Abstract

In paper machine after the wire section the web is wet and weak. In spite of that it is subject to considerable dynamic stresses due to wet pressing, web transfer and drying. As dryness increases also the temperature, structure and mechanical properties of the web are changed. Main changes are related to the reduction of water. Water is located inside the fibre walls and in the pores between fibres. The amount of water contributes to the forces affecting between and within fibres. The properties of wet web are assumed to be affected by the properties of fibres, the interaction forces between fibres and the properties of water used in furnish preparation. Fines have been found to have a considerable effect on mechanical and optical properties of dry paper [1]. It is thus reasonable to expect that fines also modify the behaviour of wet fibre network. In papermaking and converting processes paper is subject also to stresses in out-of plane direction. Typically wet pressing, size pressing, calendering, reeling, winding and printing operations cause considerable dynamic out-of-plane stresses and deformations in paper. Theses processes are dynamic and so the testing method must take place under dynamic conditions. It is important to understand the resulting thickness change, the contact area between paper and the cylinder surface and the final irreversible deformation and how they depend on the shape and extent of the press pulse, and on the temperature - humidity conditions. Paper structure is one factor in determining the compressive deformation of paper. Paper structure is changed by the raw material composition and wet stretching/drying history and material distribution in z-direction.
Original languageEnglish
Place of PublicationEspoo
PublisherVTT Technical Research Centre of Finland
ISBN (Electronic)978-951-38-7201-4
ISBN (Print)978-951-38-7200-1, 978-951-38-7200-7
Publication statusPublished - 2008
MoE publication typeD4 Published development or research report or study

Fingerprint

Rheology
Fibers
Water
Drying
Calendering
Mechanical properties
Papermaking
Stretching
Printing
Atmospheric humidity
Raw materials
Optical properties
Wire
Temperature
Testing
Chemical analysis

Cite this

Retulainen, E., Salminen, K., Ponkkala, T., & Kunnari, V. (2008). Rheology of consolidating fibre network. Espoo: VTT Technical Research Centre of Finland.
Retulainen, Elias ; Salminen, Kristian ; Ponkkala, Tero ; Kunnari, Vesa. / Rheology of consolidating fibre network. Espoo : VTT Technical Research Centre of Finland, 2008.
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Retulainen, E, Salminen, K, Ponkkala, T & Kunnari, V 2008, Rheology of consolidating fibre network. VTT Technical Research Centre of Finland, Espoo.

Rheology of consolidating fibre network. / Retulainen, Elias; Salminen, Kristian; Ponkkala, Tero; Kunnari, Vesa.

Espoo : VTT Technical Research Centre of Finland, 2008.

Research output: Book/ReportReport

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T1 - Rheology of consolidating fibre network

AU - Retulainen, Elias

AU - Salminen, Kristian

AU - Ponkkala, Tero

AU - Kunnari, Vesa

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N2 - In paper machine after the wire section the web is wet and weak. In spite of that it is subject to considerable dynamic stresses due to wet pressing, web transfer and drying. As dryness increases also the temperature, structure and mechanical properties of the web are changed. Main changes are related to the reduction of water. Water is located inside the fibre walls and in the pores between fibres. The amount of water contributes to the forces affecting between and within fibres. The properties of wet web are assumed to be affected by the properties of fibres, the interaction forces between fibres and the properties of water used in furnish preparation. Fines have been found to have a considerable effect on mechanical and optical properties of dry paper [1]. It is thus reasonable to expect that fines also modify the behaviour of wet fibre network. In papermaking and converting processes paper is subject also to stresses in out-of plane direction. Typically wet pressing, size pressing, calendering, reeling, winding and printing operations cause considerable dynamic out-of-plane stresses and deformations in paper. Theses processes are dynamic and so the testing method must take place under dynamic conditions. It is important to understand the resulting thickness change, the contact area between paper and the cylinder surface and the final irreversible deformation and how they depend on the shape and extent of the press pulse, and on the temperature - humidity conditions. Paper structure is one factor in determining the compressive deformation of paper. Paper structure is changed by the raw material composition and wet stretching/drying history and material distribution in z-direction.

AB - In paper machine after the wire section the web is wet and weak. In spite of that it is subject to considerable dynamic stresses due to wet pressing, web transfer and drying. As dryness increases also the temperature, structure and mechanical properties of the web are changed. Main changes are related to the reduction of water. Water is located inside the fibre walls and in the pores between fibres. The amount of water contributes to the forces affecting between and within fibres. The properties of wet web are assumed to be affected by the properties of fibres, the interaction forces between fibres and the properties of water used in furnish preparation. Fines have been found to have a considerable effect on mechanical and optical properties of dry paper [1]. It is thus reasonable to expect that fines also modify the behaviour of wet fibre network. In papermaking and converting processes paper is subject also to stresses in out-of plane direction. Typically wet pressing, size pressing, calendering, reeling, winding and printing operations cause considerable dynamic out-of-plane stresses and deformations in paper. Theses processes are dynamic and so the testing method must take place under dynamic conditions. It is important to understand the resulting thickness change, the contact area between paper and the cylinder surface and the final irreversible deformation and how they depend on the shape and extent of the press pulse, and on the temperature - humidity conditions. Paper structure is one factor in determining the compressive deformation of paper. Paper structure is changed by the raw material composition and wet stretching/drying history and material distribution in z-direction.

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Retulainen E, Salminen K, Ponkkala T, Kunnari V. Rheology of consolidating fibre network. Espoo: VTT Technical Research Centre of Finland, 2008.