Engineering polymers for medical injection moulding

Engineering polymers for medical injection moulding

There are many different types of polymers that can be used in the manufacture of medical components. Commodity thermoplastic materials are starting to be replaced with engineering polymers that can offer better performance qualities and increased stability.

These polymers have greater engineering properties than commodity materials but are more difficult to process. The end result in terms of the quality and stability they bring to medical components is, however, often worth the effort.

  • TPX (PMP) Polymethyl Pentene
    TPX (PMP) is a transparent polymer with a very high melting point. It is the lightest polymer available, has low moisture absorption and is chemical and heat resistant so is ideal for medical instruments and laboratory equipment that need to be sterilised or autoclaved. Other applications include optical components containing lenses and windows.

  • Copolyester
    Copolyesters are versatile, transparent resins that are impact and chemical resistant, retaining their mechanical properties when exposed to aggressive chemicals such as medical disinfectants and oncology drugs that would affect other polymers. Copolyesters perform well throughout the plastic injection moulding process and are suited to high speed, high volume production. Medical applications include IV components and connectors.

  • Polybutylene terephthalate (PBT)
    PBT has consistent mechanical properties, low moisture absorption and produces parts that have good dimensional stability. It performs particularly well during the injection moulding process allowing for faster cycle times. Applications include valves and connectors, clamps, clips, handles and sleeves for surgical, diagnostic and drug delivery devices as well as housings for monitoring equipment.

  • Polyethylene terephthalate (PET) 
    PET is a lightweight but exceptionally strong material with excellent mechanical and thermal properties combined with resistance to abrasives and chemicals. It is an inert material that promotes tissue growth and is anti-microbial so can be used for surgical implants. 

  • Polyamide (PA) Nylon
    Polyamide (PA) Nylon is a lightweight polymer that is strong and durable with exceptional resistance to corrosion and abrasion. It is heat and chemical resistant to oil, grease, solvents and detergent so is ideal for laboratory equipment, medical device components, tubing and surgical instruments that require frequent or repeated sterilisation.

  • Polyoxymethylene (POM or acetal)
    Known for its dimensional stability, POM is a rigid, hard and strong engineering polymer that is low friction and has good electrical insulation. It is a highly crystalline thermoplastic that is ideal for complex components due to its strength and machining ability. It offers excellent wear resistance and chemical resistance particularly to alkalis, disinfectants and solvents. Ideal applications include precision parts for drug delivery equipment, medical devices and orthopaedic instruments.

  • Polycarbonates (PC)
    Polycarbonates have high temperature and impact resistance which makes them easy to process without cracking or breaking. PC is transparent, lightweight and robust which makes it ideal for instruments used during surgical procedures. It is also resistant to gamma radiation and can handle tough sterilisation processes. Other devices PC is suited to include endoscopic equipment and dialysis components.

  • Polycarbonate/Acrylonitrile Butadiene Styrene (PC/ABS)
    PC on its own has poor chemical resistance. It is the acrylonitrile that provides the chemical resistance in ABS. PC/ABS produces a material that has the best of both worlds.

A lot of hospital electrical equipment and devices rely on the use of PC/ABS, PC, and ABS for the outer housing due to its glossy appearance and good impact strength. However, since the increase in outbreaks of viruses such as Covid-19, hospital maintenance teams must ensure all products are cleaned down with chemical solutions that are potent enough to kill such viruses. This results in a classic problem of PC/ABS mouldings that are potentially subject to cracking in hospital environments as the cleaning solution not only attacks the virus, but it also attacks the plastic housing itself, causing it to stress crack and fail.

Make sure your moulding supplier has worked with these materials in the past. With engineering polymers, mould tools can be more expensive due to the higher melt temperature. The moulds require designing with hot water circuits for pre-heating and for holding the tool temperature at a higher level than with the commodity polymers.

The thermoplastics we have covered here require precision processing which is a core competence of the OGM team. As demonstrated in this blog, we also have the capability to process even more challenging materials, including the thermoplastic superheroes – PPSU and PEEK.

If you are looking for a plastic injection moulding partner for your next project, we have state-of-the-art equipment, manufacture to medical standard ISO 13485 and have an ISO 7 cleanroom (Class 10,000 cleanroom). Contact our team.

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