Samantha Deverell, managing director at Adtech Polymer Engineering, demonstrates how replacing a carbon atom with a fluorine atom changes the properties of a molecule and creates endless possibilities.
Thanks to their unique properties, fluoroplastic coatings can meet severe environmental conditions and allow for sensors to work in hostile environments. As such, fluoroplastics are ideal for protecting sensors in medical applications, from centrifugal evaporators to microwave treatments and steam generators.
Why fluoroplastics are ideal for medical applications
Also known as fluoropolymers, fluoroplastics are high-performance plastics with unique properties. The most common materials are PTFE, FEP, PFA, ETFE, E-CTFE, and PVDF. While a plastic molecule contains a carbon chain with hydrogen atoms attached, in a fluoroplastic molecule, the hydrogen atoms are replaced with fluorine atoms. This dramatically changes their properties and transforms them into high-performance materials with limitless possibilities.
Fluoropolymers enjoy exceptional medical properties. Not only are these materials inert and non-stick, fluoroplastics are also pure, non-toxic, bio-compatible and can be sterilised. Additionally, PTFE, FEP, and PFA benefit from other unique properties, including:
- Very high temperature resistance
- Total resistance to chemicals, acids and solvents
- Low friction characteristics and tensile strength
- Resistance to weather, UV light and corrosion
The maximum working temperature for an FEP coating is 200°C, and for applications that require a higher temperature, PTFE and PFA covers withstand 260°C. As such, fluoroplastics can meet severe environmental conditions and are ideal for protecting sensors in medical applications.
The benefits of fluoropolymer sensor coatings
Thanks to their unique properties, fluoroplastic coatings offer medical sensors the following benefits:
Protection against high temperatures and chemicals
- Protection against excessive pressure, material velocity and corrosion
- Increased lifespan
- Reduced risk of contamination
- Non-stick characteristic
All in all, fluoropolymers allow medical sensors to work in hostile conditions.
PTFE, FEP and PFA are relatively difficult materials to process, but by using a combination of moulding, heat shrinking, welding, and spraying techniques, coatings can be applied without damaging delicate sensor elements inside.
Medical sensor covers can be produced using FDA-compliant and USP class VI compliant raw polymers. In addition, custom covers can be produced to fit specific design requirements.
The use of fluoroplastic coated sensors in medical applications
Fluoropolymer coated sensors find use in medical treatment, health monitoring, and medical research, and can measure temperature, pressure, liquid level, oxygen, radiation and more.
For example, fluoroplastic coated sensors are useful for monitoring temperature in centrifugal evaporators and sample concentrators. In this particular application, the sensor is encapsulated in FEP heat shrink. A weight is usually added at the tip to ensure the component stays in the vial when the centrifuge is spinning. Additionally, the covers can include a strip of colour for identification purposes.
Fluoropolymers are ideal to cover sensors suitable for microwave treatment for patients. For this application, the coatings are designed to feature a hemispherical-domed tip with a consistent wall thickness at the sealed tip in order to control each dose of microwave treatment. The sensor is completely encapsulated and is suitable for immersion into liquids without fear of ingress.
PTFE also finds use in water level detection sensors for steam generators. Known as plugged PTFE probe covers, heavy wall PTFE tubes are usually plugged and welded to ensure the component is completed sealed and there is no chance of ingress. In this particular application, the coatings are thicker to protect against the high pressure in the steam vessel.
