(643a) Comparison of Polymer-Microcrystalline Cellulose Composites with Polymer Nanocomposites Made with Carbon Nanotubes or Graphite: Processing by Solid-State Shear Pulverization

Solid-state shear pulverization (SSSP) is used to make two types of composites.  In the first case, composites of relatively well-dispersed microcrystalline cellulose (MCC) are produced using polypropylene (PP) or poly(lactic acid) (PLA) as the matrix.  In the case of PP, 20 wt% addition of  MCC yields a material with a 100% increase in modulus relative to neat PP.  This composite can be easily processed via injection molding into products using approximately the same molding conditions as for neat PP.  Such materials retain the “infinite hinge” characteristics of neat PP and may allow for the production of thinner parts than with neat PP. Composites of relatively well-dispersed MCC (at 1 wt% content) are made in PLA as a means of dramatically increasing the crystallization rate of PLA.  The MCC/PLA interfaces serve as nucleation sites for crystallization, which can overcome the grudgingly slow crystallization rate of PLA during injection molding.  Such semi-crystalline materials have high-temperature mechanical robust due to their semi-crystalline nature.  These systems will be contrasted with well-dispersed PP-carbon nanotube and PP-graphite nanocomposites made by SSSP.  Such materials yield major increases in mechanical properties, e.g., 50-100% increases in modulus at 1.0-2.5 wt% nanofiller content, and also provide for the possibility of multifunctionality in terms of both mechanical properties and electrical conductivity