Contactless Resonant Cavity Dielectric Spectroscopic Studies of Recycled Office Papers

Mary Kombolias,Dianne L Poster,Yaw S Obeng,Michael T Postek,Jan Obrzut

doi:10.3390/recycling4040043

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.

Highlights

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]
The dielectric loss appears to increase with increasing secondary fiber content of the paper
The iterative cycles of cleaning and repulping of the reclaimed fibers change the physicochemical nature of the recycled paper product compared to a virgin fiber paper product

Summary

Introduction

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] 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. Indirect techniques, such as the use of Simons’ Stain, to examine the pore capillary structure of sheets and pulps by a size exclusion mechanism may suggest, but not definitively identify, the presence of secondary fiber in a test sample [2,3]. The method has not been widely adopted because its accuracy and reproducibility were too low [7,8]

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Discussion

Conclusion