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Surface Science of Paper
Professors Doug Reeve and Ramin Farnood
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Surface characteristics of paper play a vitally
important role in controlling paper and print quality. Today’s
paper products must be designed with optimum surface properties
to meet increasingly strict performance criteria in a rapidly changing
market. However, many of the tools presently available for print
quality evaluation and optimization are subjective and often unreliable.
The objective of the consortium is to use leading-edge techniques
to examine and exploit surface phenomena strategically important
to paper manufacture and use, with the ultimate goal of contributing
to the development of new and improved paper products.
Our program stands firmly on the shoulders of four years of focussed
research effort in the area of paper surface science at the University
of Toronto. The present consortium, “Surface Science for Superior
Paper in the Digital Era”, is sponsored by six companies from
Canada, the United States, and Japan, with nine participating faculty.
The research is organized into three subareas: Paper Surface Structure;
Coating and Calendering Processes; and Printing Fundamentals. Our
team brings to bear the unique capabilities of a major research
university in its investigation of fundamental and emerging issues
in paper science.
Our research program has already received supplementary funding
of $122,000/year for four years from the government of Canada. A
second application for additional funding from the federal government
is being prepared and will be submitted shortly.
Currently, there are twelve projects underway which address a number
of issues, including the surface structure of paper and its evolution
in calendering, coating, and printing, and chemical distribution
from the nano- to the micro-scale. We are looking at a wide range
of paper and board grades, from uncoated to coated, and we have
the capability to analyze substrates through each of the stages
of paper production: fibre processing, papermaking, coating, and
printing. We believe that this approach will provide rigorous data
and analysis which will serve as a foundation for commercial innovation.
Over the past eighteen months, we have made significant progress
in our research program. In particular, we have developed analytical
techniques for interrogating the in-plane and z-direction structure
and chemical distribution using time of flight secondary mass spectrometry
(ToFSIMS), atomic force microscopy, and micro-thermal analysis.
Cross section of a coated paper sample using ToFSIMS (500
x 500 µm)
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Topography map of the cross section of a single pass, one
side lab coated paper by Atomic Force Microscopy using contact
mode (100 x 100 µm2)
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In addition, a custom-made setup has been put
in place to assess the microgloss uniformity of paper and prints
and its relationship to the surface structure of paper. The gray
level variation of the microgloss map represents the microgloss
nonuniformity. We found that the root mean square roughness and
the correlation length of surface topography together control the
uniformity of microgloss.
A 1 x 1 cm microgloss map of a highgloss
coated sample |
A 460 x 604 µm optical profilometry
image of the same sample
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We have also developed a novel laboratory apparatus
to simulate the misting tendency of coating formulations at speeds
comparable to those of commercial coaters, an FTIR micro-spectroscopy
method for analyzing coating weight nonuniformity, and a theoretical
model for soft-nip calendering of coated papers.
Contact:
Professor Ramin Farnood at:
Phone: (416) 946-7525
Fax: (416) 971-2106
Email: farnood @ chem-eng.utoronto.ca
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Chemical
Surface
Science