The thesis has been carried out as a part of the Master of Science in mechanical engineering at Karlstads University. The purpose of the study was to evaluate how different variables affect the tearing resistance in a multi-ply paperboard. The paperboard’s final quality is dependent on several different process – and recipe variables and has, in this study, been analyzed with respect to ply grammage, ply composition and refining energies. This was investigated by manufacturing of anisotropic sheets consisting of four plies and isotropic sheets consisting of single-ply sheets. The multi-ply sheets were manufactured where one variable at a time were tested at different values. The single-ply sheets were manufactured of pure pulps with the refining energy being varied. A total of nineteen unique multi-ply sheets and twelve unique single-ply sheets were manufactured. All sheets were tested with respect to the properties including tensile strength, bending stiffness, tear strength and delamination strength. The study shows that an improvement in tearing resistance is obtained when the amount of CTMP-pulp in the center plies 2 and 3 decreases simultaneously as the amount of broke-pulp and unbleached chemical pulp in the same plies increases. The consequence of this improvement is reduced thickness and thereby reduced bending stiffness. The study also shows that several pulps has an optimal degree of refining for maximizing tear strength in paperboard. The major source of error is believed to be the method of manufacturing. It is also possible that the amount of test points has been too few to be able to see any clear trends for several variables.
| Identifer | oai:union.ndltd.org:UPSALLA1/oai:DiVA.org:kau-62638 |
| Date | January 2017 |
| Creators | Erhage, Sofie |
| Publisher | Karlstads universitet |
| Source Sets | DiVA Archive at Upsalla University |
| Language | English |
| Detected Language | English |
| Type | Student thesis, info:eu-repo/semantics/bachelorThesis, text |
| Format | application/pdf |
| Rights | info:eu-repo/semantics/openAccess |
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