This candidate thesis reports the findings of a study on an objective method for measuring grip stiffness in carton board packages with different geometries and material properties. Syntouch Biotac and a tensile tester were used as an objective method for measuring grip stiffness. In this project tests were carried out on packages with three different grammages and two different geometries. For each grammage and geometry, ten packages were tested. The study identifies that the applied method for the measurement of grip stiffness works to measure the change in grip stiffness regardless of where a load was applied on a package. Furthermore, the method demonstrates reasonable results. Finally, the study concluded that the objective testing method could distinguish between different material properties and geometries of the cartons being measured. / En studie om en objektiv metod för mätning av greppstyvhet hos kartongförpackningar med olika geometrier och materialegenskaper rapporteras här. Syntouch Biotac och en provdragare användes som objektiv metod för mätning av greppstyvhet. I detta projekt utfördes tester på förpackningar med tre olika materialegenskaper (ytvikter) samt två olika geometrier. För varje ytvikt och geometri testades tio förpackningar. Studien visar att den maskinbaserade metoden för mätning av greppstyvhet fungerar för att mäta förändring i greppstyvhet oberoende av på var tryck appliceras på förpackningen. Dessutom påvisade studien rimliga resultat. I studien kom författarna även fram till att den maskinbaserade metoden kan skilja olika materialegenskaper och geometrier åt, vilket är verifierar metoden.

The need for sustainable packaging is growing, and plastic waste needs to be reduced. A suitable alternative could be fibre-based packaging and cartonboard, and several actions could enhance this alternative. This study investigates crosslinking, a method to create stronger bonds between the OH-groups in the material. The aim is to gather information on the potential of the concept since there is previously a limited amount of research on the specific area. The goal, in the long run, is to create stronger packaging. The study will contribute with knowledge around how crosslinking can be used to enhance the strength of cartonboard and contribute to the development of more durable material. Two research questions were formulated to investigate this.  RQ1: How does the crosslinking concept affect properties of cartonboard when applied? RQ2: What effect could the crosslinking concept have on the product area cartonboard? The research has a deductive starting point, and the project planning was agile, which allowed the study to form as the results gave new intel about the concept. The focus is on collecting qualitative data with high validity, which has been done by testing the material according to different standards. The material investigated is a folding boxboard (FBB) in four separate grammages to give an overview of the effect of the concepts. Properties evaluated include short span compression test (SCT), tensile strength, recyclability, cobb and box compression resistance tests (BCR), and more.  The results show a slight increase in SCT for the highest, 460 gsm, and lowest, 245 gsm, grammages of the materials used in this study. The recyclable is affected minimally with only a few per cent, but it remains high. However, the material becomes a bit stiffer and suffers losses in tensile strength, elongation, and tensile energy absorption. The enhanced strength seen in SCT does not show for BCR. The crosslinked material tends to crack in the creases before and after bending, especially in the highest grammage. The Cobb results indicate crosslinking shows potential to be used as a barrier to make the material more water repellent.  Conclusions drawn from the results are that even though the SCT value is enhanced for two grammages, it suffers losses in tensile strength, and the strength enhancement does not show for BCR. Therefore, the impact on the product area is not clear, and further research is recommended to understand the area more.  Suggestion for further research is to do more research in the area in general and then scale up the study to a pilot study. This would gain intel on how the concept will work in a non-laboratory situation and investigate how it could be implemented in production

Tryckflammighet, ojämnheter på tryckta ytor är en icke önskvärd egenskap som länge bekymrat tryckeribranschen. Ojämnheterna har medfört en försämrad kvalité på kartongmaterial som visuellt får materialet att se fläckig och sämre ut. Egenskapen har visat sig vara mer tydlig på ytor som tryckts med färgen cyan, vanligt förekommande i metoderna flexotryck och offsettryck. Detta examensarbete har gjorts hos ett företag inom tryckeribranschen. Företaget har använt två metoder för bedömning av tryckflammighet på tryckta vätske- och förpackningskartong, en Parvis visuell bedömning och en instrumentell mätning med en skanner och programvaran STFI Mottling Expert. Programvaran har utvecklats med syftet att på ett identiskt sätt bedöma bland annat tryckflammighet på kartongmaterialytor så som den upplevs på den visuella bedömningen. Under en lång period har företaget använt instrumentet för att verifiera resultat som erhålls från den visuella metoden. Under de senaste åren har korrelationen mellan dessa metoder blivit sämre, till en punkt där företaget inte litar på instrumentet. Korrelationsanalys har därför utförts för att undersöka sambandet mellan dessa två metoder och orsaken till problemet. I samband med detta har företaget upptäckt en möjlighet, att undersöka topografiska egenskaper på otryckt material från samma produktionstillfälle och dess korrelation med tryckflammigheten. Topografiska värden har därför tagits fram via instrumentet L&W OptiTopo samt programvaran RISE OptiTopo Expert och korrelationsanalys utförts. Resultaten indikerar en fortfarande väldigt hög korrelation mellan de två metoder som används för bedömning av tryckflammighet, dock inom andra våglängder än den rekommenderad av programvaran och orsakerna till tidigare problem har lagts fram. Topografiska värden som ytråhet samt andelen kratrar under en viss tröskel har kunnat kopplas till tryckflammighetsvärdet och sambandet visats. / Print mottle, unevenness on printed surfaces is an undesirable property that has long worried the printing industry. The effect has led to a degraded quality in cartonboard which visually makes the material look stained and worse. The property has been shown to be more evident on surfaces printed with the color cyan, commonly in printing methods such as flexography and offset. This project degree has been conducted at a company in the printing industry. The company has used two methods for assessing print mottle on printed liquid- and packaging board, a Pairwise visual assessment and an instrumental measurement with a scanner and software STFI Mottling Expert. The software has been developed with the purpose of identifying among others print mottle on cartonboard surfaces in an identical way as the visual assessment. For a long period of time, the company has used the instrument to verify the results from the visual assessment. In recent years, the correlation between these methods has gotten worse, to a point where company does not trust the instrument. Correlation analysis has therefore been performed to investigate the relationship between these two methods and the cause of the problem. In connection with this, the company has discovered an opportunity, to investigate topographical properties on unprinted materials from the same production line and its correlation with print mottle. Topographical values have therefore been determined using the L&W OptiTopo instrument and RISE OptiTopo Expert software. The results indicate that there is still a very high correlation between the two methods used to assess print mottle, though within wavelengths other than the one recommended by the software and the causes of previous problems have been presented. Topographical values such as surface roughness and the proportion of craters under a certain threshold have been linked to the print mottle value and the correlation between them shown.