What plastic is used for medical devices?

The answer is thermoplastics, but this includes numerous plastics. Thermoset plastics used for medical-device manufacturing do exist but have limited use.

The biggest difference between thermoplastics and thermosets is what happens when heat is applied. Thermosets become stronger while thermoplastics liquefy. Thermoplastics can be reheated and remolded multiple times without irreversible degradation. The changes are physical, not chemical. When heated, thermoplastics melt, and the material becomes moldable before solidifying into the finished product when cooled.

This guide covers:

• Why is plastic used for medical equipment?
• Most common plastics used in medical devices
• Application of plastics in medical devices and equipment
• Plastic medical-device manufacturing

	Pros	Cons
Thermoplastic	- Extremely adhesive to metal - Recyclable – can be remolded and shaped - Outstanding impact resistance - Excellent corrosion resistance - Electrical insulation - Flexible - Detergent and chemical resistance - Aesthetic finishes	- May soften when reheated - Can be more expensive than thermoset
Thermoset	- More resistant against high temperatures - Hard and rigid - High mechanical property - Cost effective - Excellent dimensional stability - Aesthetic finishes	- Cannot be recycled, remolded or reshaped - Difficult to surface finish - Poor thermal conductivity - Rigidity of material can result in product failure when used in high-vibration applications

There are multiple reasons for plastics used in medical devices. First and foremost is the isotonic saline solution that comprises our bodies’ extracellular fluid. This solution is highly hostile to metals but won’t degrade synthetic high-molecular-weight polymers, i.e., plastics.

Plastic medical devices have had a profound impact on medicine. It’s fair to say that plastic medical-device manufacturers are on the right track due to the material’s advantages over metal. Surgical gloves, syringes, and IV tubes are just some examples of sterilised devices available, thanks to plastics. Plastic is also durable and extremely easy to clean and sterilise, with a performance on par with metal in areas such as strength-to-weight/stiffness.

Why is plastic used for medical equipment?

Medical device plastic components are everywhere, and with good reason.

1. One-time use stops spread of infections

Many plastic surgical tools can be thrown away after one-time use, which inhibits the spread of infections.

2. Practical choice for manufacturing

When complex and intricate geometries and textures are involved, the flexibility of plastics as relative to metals makes good sense. Plastics can also provide metal-like robustness and strength.

3. Lightweight and ergonomic

Minimising hand fatigue during surgery is critical, and one way to do that is with plastic medical-device components. Metals are heavier, while plastics are lighter and easier to handle. Minimising weight increases mobility, which makes components easier to use.

4. Economical

Manufacturing with plastic resins is more affordable than metals, whether at high or low volume. Plastic is also cheaper to store and ship, as it’s lightweight. By focussing on lower-cost solutions, manufacturers can make affordability a key benefit to their products.

5. Compatibility

Plastic materials used in medical devices manufactured from injection moulding offer superior compatibility with imaging and X-ray machines compared to metals. Metals can hamper the magnetism of MRI machines and create interference with equipment that features WiFi and Bluetooth. Plastic materials for medical devices generate more accurate images.

6. Recyclability

The healthcare industry is looking for ways to lower its carbon footprint, and recyclable solutions is the way forward when possible. Certain plastic medical applications can be recycled, such as polypropylene sterilisation wrap, irrigation bottles, basins, pitchers and trays.

Most common plastics used in medical devices

The best plastics for medical devices are those that suit the application. When the plastic has patient contact, it should be medical grade, meaning it’s biocompatible with the body’s biological system. To learn what this encompasses, read our medical grade plastics article.

Antimicrobial plastic medical devices

An antimicrobial plastic is a synthetic polymer material. It contains an active ingredient to protect against microbial growth on surfaces and plastic materials used in medical devices. Antimicrobial additives are integrated into the plastic or applied as a coating during manufacturing and will remain an effective, active agent against bacteria, mould and mildew during the device’s lifetime.

Let’s look at the most common types of plastic used in medical devices. Can PVC be used in medical devices? It happens to be one of the most popular plastics for many medical applications. But which plastics to use in medical devices will depend on multiple factors.

Polyvinyl chloride (PVC)

PVC is flexible yet provides reliable strength and durability. With excellent chemical resistance, it can be sterilised by steam, ethylene oxide or radiation and still retain its properties. PVC resists tears and kinks, making it ideal for flexible plastic tubes for medical devices. It can be formulated for transparency, a critical factor when the visibility of fluids and gases is necessary. PVC also has good chemical stability, retaining its composition and properties when exposed to different liquids.

PVC Applications: Blood and dialysis bags, IV bags and tubing, blister packaging, oxygen masks, oxygen tubing, surgical gloves and gowns, and catheters

Polyethylene (PE)

PE resists impacts and corrosion while absorbing very little water. Even after repeated sterilisation cycles, it retains its overall performance and structural integrity. This is a porous polymer, biologically inert, and does not degrade in the body, making it an ideal material for implants. PE can also be used for single-use applications, stopping the spread of disease and infection by eliminating the need to sterilise devices. Its popularity soared during the COVID-19 pandemic with the need for sanitation products and personal protection equipment.

PE Applications: Implants, PPE equipment, catheters.

Polypropylene (PP)

An economical choice, PP has high chemical resistance, withstanding cleaning detergents and disinfectants. It also resists stress, cracking, impact and fatigue. PP has high dimensional stability, especially when put through repeated steam-sterilisation applications. Good machinability makes manufacturing processes easier.

PP Applications: Disposable syringes, membranes for membrane oxygenators, connectors, non-absorbable sutures, finger-joint prostheses, reusable plastic containers, prescription bottles, surgical trays, implant caddies.

Polystyrene (PS)

With a high electrical insulation and low dielectric constant, PS does not conduct electricity. It’s tasteless and odourless, which also makes it ideal for food containers. An economical option, PS has excellent gamma radiation resistance but poor chemical and UV resistance. However, like all polymers, desired qualities can be added. It’s also a naturally transparent polymer with good stability. PS is lightweight, with excellent insulating properties.

PS Applications: Culture trays, test tubes, petri dishes, diagnostic components, housings for test kits and devices, implants.

Polyethylene terephthalate (PET)

PET is a strong and inert material that resists attack by micro-organisms. It boasts high uniformity, resistance against chemicals and/or abrasion, and mechanical strength. Its biological characteristics include biostability, promoting tissue ingrowth. Those characteristics, coupled with its lightweight nature, is why it’s long been used in implants. Ideal as extruded plastic medical devices.

PET Applications: Extrusion of sutures, implantable textiles and tubing for angioplasty balloons, sewing cuff of heart valves (to promote tissue ingrowth and to provide a surface to suture the valve to the surrounding tissue). Also: vascular prostheses, cuff to stabilise catheter location and minimise bacterial migration through skin.

Acrylonitrile Butadiene Styrene (ABS)

Tough and rigidity durable, ABS plastic medical devices resist chemicals and impacts. This makes ABS a good replacement for metals in structural parts, and why plastic components for medical devices are a good choice. It can be sterilised by either gamma radiation or ethylene oxide. ABS also has good dimensional stability and insulating properties.

ABS Applications: Medical masks, valves for ventilators, non-absorbable sutures, tendon prostheses, drug-delivery systems, tracheal tubes.

Polycarbonate (PC)

PC is ideal in operating or A&E rooms. This is a lightweight material for easy handling, while also being strong and tough to prevent breakage. It’s also transparent, which is vital for visual inspections of fluids moving through a device. It retains its properties during sterilisation processes ethylene oxide gas, gamma or e-beam radiation.

PC Applications: Hemodialysers, infusion systems, anesthesia containers, blood oxygenators, blood reservoirs, arterial filters, intravenous connectors, surgical instruments and endoscopic appliances.

Acetal

Acetal possesses excellent creep resistance, making them a popular choice in applications that require dimensional stability. Acetal also has low water absorption, high wear characteristics, and good electrical properties. It also resists hydrocarbons, neutral chemicals, and solvents. Acetal is an excellent choice for plastic components of medical devices that require low friction, making them ideal for mechanisms that slide. It’s also a type of plastic used for medical imaging devices.

Acetal Applications: Handheld diagnostic wands, sterilisation trays, dental instruments, imaging equipment.

Polysulfone (PSU)

If the application will need sterilising after repeated use, polysulfones are a good material choice. It can be sterilised time after time without degradation. With high-impact strength and good mechanical strength, PSU is dimensionally stable and able to maintain tight tolerances. It resists mineral acids, alkali, and electrolytes and can be cleaned with bleach.

PSU Application: Transparent portion of anesthesia masks, heart valve sizers, dialysis filtration cartridges, outer shell of implantable catheter ports, surgical instrument cases and trays, dental instruments.

Polyurethane (PUR)

Flexible, strong and durable, PUR resists abrasions and chemicals. PUR is made of elastomers that closely resemble human proteins, making it compatible with the human body. Its molecular structure makes it unlikely that the material will be absorbed by the body, making it useful for inside the body. Non-allergenic, PUR is an excellent alternative to latex.

PUR Application: Implant devices: feeding tubes, dialysis devices, intra-aortic balloon pumps, surgical drains, pacemakers, artificial hearts. Also: hospital beds, surgical tables.

At a glance: Application of plastics in medical devices and equipment

This is a guide only. For brevity, we’ve simplified many of the applications. For example, PUR is listed here for implants, but not the specific types of implants the material is typically used in. There are also different types of trays, but not all materials will be right for all trays. To find more specific information about applications, see the section above or click on the material links below.

Medical device/equipment	PVC	PE	PP	PS	PET	ABS	PC	Acetal	PSU	PUR
Arterial filters							X
Artificial hearts										X
Blister packaging	X
Blood bags	X
Blood oxygenators & blood reservoirs							X
Catheters & catheter applications	X	X			X				X
Containers – reusable			X				X			X
Connectors			X				X
Diagnostic components				X				X
Dental instruments								X	X
Dialysis components	X						X		X	X
Drug delivery systems						X
Endoscopic appliances							X
Housings for test kits, devices & equipment				X		X
Heart valve sizers									X
Imaging equipment								X
Implants		X		X						X
Implant caddies			X
Inhalers						X
Insulin pens						X
Intra-aortic balloon pumps										X
IV bags	X
Masks	X					X			X
Medical furniture										X
Membrane oxygenators			X
Pacemakers										X
Petri dishes				X
Containers – reusable			X
Prescription bottles			X
PPE equipment		X
Prostheses			X		X	X
Sewing cuff – heart valves
Surgical gloves & gowns	X
Surgical instruments							X
Sutures			X		X	X
Syringes – disposable			X
Test tubes				X
Trays			X	X				X	X
Tubes	X				X	X				X
Valves – ventilators						X

 

Plastic medical-device manufacturing

Thermoplastics are perfect for plastic injection-molding for the medical-device industry, and injection blow-molding processes. But there are other processes, as seen below:

MATERIAL

COMPRESSION MOLDING

TRANSFER MOLDING

INJECTION MOLDING

EXTRUSION

ROTATIONAL MOLDING

BLOW MOLDING

THERMOFORMING

REACTION INJECTION MOLDING

CASTING

FORGING

FOAM MOULDING

REINFORCED PLASTIC MOLDING

VACUUM MOLDING

PULTRUSION

CALENDERING

Acetal

x

x

x

x

x

x

x

x

ABS

x

x

x

x

x

x

x

Polycarbonate

x

x

x

x

x

Polyethylene

x

x

x

x

x

x

x

x

x

Polypropylene

x

x

x

x

x

x

x

x

x

x

Polystyrene

x

x

x

x

x

x

x

x

Polysulfone

x

x

x

x

x

Polyurethane

x

x

x

x

x

x

x

PVC

x

x

x

x

x

x

x

x

x

x

x

PET

x

x

x

x

x

x

x

x

x

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