Cellulose Nanocrystals as Filler for Polymers

In a new publication, Supervisory Research Materials Engineer Gregory T. Schueneman reports on his research with cellulose nanocrystals (CNCs). CNCs are a class of renewable bionanomaterials with excellent mechanical properties that have attracted interest as filler for polymers. However, challenges associated with effective CNC dispersion have hindered the production of composites with desired property enhancements.

In Schueneman’s research, composites of polypropylene (PP) and low-density polyethylene (LDPE) with 5–10 wt% unmodified CNC are being produced for the first time with a solventless process, solid-state shear pulverization. Optical and electron microscopy revealed that the CNC dispersed very well and that degradation was strongly suppressed relative to composites made by melt mixing.

Field emission (FE) scanning electron microscope (SEM) images of as-received CNC at different weights.

Field emission (FE) scanning electron microscope (SEM) images of as-received CNC at different weights.

Taking thermal stability into account, this study has produced polyolefin/CNC composites with superior dispersion and property enhancements and has shown that CNC is an attractive and green filler for polymer composites. Over 50 million tons of plastic resins are used annually in the United States to manufacture products for a variety of end uses, including packaging, building materials, vehicles, furniture and furnishings, and electronics and electrical devices.

In this study, solid-state shear pulverization was used for the first time to produce composites of polyolefins and unmodified CNC. Microscopy and improved crystallization rate reveal excellent dispersion and suppression of CNC degradation within the polymer compared with composites made by melt mixing.These composites exhibit substantially greater stiffness, the greatest improvement ever reported for such composites made with unmodified CNC.

This study showed that CNC is an attractive and green filler for polymer composites.

The publication, titled “Cellulose nanocrystal/polyolefin biocomposites prepared by solid-state shear pulverization: Superior dispersion leading to synergistic property enhancements,” will be available online shortly. Cooperators include the USDA Forest Service Forest Products Laboratory, Madison, Wisconsin, and Northwestern University, Evanston, Illinois.