Clay Reinforcements Add Torque to Thin Wall Catheters and Improve Burst Strength in Balloons

Clay reinforcements are being investigated by the medical device industry as a means to improve the performance of device components. Specialist US medical compounder Foster Corporation remains at the forefront of polymer, additive and processing technology, with reinforced polymers for a variety of applications, including extruded thin wall catheters for diagnostics and stent delivery, as well as other minimally invasive devices.

Polyamide-based polymers, including nylon 12 and polyether-block amide—for example Arkema’s Pebax and Evonik’s Vestamid brands—are popular material choices for catheters used in diagnostic and interventional cardiology. The use of reinforced polyamide blends has been shown to yield significant improvements in the mechanical properties of the device, including an increase in flexural modulus, with only a moderate reduction in tensile elongation. Improvements can also be seen in increased burst strength for stent delivery balloons. In catheter shafts, the use of these materials can also improve torque transmission, which translates to an accurate navigation of the catheter through the vascular system.

Clay-reinforced polymers incorporate particles which have at least one dimension that is less than 100 nm, with aspect ratios in the 300:1 to 1,500:1 range. These particles interact at the molecular level to immobilise portions of the polymer chain, creating a reinforcing or stiffening effect that is unmatched by other strengthening agents. Utilising clay particle reinforcement can deliver rigid thermoplastic or elastomeric composites with unique performance properties.

While reinforcement additives can improve mechanical strength, manufacturing this technology can pose several challenges, due to the inherent nature of the clay. In order to prevent agglomeration (or clumping) of the particles, the compound must be specially formulated and processed to promote exfoliation. This process will allow the polymer chains to fully encapsulate the clay particles to create an intimate bond within the polymer matrix. Failure to produce a sufficient bond can lead to erratic processability and reduced compound performance.

Foster Corporation has developed advanced twin-screw compounding technology, as well as formulation expertise, proven to yield maximum dispersion of the polymer-particle blend, while avoiding host polymer degradation. Foster’s reinforced compounds are said to be able to be designed to achieve strict regulatory compliance, while delivering unique properties that can revolutionise the performance of complex medical devices.