’s a great way to ensure you’ve chosen exactly what you need. If you’re not quite sure which product will work best, our experts are always happy to advise you.
Whatever your requirements, you can depend on fast despatch. Request your free samples or download free CADs now.
Questions?
Email us at sales@essentracomponents.co.uk or speak to one of our experts for further information on the ideal solution for your application 0345 528 0474.