Plastics in medical technology: which materials are suitable?

Plastics are indispensable in modern medical technology. They are used in implants, instruments, single-use products or diagnostic devices and, depending on the application, must meet high requirements for biocompatibility, sterilizability, chemical resistance and mechanical properties.

However, not every plastic is automatically suitable for medical applications. In addition to the polymer itself, the specific material grade, the additives it contains, the manufacturing process and the intended type and duration of body contact all play an important role.

Requirements for medical technology plastics

Medical plastic parts must perform far more than many conventional technical components. Particularly in the case of direct or indirect patient contact, the biocompatibility of the materials used is the central concern.

Other important requirements are:

• Sterilizability: The material must be compatible with the intended sterilisation method, for example steam sterilisation, ethylene oxide or radiation sterilisation.
• Mechanical stability: Components must achieve the strength, dimensional stability and durability required for their application.
• Chemical resistance: Depending on the application, plastics must be resistant to disinfectants, alcohols, medicines, body fluids or cleaning agents.
• Material purity: Composition, additives and possible impurities must be taken into account, especially in applications close to the patient.
• Documentation and traceability: In the case of regulated medical devices, clear material specifications and traceable material batches play an important role.

What does "biocompatible" mean for plastics?

A biocompatible material is suitable for the intended biological contact without causing unacceptable biological risks. However, "biocompatible" should not be understood as a blanket property of an entire plastic type.

The biological evaluation of materials and medical devices is carried out, among other things, on the basis of the ISO 10993 series of standards. Which tests are required depends, for example, on the type of body contact and its duration. Material manufacturers also point out that biocompatibility must always be considered in relation to a specific material grade and application.

For design and purchasing, this means: The statement "PEEK", "polycarbonate" or "TPE" alone is not enough. For medical applications, it should be checked whether the specific material quality has the required evidence and specifications.

Suitable plastics for medical technology at a glance

Polypropylene (PP)

Polypropylene is frequently used for medical single-use products, laboratory articles, containers and other components. Its low weight, good chemical resistance and economical processing make PP interesting for numerous applications.

Whether a particular PP grade is suitable for direct patient contact must be assessed on the basis of the respective material specification.

Polyethylene (PE)

Polyethylene (PE) is one of the common plastics in medicine and laboratory technology. Possible applications range from containers and packaging to tubes and technical components.

For plastics in body implants, ultra-high-molecular-weight polyethylene (UHMW-PE) is particularly important. It is used, for example, for selected joint implant components. Other PE variants are also used in the medical environment.

Anyone procuring polyethylene sheets or PE semi-finished products for medical applications should therefore not select solely on the basis of the polymer designation. Required material evidence, batch, additive formulation and the specific application must already be taken into account when selecting the material.

Polyetheretherketone (PEEK)

PEEK is a high-performance plastic with high mechanical strength, temperature resistance and chemical resistance.

Special medical PEEK grades can be used for applications involving body contact and in some cases also for implants. PEEK is therefore one of the particularly relevant biocompatible plastics for demanding medical technology components.

Here too, it is important to distinguish between generally available technical PEEK and specially tested medical or implant grades.

Polycarbonate (PC)

Polycarbonate (PC) combines transparency with high impact strength and rigidity. These properties make the material interesting, for example, for transparent housings, containers and components of medical devices.

Is polycarbonate biocompatible? This cannot be answered across the board for every PC grade. Specially selected or tested polycarbonate grades are available for medical applications. For material selection, the specific grade, the intended patient contact and the required evidence should therefore be checked.

The sterilisation method must also be taken into account, as different methods can affect polycarbonate in different ways.

Polysulfone (PSU) and polyphenylsulfone (PPSU)

PSU and PPSU are suitable for numerous demanding technical applications thanks to their temperature resistance and good chemical properties.

Suitable PPSU grades in particular are used for reusable medical components where repeated cleaning and sterilisation are required.

TPE and TPU for medical applications

Thermoplastic elastomers (TPE) combine elastic properties with the processability of thermoplastics. TPU, i.e. thermoplastic polyurethane, is one of the technically particularly relevant elastic materials.

Suitable medical TPE and TPU grades can be used, among other things, for:

• tubes
• catheter components
• flexible connectors
• sealing and functional elements
• soft grips and contact surfaces

For medical applications, it must also be checked for TPE whether the specific material grade is suitable for the intended body contact and the required sterilisation method. Biocompatible TPU, PA and other polymer grades are offered specifically for medical applications, for example.

Thus the search query "Which TPE is suitable for medical applications?" is not answered by the material family alone: the selection depends on the type of contact, mechanical requirements, sterilisation method and the required regulatory evidence.

Fluoroplastics such as PTFE

PTFE has a very high chemical resistance and extremely low friction values. As a result, the material is a candidate for various technical and medical applications, for example in sliding components, seals or special medical components.

When using PTFE with direct body contact, too, the specific material quality and its evidence of suitability must be taken into account.

Which plastics are suitable for body implants?

Particularly high requirements apply to a plastic for body implants. Depending on the product, the material is in direct contact with tissue or body fluids for an extended period. In addition to mechanical load capacity and ageing resistance, an application-specific biological evaluation is therefore required.

The polymer materials used in certain implant applications include, for example:

• special implant grades of PEEK
• UHMW-PE
• PTFE or specially processed fluoropolymers
• other specially developed medical polymer materials

The general material designation does not in itself constitute approval for an implant. For a medical device, material, processing, intended body contact and regulatory requirements must be assessed together.

Typical applications of medical plastic parts

Plastics are used in very different areas of medical technology:

• Implants and prostheses: for example selected PEEK or PE grades
• Single-use products: including components made of PP or PE
• Diagnostics and laboratory technology: containers, analysis components and transparent parts
• Medical devices: housings, covers and technical functional parts
• Tubes and flexible components: suitable TPE and TPU materials
• Reusable instruments: temperature- and chemical-resistant high-performance plastics

For the manufacture of corresponding components, Martan Plastics offers not only plastic semi-finished products but also options for plastic machining.

Which biocompatible plastic is suitable for your application?

Material selection begins with the specific application. A material that is suitable for a device housing does not automatically meet the requirements of a catheter or implant.

When selecting, you should clarify in particular the following questions:

1. Is there direct or indirect contact with the patient?
2. How long does the contact last?
3. What mechanical loads occur?
4. Which chemicals or body fluids act on the component?
5. How is the product cleaned or sterilised?
6. What evidence of biocompatibility is required?
7. Is a semi-finished product, a cut piece or a finished machined plastic part required?

On this basis, suitable materials such as PE, PEEK, PC, PPSU, PTFE or TPE can be narrowed down in a targeted way. For specific medical technology projects, you will find further information on materials and manufacturing on our page Plastics for medical technology.

Frequently asked questions about plastics in medical technology

Which plastics are biocompatible?

The plastics for which special biocompatible grades are available include PEEK, PE, PP, PC, PPSU, PTFE as well as various TPE and TPU. However, biocompatibility should always be assessed for the specific material grade and the intended contact.

What are biocompatible materials?

Biocompatible materials are materials that are suitable for intended contact with biological tissue or body fluids without causing unacceptable biological risks. The evaluation is application-related and can include tests in accordance with ISO 10993.

Is polycarbonate biocompatible?

Certain polycarbonate grades are available for medical applications and have corresponding tests or material evidence. Not every commercially available polycarbonate should therefore automatically be classified as biocompatible.

Which TPE is suitable for medical applications?

Suitable medical-grade TPE and TPU are used, among other things, for tubes, flexible connectors, seals and other components close to the patient. The selection depends on the type of contact, contact duration, sterilisation method and the required evidence.

Which plastic is used for body implants?

Depending on the implant, special implant grades of PEEK as well as UHMW-PE and other medical polymer materials may be considered. For implants, a product-specific biological and regulatory evaluation is always required.

Where can polyethylene sheets for medical applications be obtained?

PE semi-finished products and polyethylene are available in various grades. For medical technology applications, you should state already in your enquiry what requirements apply to material grade, evidence, traceability and subsequent body contact.