Transmission electron microscopy image of freeze-dried CNCs that were redispersed in
deionized water and stained with aqueous uranyl acetate.
The Journal of Applied Polymer Science features groundbreaking work from FPL Materials Research Engineer Robert Moon and others. “Enhanced thermal stability of biomedical thermoplastic polyurethane with the addition of cellulose nanocrystals” by Jen-Chieh Liu, Darren J. Martin, Robert J. Moon, and Jeffrey P. Youngblood takes us to the world of nanocellulose in medical devices.
Thermoplastic polyurethanes (TPUs) are used in manufacturing biomedical devices, such as vascular grafts or ventricular assistance devices, where mechanical performance and biocompatibility and nontoxicity are crucial. However, to increase the range of biomedical device applications and improve end use performance, improved thermal stability during fabrication and the ability to controllably manipulate strength and toughness without loss of biocompatibility is required. And because these devices are to be used in the human body, they must be nontoxic. Cellulose nanocrystals (CNCs) are cellulose-based nanoparticles produced from wood or plant fibers. As candidates for nano-reinforcement materials for TPUs, CNCs work well because they have high mechanical properties, good thermal properties, and low toxicity.
In many cases, TPU fabrication (such as extrusion and injection molding) to make products involves high temperatures and long manufacturing time because of blending and homogenization. These factors degrade polymer chains and decrease mechanical properties. If nano-reinforced TPUs can achieve a higher decomposition temperature, they could be processed under a wider range of operation temperatures and manufacturing times without loss of mechanical properties.
This research showed that higher solid loadings of CNCs in a commercial TPU commonly used in biomedical applications resulted in a higher onset degradation temperature of the nanocomposite, providing a wider processing temperature for manufacturing products to be used in biomedical devices without loss of mechanical properties.
FPL cooperated with Purdue University; University of Queensland, Brisbane, Australia; and Georgia Institute of Technology, Atlanta, Georgia, on this project.