(202a) Cellulose Nanocrystal Thermoplastic Urethane Composite Filament for Fused Filament Fabrication

Authors: 
Bortner, M. J., Virginia Polytechnic Institute and State University
Fallon, J., Virginia Polytechnic Institute and State University
Foster, E. J., Virginia Tech
Improving material selection for the fused filament fabrication (FFF) process has gained significant attention in recent years. Several researchers and companies have been pushed by consumers and industry to stretch the capabilities of the FFF process. FFF was originally developed as a prototyping tool and is now progressively challenged each day to produce end use parts for a wide variety of applications. We have built on the development of a smart mechanically dynamic material, one which can respond to changes in environment with minimal energy input, to potentially increase design freedom and realize new opportunities for expansion of FFF into new functional products.

This study focuses on the production of thermoplastic urethane (TPU)/ cellulose nanocrystal (CNC) filaments for use in FFF. We investigate the influence of various melt processing parameters on the stimuli-responsiveness of the adaptive thermoplastic nanocomposite filament. The composite system analyzed is composed of Texin® RxT70A with 10 wt% dispersed CNC, generated through a mast batching process. Randomly oriented film samples are created via solvent casting and uniaxially oriented samples are created via single screw melt extrusion. The orientation of each sample is characterized by both polarized Raman spectroscopy and small angle X-ray scattering (SAXS). Dynamic mechanical analysis results indicate that uniaxial orientation does not significantly impact dry or wet state modulus, likely resulting from a change in the percolating nature of the CNCs. Thermal history imparted by the single screw extrusion process has a negligible impact on the functionality of the CNCs and the corresponding responsiveness of the composite.