Chapter 1.4: Spatially Resolved Characterization of CNC-Polypropylene composite by Confocal Raman Microscopy

Abstract

Raman spectroscopy was used to analyze cellulose nanocrystal (CNC)-polypropylene (PP) composites and to investigate the spatial distribution of CNCs in extruded composite filaments. Three composites were made from two forms of nanocellulose (CNCs from wood pulp and the nanoscale fraction of microcrystalline cellulose), and two of the three composites investigated used maleated PP as a coupling agent. Raman maps based on cellulose and PP bands at 1098 and 1460 cm^-1 respectively and obtained at 1 micron spatial resolution showed that the CNCs were aggregated to various degrees in the PP matrix. Of the three composites analyzed, two showed clear existence of phase-separated regions: Raman images with strong PP and absent cellulose, or vice versa. For the third composite, the situation was slightly improved, but a clear transition interface between the PP-abundant and CNC-abundant regions was observed, indicating that the CNC remained poorly dispersed. The spectroscopic approach to investigating spatial distribution of composite components was helpful in evaluating CNC dispersion in the composite at the microscopic level, which helped explain the relatively modest reinforcement of PP by CNCs.

Citation

Agarwal, Umesh; Sabo, Ronald; Reiner, Richard; Clemons, Craig; Rudie, Alan. 2013. Chapter 1.4: Spatially Resolved Characterization of CNC-Polypropylene composite by Confocal Raman Microscopy. In: Postek, Michael T.; Moon, Robert J.; Rudie, Alan W.; Bilodeau, Michael A., eds. Production and Applications of Cellulose Nanomaterials. Peachtree Corners, GA: TAPPI Press. pp. 113-114, Chapter 1.4. ISBN: 978-1-59510-224-9.