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Biomedical Polymers and Compounds™

medical polymers

FDA Biological Testing of Medical Device Materials

Prior to marketing a device, the FDA requires biological evaluation to determine potential toxicity resulting from contact of component materials with the body.  The intention of such testing is to ensure device materials do not produce adverse local or systemic effects; are not carcinogenic; or, do not produce adverse reproductive and developmental effects. 

Nano Reinforcement of Medical Polymers

Enhancing strength and rigidity of polymers used for non-medical applications is often achieved by adding glass, carbon, and other fibrous materials to the polymer during melt compounding.  These fillers are too large for the extremely small geometries and thin wall sections of minimally invasive medical devices.  In such applications, nano clay reinforcement of polymers is far more effective. 

Material Changes for FDA Regulated Medical Devices

Changes in formulations of materials used for manufacturing patient-contacting medical devices or device components often require submission of a new 510(k) by the device manufacturer.  This is because formulation changes can affect the biocompatibility, material properties and performance of a device.

Silicones in Medical Devices

Silicones are widely used in medical devices because they are biocompatible, biodurable (do not degrade over time), do not produce extractables (a concern with leaching plasticizers from flexible PVC), and are unlikely to cause allergic reactions (a concern with latex).  Medical applications for silicones are far ranging from wound care gels to flexible drainage tubes to semi-rigid implants. 

Catheter Pushability and Navigation

Two common criteria for catheter shafts are pushability and navigation.  Pushability refers the force applied by a physician to advance the catheter to the designated therapeutic site.  Navigation refers to the ability of the catheter shaft to move freely through the non-linear vascular pathway.

PVC Remains Relevant in Medical Devices

Polyvinyl chloride (PVC) represents as much as one-third of the volume of polymers used in the manufacture of medical devices.  Common device applications for PVC include intravenous (IV) tubing and blood bags.  Environmental and health advocates have expressed concerns for years regarding the use of the polymer in medical applications, and the FDA issued an advisory warning regarding the health risks of PVC several years ago; however, this has not stopped the use of this economical polymer in the competitive medical device market.

The Versatility of Medical Thermoplastic Urethanes

Thermoplastic urethanes (TPUs) fall within a class of materials known as thermoplastic elastomers (TPEs).  Yet, TPUs comprise a class of materials unto themselves due to versatility in the polymer chemistry.  As such, there are many types of medical TPUs, with distinctly different properties. 

The Language of Medical Catheter Polymers

Durometer is arguably the most common polymer attribute discussed by medical catheter engineers.  For example, an ‘80A thermoplastic polyurethane (TPU)’ reference includes the durometer: 80, A scale. A measure of polymer hardness, durometer is directly applicable to certain catheter requirements. Soft polymer tips minimize vascular trauma. Harder catheter liners are necessary to resist abrasion from wires and instruments. Durometer also correlates to modulus, a measure of polymer flexibility that is important for catheter shafts.

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