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Experimental studies on creping and its influence on mechanical properties of tissue paper products

University of British Columbia

Tissue papers are softer, stretchier, and more water absorbent than regular writing or packaging paper products. Creping of an adhesively bonded low-density paper web from the surface of a rotating Yankee drum is the key manufacturing technique in tissue production. Creping dedensifies and weakens the paper by partially damaging the fibers and the inter-fiber bonds in the fiber network. The process also imparts a signature microstructure, called crepe structure, to the tissue paper. Tissues thus produced have a high specific volume (bulk to basis weight ratio), work to rupture, failure strain (stretch), softness and absorbency. Mechanical properties of tissues are governed by the creping process. Therefore, a scientific understanding of the creping process, and its impact on the structural and mechanical properties of the tissue paper is important. The present research approaches the highly complex problem from an experimental perspective, with a view to complement ongoing physics based numerical models to simulate creping. Experimental techniques are developed to visualize the high speed creping process, quantify the crepe structure, and finally understand the influence of the crepe structure on the uni-axial tensile response of the tissue. A novel surface imaging based structural quantification technique is developed and successfully demonstrated on a commercial tissue machine. The surface image based quantification technique is also validated by micrographic observations of the tissue cross section under a Scanning Electron Microscope (SEM). This work lays the foundational techniques and protocols for future studies in the laboratory and opens the opportunity to observe crepe structure in real time for quality and process control. The surface imaging techniques are then used to observe the evolution of the creping microstructure under a tensile load. Local two dimensional strain fields are quantified using Digital Image Correlation (DIC) to gain insight into failure mechanisms at the macroscopic network level. Micro tensile tests are conducted under SEM to gain further insight into the deformation and failure mechanisms operative at fiber length scales. The studies showed the impact of the creping structure, formation, and inter fiber bonds on the tensile response of the tissue paper, specifically along machine direction.

Text

2019-01-14

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/68243

Mechanical Engineering

University of British Columbia

UBCV

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