Dielectric spectroscopic studies of biological material evolution and application to paper, TAPPI JOURNAL September 2018

Abstract

Current product composition and quality test methods for the paper and pulp industry are mainly based on manual ex-situ wet-bench chemistry techniques. For example, the standard method for determining the furnish of paper, TAPPI T 401 “Fiber analysis of paper and paperboard,” relies on the experience and visual acuity of a specially trained analyst to determine the individual plant species present and to quantify the amount of each constituent fiber type in a sheet of paper. Thus, there is a need for a fast, nondestructive analytical technique that leverages intrinsic attributes of the analytes. In this paper, we demonstrate an application of dielectric spectroscopy (DS) as a potential metrology to differentiate between nonwood pulp and wood pulp fibers. This in-situ, noncontact and nondestructive assessment method has inherent forensic capabilities and is also amiable to quality assurance techniques such as gauge capability studies and real-time statistical process control (SPC). Application: The dielectric spectroscopy results presented in this paper can nondestructively determine the amount of lignin in paper products and are in principle comparable to the performance specifications of the TAPPI Standard Test Method T 401 and should enable the sources of printing substrates to be both authenticated and validated in real time in a paper testing laboratory environment.

Contactless Resonant Cavity Dielectric Spectroscopic Studies of Cellulosic Paper Aging

“…The ability to differentiate between paper manufactured exclusively from virgin fiber from one that contains only 70% virgin fiber after artificial aging is consistent with our previous work on speciation on the basis of lignin content (Kombolias et al 2018). The broader distribution of the dielectric loss (ε′′ values in the sample with 30% recycled content in Figure 2 suggests that there is greater variability present in the materials tested.…”

“…Inspection of Figure 1 shows that the dielectric loss of the pure cotton and the cotton blend bond paper are different, with lower dielectric loss values for the pure cotton paper samples. The difference may be attributed to the impact of lignin on the distribution of sorbed water in the blended papers (Atalla et al 2000;Arnold 2003;Kombolias et al 2018).…”

“…At least in theory, we should be able to differentiate between samples containing different amounts of degradation products using the resonant cavity technique (Joshi et al 2015). We recently demonstrated the application of contactless resonant cavity dielectric spectroscopy in the testing of paper by leveraging the relaxation dynamics of water molecules adsorbed within the cellulose polymer matrix in the paper analytes as indicators (Kombolias et al 2018). Specifically, we correlated reduction in the rate of depolarization of sorbed water molecules in paper with the fiber species content of a variety of papers.…”

Broadband Microwave Signal Dissipation in Nanostructured Copper Oxide at Air‐film Interface**

“…We suggest that non-contact BDS may be a better metrology for such a sensing application [31]. We have independently investigated and characterized cellulosic paper [32,33], which, when combined with metal oxides, could be suitable for costeffective microwave monitored gas sensing applications. From our experience, the paper substrate for metal oxide support must be carefully chosen for BDS monitoring.…”

Contactless Resonant Cavity Dielectric Spectroscopic Studies of Recycled Office Papers

“…TAPPI Method T 401, "Fiber analysis of paper and paperboard", is the state-of-the-art method for characterizing the fiber types and their ratios in paper samples [1]. Unfortunately, this method does not provide for a means to determine the presence or amount of secondary (i.e., recycled) fiber in paper samples, as virgin and recycled fibers are indistinguishable to the human eye.…”