Contactless Resonant Cavity Dielectric Spectroscopic Studies of Recycled Office Papers

Abstract

Current product composition and quality test methods for the paper and pulp industries are rooted in wet-bench chemistry techniques which cannot be used to distinguish between virgin and secondary fibers. We have recently demonstrated the application of an in situ and nondestructive assessment method based on dielectric spectroscopy (DS), which can address this deficiency in the testing of paper. The DS technique, which employs a resonant microwave cavity, could be applicable to quality assurance techniques such as gauge capability studies and real-time statistical process control (SPC), and may have inherent forensic capabilities. In this paper, we show how this DS technique can be used to distinguish between office copier paper products which may contain recycled fibers. We show a reasonable correlation between the dielectric characteristics (e.g., dielectric loss) and the atomistic level chemical changes that result from the paper recycling process.

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

“…In the modern era, cotton is the most common nonwood fiber used in papermaking for secure and nonsecure high-value printing papers. Cotton fiber is easily distinguishable from wood fiber via optical microscopy by its dimensions, morphology, as well as its reaction to iodine-based stains, such as Graff’s C-Stain [12,13,15]. However, the quantitative determination of cotton content in paper is still a lengthy and onerous task if one relies upon an optical microscope and the TAPPI T 401 procedure.…”

“…While there is a significant body of work that uses DS techniques to study cellulose, wood, pulp, and paper, these studies have typically been focused on moisture content determination in the prediction of the mechanical properties based upon the dielectric anisotropy [7–12]. In this paper, we demonstrate the application of DS to test paper beyond moisture and mechanical properties to distinguish and understand the relationships between the various types of fiber present in an analyte [13]. This in-situ, nondestructive assessment method is also amiable to quality assurance techniques such as gauge capability studies and real-time statistical process control (SPC).…”