Open Collections

Mohammadi, Omid

University of British Columbia

Press felts are vital components in the papermaking process, serving to remove water from the fiber mat and enhance fiber bonding during pressing. Due to manufacturing and installation limitations, press felts are not continuous but are assembled using seams. These seams can lead to variations in the wet and dry strength of paper compared to areas pressed without seams. This study investigates the impact of press felt seams on the wet strength of paper. An experimental apparatus is developed to apply pressure to the paper using a seamed press felt under tension. Handsheet papers are pressed in this apparatus and subsequently tensile tests are conducted on the paper. Various parameters are examined to cover a broad spectrum of applications in the paper industry, including moisture content, pressure, paper grammage, seam size (gap size), press felt configuration, and press felt tension. The experimental results show that there exists a threshold for seam size above which the tensile index at the seam is equal to that of unpressed paper. The effective seam size of a press felt seam is directly proportional to the applied tension, and press felt tension impacts the seam tensile index through this mechanism. The influence of seam size on paper strength is modulated by fiber length and type (hardwood or softwood). Longer fiber lengths resulted in a higher tensile index at both the seam and the pressed area. Additionally, longer fibers increase the threshold beyond which the seam size no longer significantly affects the results. Additionally, increased moisture content reduces the tensile index of the paper and minimizes the difference in tensile strength between the seam and pressed areas. This strength difference is also more pronounced at higher pressures and paper grammages. Moreover, the thickness of the paper at the seam is greater than that in other pressed regions but less than that of unpressed paper in all cases. The effect of the seam on paper strength is further amplified in a double felt configuration, due to the deformation occurring in the paper at the seam region under this configuration.

Text

2024-10-17

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/89426

Mechanical Engineering

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/