For this master thesis, two methods to apply a pattern with a controlled amount of moisture to hand sheets were evaluated. The two methods evaluated were spraying and pressing. Spraying moisture onto the sheets was deemed the easiest method to control and was chosen for further studies. The sheets were sprayed with four spray times and patterns to create different moisture content variations (4.2, 8.0, 14.2 and 26.9 pp moisture content difference). The moisture patterns were designed so the sheets had either moist spots with drier surroundings or reversibly, drier spots with moist surroundings. The sprayed sheets were dried unrestrained or fully restrained to study how in-plane moisture variations could affect paper properties and out-of-plane deformation. Unrestrained drying resulted in out-of-plane deformation around the areas where moisture had been applied. Restrained drying resulted in no out-of-plane deformation but instead changes in opacity, permeance, grammage and thickness occurred. The severity of cockling and difference in paper properties after drying were found to increase with greater moisture content variation before drying. However all effects could be obtained even at the lowest moisture content variation. The resulting out-of-plane deformation varied between ±100 μm for 4.2 pp moisture content difference and ±250 μm for 14.2 pp moisture content difference
| Identifer | oai:union.ndltd.org:UPSALLA1/oai:DiVA.org:kth-90433 |
| Date | January 2011 |
| Creators | Tysén, Aron |
| Publisher | KTH, Skolan för kemivetenskap (CHE) |
| 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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