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Characterization of dielectric properties and moisture uptake of cellulose nanocrystals using non-contact microwave cavity

Published

Author(s)

Jan Obrzut, Caglar Dogu Emiroglu, Beatriz A. Pazmino, Jack F. Douglas, Jeffrey W. Gilman

Abstract

Dielectric permittivity of cellulose nanocrystals (CNCs) films was determined using a non-contact resonant cavity perturbation method at 7.3 GHz in quantitative correlation with moisture content. The resonant microwave cavity measurement is sensitive to the dielectric permittivity and conductivity. It allows characterization with high speed, precision and efficiency while preserving the morphological integrity of the material, compared to measurements where electrical contacts must be defined and applied in multiple processing steps. Sample films about 100 micrometers thick were obtained from 8% aqueous suspension of CNCs, approximately 5 nm in diameter and 150-200 nm long. The dielectric constant of well dried CNCs is about 3.2 and the corresponding dielectric loss factor is about 0.03. With increasing moisture content both the dielectric constant and the dielectric loss increase considerably. Moisture is strongly bound to cellulose nanocrystals. The effective dielectric constant of water in CNCs, eps'(H2O), is about 30, much smaller than the relaxed static dielectric constant value of unbound water, which is about 78. The strongest interaction is indicated by a minimum value of eps'(H2O) of 30 at moisture content of about 2.5 %. Moisture accelerates the primary relaxation of cellulose nanocrystals by shifting it to higher frequencies.
Proceedings Title
2016 International Conference on Nanotechnology and Renewable Materials
Volume
2016
Conference Dates
June 13-16, 2016
Conference Location
Grenoble

Keywords

Cellulose nano-crystals, moisture uptake, dielectric constant, microwave cavity, non-contact measurements

Citation

Obrzut, J. , , C. , Pazmino, B. , Douglas, J. and Gilman, J. (2016), Characterization of dielectric properties and moisture uptake of cellulose nanocrystals using non-contact microwave cavity, 2016 International Conference on Nanotechnology and Renewable Materials, Grenoble, -1 (Accessed April 23, 2024)
Created September 1, 2016, Updated February 19, 2017