Method Development for Contactless Resonant Cavity Dielectric Spectroscopic Studies of Cellulosic Paper

Summary

A protocol for the non-destructive analysis of the fiber content and relative age of paper.

Abstract

The current analytical techniques for characterizing printing and graphic arts substrates are largely ex situ and destructive. This limits the amount of data that can be obtained from an individual sample and renders it difficult to produce statistically relevant data for unique and rare materials. Resonant cavity dielectric spectroscopy is a non-destructive, contactless technique which can simultaneously interrogate both sides of a sheeted material and provide measurements which are suitable for statistical interpretations. This offers analysts the ability to quickly discriminate between sheeted materials based on composition and storage history. In this methodology article, we demonstrate how contactless resonant cavity dielectric spectroscopy may be used to differentiate between paper analytes of varying fiber species compositions, to determine the relative age of the paper, and to detect and quantify the amount of post-consumer waste (PCW) recycled fiber content in manufactured office paper.

Introduction

Paper is a sheeted, heterogenous, manufactured product comprised of cellulosic fibers, sizing agents, inorganic fillers, colorants, and water. The cellulose fibers may originate from a variety of plant sources; the raw material is then broken down through a combination of physical and/or chemical treatments to produce a workable pulp consisting primarily of cellulose fibers. The cellulose in the paper product may also be recovered secondary, or recycled fiber¹. The TAPPI Method T 401, "Fiber analysis of paper and paperboard," is currently the state of the art method for identifying fiber types and their ratios present within a paper sample and ....

Protocol

1. Setup of materials

1. Record all manufacturing information provided with the ream of paper (e.g., basis weight, manufacturer's advertised PCW content, and manufacturer’s advertised brightness).
2. Take an average of ten thickness measurements along a sheet from the ream, using a caliper.
3. Identify the machine and cross directions of the sheet (i.e., the machine direction is the long dimension).
4. Using a protractor identify and cut the paper along the desired strip angle between the machine and cross directions.
5. Using a rotary cutter, slice test strips 0.5 cm wide by 8 cm long in the target orientation for t....

Results

Rationale for choosing the 60° strip angle
The cut orientation of the test sample influences the magnitude of the dielectric response, as shown in the graph in Figure 2. In initial experiments, test strips were cut from the orthogonal angles of the sheet, as is standard practice for measuring physical properties in paper science; however, strips cut from non-orthogonal angles along the paper sheet have provided the greatest resolution between paper types, particularly at.......

Discussion

We have shown elsewhere that the presence of lignin content of fibers does significantly alter the dielectric behavior of manufactured papers¹⁵. Speciation is not only important in the QA/QC testing of modern papers but of great interest in the study of historical papers which were predominantly manufactured from non-wood plant sources, such as bamboo, hemp, flax, and papyrus. As shown in Figure 7, our technique can distinguish between non-wood plant sources (100% cot.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
commercially produced colored office paper	Neenah Paper		Purchased from Staples
Q-Lab QUV accelerated weathering chamber	Q-Lab Corporation, Westlake, OH
X-Rite eXact	X-Rite, Inc., Grand Rapids, MI
Agilent N5225A network analyzer	Agilent Technologies, Santa Rosa, CA
WR90 rectangular waveguide	Agilent Technologies, Santa Rosa, CA		R 100 (a = 10.16 mm, b = 22.86 mm, lz =127.0mm)
JMP data analysis software	SAS, Cary, NC