Thermoplastic polyurethanes (TPUs) are used in medical devices due to their versatility and the range of properties that can be achieved through the various chemistries available for TPU formulation. The vast majority of medical TPU is optimized for melt processes (like extrusion and injection molding) that are used to create common TPU components such as catheter tubing. Medical TPUs often contain lubricants or other process aids and antioxidants to enable melt processing and protect the material against degradation from the elevated temperatures employed in these melt processes.
While extrusion and injection molding are driving a lot of the medical TPU business, a smaller subset of solution-based processes are key to enabling certain applications. Dip-coating, electrospinning, solvent casting, spray coating, and spin coating are among the more commonly employed methods in this category. In each of these processes, a polymer is dissolved in a solvent, the solution is manipulated into some physical shape, and the solvent is then removed, leaving the polymer behind.
The primary reason for selecting solution processes over melt processes is the thinness of the component or feature being created (e.g., coatings on metal stents), but other reasons can include the desire to incorporate drugs or other chemistries into the polymer matrix that could react or degrade at the elevated temperatures needed for melt processing.
Although solvent processes are analogous in some ways to melt processes, they each require distinct properties from the material. Some off-the-shelf TPUs might work at a crude level in solution processes, but they are not optimized for these processes.
To support customers who employ dip coating or other solution processes in their manufacturing, Biomerics offers solution grade versions of many of our Quadra™ and Elast-Eon™ materials. These solution grade (“SG”) TPUs are pellets that look just like the corresponding standard (melt) grades, but they are specifically formulated for solution processing in two ways.
- First, the SG TPUs omit the process aids and other additives that may not be soluble and could interfere with solution processing.
- Second, the stoichiometry of the monomers that react together to form the TPU polymer is slightly adjusted to reduce cross-linking and promote solubility.
These SG materials are provided in pellet form, ready to be dissolved by the customer for use in their solution processes.
If you are interested in learning more about our solution grades of Quadra™ or Elast-Eon™ TPUs, or if you have questions about how these materials may assist you in the design and manufacturing of your device, please contact our team via www.biomerics.com.
Director of R&D Materials