Moisture depth profiling in paper using near-infrared spectroscopy: Dissertation

Research output: ThesisDissertation

Abstract

A near-infrared spectroscopic method and measurement system for moisture depth profiling is presented in this thesis. The measurement system is based on a fibre-optic light source and probes, and a hyperspectral imaging spectrograph. The probes feature six different measurement geometries, including a specular reflection measurement, and diffuse reflection and transmission measurements, all of which are measured in seven positions simultaneously. A theoretical analysis of the depth profiling capabilities of the system is presented, as well as laboratory tests of the system performance. Based on these, the analysis depth of the reflection moisture measurement in a 75 µm thick uncoated paper is estimated to be about 40 µm. It is also shown that the depth profiling properties depend on the average moisture content of the paper, and that the inclusion of a coating layer complicates the depth profiling. The use of the theoretical analysis results in the interpretation of the measurement results is also discussed. As the main application, the measurement system was installed on a pilot-scale paper coating machine. The feasibility of semi-quantitative moisture depth profiling during the coating process is shown. The determination of the first and second critical concentrations of the coating colour consolidation process is also discussed. Detailed results from the extensive programme of trial runs are presented, along with discussion of the physics behind the measurements. It is found that the water transport characteristics measured during the coating process are not in accordance with mass and heat transfer theories in some respects. Also, the specular reflection measurement results do not behave as expected, making the determination of the first critical concentration impossible in some cases. Instead, the second critical concentration is easily detected, but does not always behave as expected. Reasons for the unexpected behaviour of the measurements are discussed, and conclusions drawn about the water transport during the coating process.
Original languageEnglish
QualificationDoctor Degree
Awarding Institution
  • University of Oulu
Supervisors/Advisors
  • Myllylä, Risto, Supervisor, External person
  • Kopola, Harri, Supervisor
Award date14 Dec 2007
Place of PublicationEspoo
Publisher
Print ISBNs978-951-38-7063-8
Electronic ISBNs978-951-38-7064-5
Publication statusPublished - 2007
MoE publication typeG4 Doctoral dissertation (monograph)

Fingerprint

moisture
infrared spectroscopy
coating
specular reflection
coatings
theses
consolidation
light beams
water
moisture content
mass transfer
spectrographs
fiber optics
light sources
heat transfer
inclusions
color

Keywords

  • moisture content
  • depth profiling
  • paper coating
  • optical properties
  • near-infrared spectroscopy
  • NIR
  • fibre-optic light sources
  • fibre-optic probes
  • multichannel spectroscopy
  • water transport characteristics
  • on-line measurement
  • Monte Carlo modelling

Cite this

Paaso, Janne. / Moisture depth profiling in paper using near-infrared spectroscopy : Dissertation. Espoo : VTT Technical Research Centre of Finland, 2007. 204 p.
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title = "Moisture depth profiling in paper using near-infrared spectroscopy: Dissertation",
abstract = "A near-infrared spectroscopic method and measurement system for moisture depth profiling is presented in this thesis. The measurement system is based on a fibre-optic light source and probes, and a hyperspectral imaging spectrograph. The probes feature six different measurement geometries, including a specular reflection measurement, and diffuse reflection and transmission measurements, all of which are measured in seven positions simultaneously. A theoretical analysis of the depth profiling capabilities of the system is presented, as well as laboratory tests of the system performance. Based on these, the analysis depth of the reflection moisture measurement in a 75 µm thick uncoated paper is estimated to be about 40 µm. It is also shown that the depth profiling properties depend on the average moisture content of the paper, and that the inclusion of a coating layer complicates the depth profiling. The use of the theoretical analysis results in the interpretation of the measurement results is also discussed. As the main application, the measurement system was installed on a pilot-scale paper coating machine. The feasibility of semi-quantitative moisture depth profiling during the coating process is shown. The determination of the first and second critical concentrations of the coating colour consolidation process is also discussed. Detailed results from the extensive programme of trial runs are presented, along with discussion of the physics behind the measurements. It is found that the water transport characteristics measured during the coating process are not in accordance with mass and heat transfer theories in some respects. Also, the specular reflection measurement results do not behave as expected, making the determination of the first critical concentration impossible in some cases. Instead, the second critical concentration is easily detected, but does not always behave as expected. Reasons for the unexpected behaviour of the measurements are discussed, and conclusions drawn about the water transport during the coating process.",
keywords = "moisture content, depth profiling, paper coating, optical properties, near-infrared spectroscopy, NIR, fibre-optic light sources, fibre-optic probes, multichannel spectroscopy, water transport characteristics, on-line measurement, Monte Carlo modelling",
author = "Janne Paaso",
note = "Project code: 540",
year = "2007",
language = "English",
isbn = "978-951-38-7063-8",
series = "VTT Publications",
publisher = "VTT Technical Research Centre of Finland",
number = "664",
address = "Finland",
school = "University of Oulu",

}

Moisture depth profiling in paper using near-infrared spectroscopy : Dissertation. / Paaso, Janne.

Espoo : VTT Technical Research Centre of Finland, 2007. 204 p.

Research output: ThesisDissertation

TY - THES

T1 - Moisture depth profiling in paper using near-infrared spectroscopy

T2 - Dissertation

AU - Paaso, Janne

N1 - Project code: 540

PY - 2007

Y1 - 2007

N2 - A near-infrared spectroscopic method and measurement system for moisture depth profiling is presented in this thesis. The measurement system is based on a fibre-optic light source and probes, and a hyperspectral imaging spectrograph. The probes feature six different measurement geometries, including a specular reflection measurement, and diffuse reflection and transmission measurements, all of which are measured in seven positions simultaneously. A theoretical analysis of the depth profiling capabilities of the system is presented, as well as laboratory tests of the system performance. Based on these, the analysis depth of the reflection moisture measurement in a 75 µm thick uncoated paper is estimated to be about 40 µm. It is also shown that the depth profiling properties depend on the average moisture content of the paper, and that the inclusion of a coating layer complicates the depth profiling. The use of the theoretical analysis results in the interpretation of the measurement results is also discussed. As the main application, the measurement system was installed on a pilot-scale paper coating machine. The feasibility of semi-quantitative moisture depth profiling during the coating process is shown. The determination of the first and second critical concentrations of the coating colour consolidation process is also discussed. Detailed results from the extensive programme of trial runs are presented, along with discussion of the physics behind the measurements. It is found that the water transport characteristics measured during the coating process are not in accordance with mass and heat transfer theories in some respects. Also, the specular reflection measurement results do not behave as expected, making the determination of the first critical concentration impossible in some cases. Instead, the second critical concentration is easily detected, but does not always behave as expected. Reasons for the unexpected behaviour of the measurements are discussed, and conclusions drawn about the water transport during the coating process.

AB - A near-infrared spectroscopic method and measurement system for moisture depth profiling is presented in this thesis. The measurement system is based on a fibre-optic light source and probes, and a hyperspectral imaging spectrograph. The probes feature six different measurement geometries, including a specular reflection measurement, and diffuse reflection and transmission measurements, all of which are measured in seven positions simultaneously. A theoretical analysis of the depth profiling capabilities of the system is presented, as well as laboratory tests of the system performance. Based on these, the analysis depth of the reflection moisture measurement in a 75 µm thick uncoated paper is estimated to be about 40 µm. It is also shown that the depth profiling properties depend on the average moisture content of the paper, and that the inclusion of a coating layer complicates the depth profiling. The use of the theoretical analysis results in the interpretation of the measurement results is also discussed. As the main application, the measurement system was installed on a pilot-scale paper coating machine. The feasibility of semi-quantitative moisture depth profiling during the coating process is shown. The determination of the first and second critical concentrations of the coating colour consolidation process is also discussed. Detailed results from the extensive programme of trial runs are presented, along with discussion of the physics behind the measurements. It is found that the water transport characteristics measured during the coating process are not in accordance with mass and heat transfer theories in some respects. Also, the specular reflection measurement results do not behave as expected, making the determination of the first critical concentration impossible in some cases. Instead, the second critical concentration is easily detected, but does not always behave as expected. Reasons for the unexpected behaviour of the measurements are discussed, and conclusions drawn about the water transport during the coating process.

KW - moisture content

KW - depth profiling

KW - paper coating

KW - optical properties

KW - near-infrared spectroscopy

KW - NIR

KW - fibre-optic light sources

KW - fibre-optic probes

KW - multichannel spectroscopy

KW - water transport characteristics

KW - on-line measurement

KW - Monte Carlo modelling

M3 - Dissertation

SN - 978-951-38-7063-8

T3 - VTT Publications

PB - VTT Technical Research Centre of Finland

CY - Espoo

ER -

Paaso J. Moisture depth profiling in paper using near-infrared spectroscopy: Dissertation. Espoo: VTT Technical Research Centre of Finland, 2007. 204 p.