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Plastics in Medical Devices

by Arin Holecek

There are a wide range of plastics that can be used in medical devices.  Plastic selection depends on application as well as cost and manufacturability. 

Just some of the many plastics typically used in medical devices include polycarbonate, PMMA (acrylic), (PA) nylon, PVC (polyvinyl chloride), polypropylene, polyethylene, PTFE (Teflon), and ABS.  Here we will give a brief overview and talk about some applications for each.

polycarbonate framed-2

 

Polycarbonate
Polycarbonate is known for its strength, rigidity, and transparency. It is well-suited for medical devices because it can come in biocompatible grades and can be cleaned and sterilized using EtO (ethylene oxide), gamma irradiation, electron beam, steam autoclaving, and isopropyl alcohol. Polycarbonate can be injection molded, blow molded, extruded, and thermoformed. In addition, prototypes can be produced using milling and machining of blocks or rods.  Some typical medical device applications for polycarbonate include components used in renal dialysis, cardiac surgery (blood oxygenators, reservoirs, filters), IV connectors, other connectors such as stop cocks, y-injection sites, and check valves, filter housings, and surgical instruments such as trocars. In addition, polycarbonate films can be used in sterile medical packaging. More information on polycarbonate in medical devices can be found here:

https://www.thomasnet.com/articles/plastics-rubber/polycarbonate-medical/

PMMA framed

 

PMMA
PMMA stands for polymethyl methacrylate (also known as plexiglass, it is the most common type of acrylic) and is used for medical devices requiring impact strength, chemical resistance, biocompatibility, and clarity.  It is also used in bone cement, contact and intraocular lenses, screw fixation in bone, filler for bone cavities and skull defects, and vertebrae stabilization in osteoarthritic patients.  PMMA has high compatibility with EtO, gamma irradiation, and electron beam sterilization.  It can be cast into sheets, injection molded, extruded, thermoformed, and machined. More information on PMMA can be found here: 

https://pubmed.ncbi.nlm.nih.gov/16393131/ 

https://modernplastics.com/industries/medical-grade-pastics/

Nylon framed

PA/Nylon

 

PA stands for polyamide, one type of which is nylon (Nylon 6).  Another type of nylon is Nylon 66 (polyhexamethylene adipamide).  Nylon is good for use in medical tubing such as catheters and dilation balloons due to its excellent abrasion resistance.  Nylon is lightweight, strong, crush & cracking resistant, tear & puncture resistant, and flexural fatigue resistant.  Nylon is also commonly used as suture material and medical packaging.  It has high compatibility with EtO sterilization and fair compatibility with autoclave, dry heat, gamma irradiation, and electron beam sterilization.  Nylon can be injection molded, extruded, thermoformed, and machined.

https://www.dukeextrusion.com/materials/nylon-medical-extrusion        

PVC framed

PVC

 

PVC stands for polyvinyl chloride.  PVC is known for being flexible, durable, chemical resistant, biocompatible, having good clarity/transparency, and for being cost effective and recyclable.  PVC makes up approximately 40% of all medical device plastics used in hospitals.  It can be sterilized with steam autoclaving, EtO, gamma irradiation, and electron beam sterilization.  Typical applications include blood bags, medical tubing, oxygen masks, catheters, endotracheal tubes, IV infusion sets, nasal cannulas, ostomy bags, surgical gloves, blister packs, mattress covers, and medical mannequins.  PVC can be injection molded, thermoformed, extruded, and machined.

https://pvcmed.org/healthcare/medical-devices

 

 

 

 

polypropylene framed

 

 

 

 

Polypropylene
Polypropylene is cost-effective, has high stiffness and good impact/rigidity balance, has high compatibility with steam sterilization and EtO, and fair compatibility with dry heat, gamma irradiation, and electron beam sterilization.  It has good recyclability and can be injection molded, extruded, made into film, and machined.  Polypropylene is used in drug-delivery systems, nonwoven fabrics, packaging, syringes, pouches, test tubes, beakers, pipettes, and medical implants.  One particular heat-resistant grade proves to have good resistance to cleaning agents and disinfectants and is used in surgical trays and caddies.  Polypropylene is well suited for living hinges because of its good fatigue resistance.

https://www.farmpd.com/farm-blog/medical-device-materials-turn-up-the-steam-with-polypropylene

https://www.creativemechanisms.com/blog/all-about-polypropylene-pp-plastic                                                    

https://aipprecision.com/machining-polypropylene-pp-a-plastics-guide/ 

 

 

 

 

 

 

 

 

 

 

 

 

polyethylene with frame

Polyethylene

 

HDPE (high density polyethylene, LDPE (low density polyethylene), and LLDPE (linear low density polyethylene) are the most common polyethylene polymers used in medical applications.  Polyethylene is lightweight, chemically inert, and impermeable, making it well-suited for use as catheter tubing and packaging.  It has a low coefficient of friction and is highly crack resistant, making it good for use in dilators and sheaths.  Polyethylene is flexible and can withstand repeated flexing over long periods of time.  Polyethylene can be injection molded, blow molded, extruded, made into film, and machined.  It has good compatibility with EtO, gamma irradiation, and electron beam sterilization.

UHMWPE (ultra high molecular weight polyethylene), used for bearing surfaces in hip and knee replacements, is wear and impact resistant, has good ductility and toughness, and good chemical resistance. More information on polyethylene can be found here:

https://www.sciencedirect.com/topics/medicine-and-dentistry/polyethylene

https://modernplastics.com/industries/medical-grade-plastics/

ptfe framed

PTFE/Teflon

 

PTFE stands for polytetrafluoroethylene.  It is non-stick, flexible, and has high chemical, electrical, and thermal resistance.  PTFE is inert in blood or tissue, and good for use in in-body applications.  It is not useful for load-bearing applications.  PTFE can be made into porous membranes for filters, and it can be reinforced with glass, carbon, or bronze.  It is commonly used as a coating for medical guide wires, electrosurgical blades, forceps, and catheters. http://www.surfacesolutionsgroup.com/capabilities/ptfe-medical-components/.  PTFE can be injection molded, compression molded, extruded, and machined.  https://www.aspseal.com/Molded-Machined-PTFE.html.  It has good compatibility with EtO sterilization and fair compatibility with autoclave and dry heat sterilization.   More information on PTFE can be found here:

https://www.meddeviceonline.com/doc/an-introduction-to-emerging-polymers-for-medical-devices-0001                  

https://modernplastics.com/industries/medical-grade-plastics/                 

ABS framed

ABS 

 

ABS stands for acrylonitrile butadiene styrene and it is inexpensive, strong, and stiff, and has good recyclability.  It is used for a wide range of medical applications including tissue culture trays, test tubes, diagnostic components, and housings for test kits and medical devices.  It is known for its clarity (but with additives can have good opacity).  ABS has high compatibility with EtO, gamma irradiation, and electron beam sterilization.  ABS can be injection and blow molded, and it is good for use in 3D printing and prototyping because it can be easily machined, sanded, and painted. More information on ABS can be found here: 

https://www.creativemechanisms.com/blog/everything-you-need-to-know-about-abs-plastic              

       

     

For more information on plastics in medical devices, a well-detailed plastic selection guide comparing cost, mechanical properties, electrical insulating properties, temperature resistance, and chemical resistance can be found here: https://www.curbellplastics.com/Research-Solutions/Technical-Resources/Technical-Resources/Plastic-Material-Selection-Guide.  Additionally, a good summary and comparison of material properties can be found here: https://saliterman.umn.edu/sites/saliterman.dl.umn.edu/files/general/medical_device_polymers.pdf

This site provides more details on plastic chemistry and overall usage, not just in medical devices: https://www.essentialchemicalindustry.org/polymers/polychloroethene.html

And this site provides a good summary of plastic compatibility with different sterilization methods:

https://marketing.industrialspec.com/acton/attachment/30397/f-0048/1/-/-/-/-/plastics-sterilization-compatibility-chart-from-is-med-specialties.pdf

Contact us today – we can help you design your next plastic application:  http://www.zewskicorp.com/contac

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