Effects of heating, drying and straining on the relaxation and tensile properties of wet paper: Dissertation

Research output: ThesisDissertation

Abstract

Producers, converters and printers of paper try to maximize the production and minimize the waste. The runnability of paper web plays an important role when the efficiency of processes is improved. This investigation was here focused on evaluating in-plane viscoelastic strength properties of paper when miming the conditions typical of the paper machine press and dryer section. In order to study the effects of refining, straining, heating and drying on wet paper strength properties, new test methods were developed. The advantage of these methods was to produce more realistic laboratory data for evaluating the runnability of wet paper web in the paper machine and that of dry paper web in the converting and printing processes. Measurement of the residual tension in a tension relaxation test is essential for describing the runnability of a pulp furnish in the paper machine. In addition to this, several parameters are needed to describe the runnability of wet and dry paper web. The tension-strain behavior of wet paper and web handling in the paper machine determines to large extent the runnability potential of dry paper. Wet web draws during drying influence the tension-strain properties of dry web that govern the dry web runnability. In wood containing printing paper grades (NEWS, LWC, SC) the runnability potential of mechanical pulps (TMP, PGW) is very good compared with that of chemical reinforcement pulps. The effect of addition of bleached softwood reinforcement pulp on the tension-strain properties of mechanical-pulp-based furnish is different for dry and wet paper. Generally, in mechanical-pulp-based furnishes, bleached softwood reinforcement pulp is not able to improve the tensile stiffness of wet paper. However, the reinforcement ability of bleached softwood kraft pulp in wet paper depends on the strength properties of the mechanical pulp there. Heating has a strong negative influence on the strength and relaxation properties of wet paper. Decrease of its tensile stiffness can be explained by softening of polymers in the cell wall of fibers. The observed temperature-accelerated relaxation in wet paper seems to be analogous to the moisture-accelerated creep phenomenon in dry paper. Elevated temperatures used in the paper machine have a strong influence on the wet web tensile behavior, e.g. in the transfer from the press to the dryer section, as the tensile stiffness is decreased and increasing tension relaxation of the wet web. This work raises some fundamental aspects in the complex subject of the paper web runnability, and aim to provide tools for the controlling the wet web tension-strain behavior, and ensuring properties of the end product.
Original languageEnglish
QualificationDoctor Degree
Awarding Institution
  • University of Jyväskylä
Supervisors/Advisors
  • Timonen, Jussi, Supervisor, External person
  • Retulainen, E A , Advisor
Award date10 Dec 2014
Place of PublicationJyväskylä
Publisher
Print ISBNs978-951-39-5866-4
Electronic ISBNs978-951-39-5867-1
Publication statusPublished - 2014
MoE publication typeG5 Doctoral dissertation (article)

Fingerprint

Tensile properties
Mechanical pulp
Drying
Heating
Pulp
Softwoods
Reinforcement
Stiffness
Printing
Kraft pulp
Refining
Wood
Creep
Moisture
Cells
Temperature
Fibers
Polymers

Keywords

  • drying
  • filler content
  • heating
  • jet/wire speed ratio
  • refining
  • relaxation rate
  • residual tension
  • runnability
  • tensile strength
  • tensile stiffness
  • wet paper

Cite this

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title = "Effects of heating, drying and straining on the relaxation and tensile properties of wet paper: Dissertation",
abstract = "Producers, converters and printers of paper try to maximize the production and minimize the waste. The runnability of paper web plays an important role when the efficiency of processes is improved. This investigation was here focused on evaluating in-plane viscoelastic strength properties of paper when miming the conditions typical of the paper machine press and dryer section. In order to study the effects of refining, straining, heating and drying on wet paper strength properties, new test methods were developed. The advantage of these methods was to produce more realistic laboratory data for evaluating the runnability of wet paper web in the paper machine and that of dry paper web in the converting and printing processes. Measurement of the residual tension in a tension relaxation test is essential for describing the runnability of a pulp furnish in the paper machine. In addition to this, several parameters are needed to describe the runnability of wet and dry paper web. The tension-strain behavior of wet paper and web handling in the paper machine determines to large extent the runnability potential of dry paper. Wet web draws during drying influence the tension-strain properties of dry web that govern the dry web runnability. In wood containing printing paper grades (NEWS, LWC, SC) the runnability potential of mechanical pulps (TMP, PGW) is very good compared with that of chemical reinforcement pulps. The effect of addition of bleached softwood reinforcement pulp on the tension-strain properties of mechanical-pulp-based furnish is different for dry and wet paper. Generally, in mechanical-pulp-based furnishes, bleached softwood reinforcement pulp is not able to improve the tensile stiffness of wet paper. However, the reinforcement ability of bleached softwood kraft pulp in wet paper depends on the strength properties of the mechanical pulp there. Heating has a strong negative influence on the strength and relaxation properties of wet paper. Decrease of its tensile stiffness can be explained by softening of polymers in the cell wall of fibers. The observed temperature-accelerated relaxation in wet paper seems to be analogous to the moisture-accelerated creep phenomenon in dry paper. Elevated temperatures used in the paper machine have a strong influence on the wet web tensile behavior, e.g. in the transfer from the press to the dryer section, as the tensile stiffness is decreased and increasing tension relaxation of the wet web. This work raises some fundamental aspects in the complex subject of the paper web runnability, and aim to provide tools for the controlling the wet web tension-strain behavior, and ensuring properties of the end product.",
keywords = "drying, filler content, heating, jet/wire speed ratio, refining, relaxation rate, residual tension, runnability, tensile strength, tensile stiffness, wet paper",
author = "Jarmo Kouko",
note = "BA3152",
year = "2014",
language = "English",
isbn = "978-951-39-5866-4",
series = "University of Jyv{\"a}skyl{\"a}: Department of Physics. Research Report",
publisher = "University of Jyv{\"a}skyl{\"a}",
number = "12",
address = "Finland",
school = "University of Jyv{\"a}skyl{\"a}",

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Effects of heating, drying and straining on the relaxation and tensile properties of wet paper : Dissertation. / Kouko, Jarmo.

Jyväskylä : University of Jyväskylä, 2014. 114 p.

Research output: ThesisDissertation

TY - THES

T1 - Effects of heating, drying and straining on the relaxation and tensile properties of wet paper

T2 - Dissertation

AU - Kouko, Jarmo

N1 - BA3152

PY - 2014

Y1 - 2014

N2 - Producers, converters and printers of paper try to maximize the production and minimize the waste. The runnability of paper web plays an important role when the efficiency of processes is improved. This investigation was here focused on evaluating in-plane viscoelastic strength properties of paper when miming the conditions typical of the paper machine press and dryer section. In order to study the effects of refining, straining, heating and drying on wet paper strength properties, new test methods were developed. The advantage of these methods was to produce more realistic laboratory data for evaluating the runnability of wet paper web in the paper machine and that of dry paper web in the converting and printing processes. Measurement of the residual tension in a tension relaxation test is essential for describing the runnability of a pulp furnish in the paper machine. In addition to this, several parameters are needed to describe the runnability of wet and dry paper web. The tension-strain behavior of wet paper and web handling in the paper machine determines to large extent the runnability potential of dry paper. Wet web draws during drying influence the tension-strain properties of dry web that govern the dry web runnability. In wood containing printing paper grades (NEWS, LWC, SC) the runnability potential of mechanical pulps (TMP, PGW) is very good compared with that of chemical reinforcement pulps. The effect of addition of bleached softwood reinforcement pulp on the tension-strain properties of mechanical-pulp-based furnish is different for dry and wet paper. Generally, in mechanical-pulp-based furnishes, bleached softwood reinforcement pulp is not able to improve the tensile stiffness of wet paper. However, the reinforcement ability of bleached softwood kraft pulp in wet paper depends on the strength properties of the mechanical pulp there. Heating has a strong negative influence on the strength and relaxation properties of wet paper. Decrease of its tensile stiffness can be explained by softening of polymers in the cell wall of fibers. The observed temperature-accelerated relaxation in wet paper seems to be analogous to the moisture-accelerated creep phenomenon in dry paper. Elevated temperatures used in the paper machine have a strong influence on the wet web tensile behavior, e.g. in the transfer from the press to the dryer section, as the tensile stiffness is decreased and increasing tension relaxation of the wet web. This work raises some fundamental aspects in the complex subject of the paper web runnability, and aim to provide tools for the controlling the wet web tension-strain behavior, and ensuring properties of the end product.

AB - Producers, converters and printers of paper try to maximize the production and minimize the waste. The runnability of paper web plays an important role when the efficiency of processes is improved. This investigation was here focused on evaluating in-plane viscoelastic strength properties of paper when miming the conditions typical of the paper machine press and dryer section. In order to study the effects of refining, straining, heating and drying on wet paper strength properties, new test methods were developed. The advantage of these methods was to produce more realistic laboratory data for evaluating the runnability of wet paper web in the paper machine and that of dry paper web in the converting and printing processes. Measurement of the residual tension in a tension relaxation test is essential for describing the runnability of a pulp furnish in the paper machine. In addition to this, several parameters are needed to describe the runnability of wet and dry paper web. The tension-strain behavior of wet paper and web handling in the paper machine determines to large extent the runnability potential of dry paper. Wet web draws during drying influence the tension-strain properties of dry web that govern the dry web runnability. In wood containing printing paper grades (NEWS, LWC, SC) the runnability potential of mechanical pulps (TMP, PGW) is very good compared with that of chemical reinforcement pulps. The effect of addition of bleached softwood reinforcement pulp on the tension-strain properties of mechanical-pulp-based furnish is different for dry and wet paper. Generally, in mechanical-pulp-based furnishes, bleached softwood reinforcement pulp is not able to improve the tensile stiffness of wet paper. However, the reinforcement ability of bleached softwood kraft pulp in wet paper depends on the strength properties of the mechanical pulp there. Heating has a strong negative influence on the strength and relaxation properties of wet paper. Decrease of its tensile stiffness can be explained by softening of polymers in the cell wall of fibers. The observed temperature-accelerated relaxation in wet paper seems to be analogous to the moisture-accelerated creep phenomenon in dry paper. Elevated temperatures used in the paper machine have a strong influence on the wet web tensile behavior, e.g. in the transfer from the press to the dryer section, as the tensile stiffness is decreased and increasing tension relaxation of the wet web. This work raises some fundamental aspects in the complex subject of the paper web runnability, and aim to provide tools for the controlling the wet web tension-strain behavior, and ensuring properties of the end product.

KW - drying

KW - filler content

KW - heating

KW - jet/wire speed ratio

KW - refining

KW - relaxation rate

KW - residual tension

KW - runnability

KW - tensile strength

KW - tensile stiffness

KW - wet paper

M3 - Dissertation

SN - 978-951-39-5866-4

T3 - University of Jyväskylä: Department of Physics. Research Report

PB - University of Jyväskylä

CY - Jyväskylä

ER -