Brightness measurement of cellulosic materials
Tirronen, Ella (2021)
Tirronen, Ella
2021
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Julkaisun pysyvä osoite on
https://urn.fi/URN:NBN:fi:amk-2021060213666
https://urn.fi/URN:NBN:fi:amk-2021060213666
Tiivistelmä
The objective of this bachelor’s thesis was to study which factors influence the brightness measurement of brightness cakes made from microcrystalline cellulose (MCC). The aim was to determine the factors that have the least favorable effect on brightness and find a method that helps to achieve the most easily repeatable and reliable brightness measurement of sheet brightness.
As a material, MCC is quite difficult because it is sensitive to changes in the surrounding conditions. Its temperature resistance is limited, and as a result, MCC is prone to yellowing when exposed to excessively high temperatures. The MCC particle size is relatively small and because of its crystalline structure their bonding strength is weaker than cellulose fibers. This is the possibly reason for the cracking of the cakes. Another problem is that the brightness cakes curl up while they are drying.
In order to avoid the aforementioned problems, the study started with making brightness cakes with a set of variables. The variables were pH, filtration, rolling, compressing, compression pressure and time, and different drying methods including an air-conditioning room, grill and vacuum dryer. The brightness cakes were made from three different MCC raw materials, and three cakes from each type of material were made. Thus, each series included nine brightness cakes.
Of the different drying methods, the best brightness results and the smoothest cakes were achieved with a vacuum dryer. In the air-conditioning room, the brightness cakes darkened and curled. The grill was found to considerably darken the cakes made from one of the raw materials, which is why it was rejected at an early stage. Rolling was found to be a better method than compression and it provided better brightness regardless of whether the drying method was an air-conditioning room or a vacuum dryer.
The best brightness measurement was achieved when the pH was adjusted to slightly acidic conditions and the cakes were rolled and dried in a vacuum dryer. In this study, different pH was not found to have a significant effect on the brightness of the cakes, but a higher pH slowed filtration through the büchner funnel. With rolling and vacuum drying, the cakes differed the least in appearance, making the method most easily repeatable and reliable.
As a material, MCC is quite difficult because it is sensitive to changes in the surrounding conditions. Its temperature resistance is limited, and as a result, MCC is prone to yellowing when exposed to excessively high temperatures. The MCC particle size is relatively small and because of its crystalline structure their bonding strength is weaker than cellulose fibers. This is the possibly reason for the cracking of the cakes. Another problem is that the brightness cakes curl up while they are drying.
In order to avoid the aforementioned problems, the study started with making brightness cakes with a set of variables. The variables were pH, filtration, rolling, compressing, compression pressure and time, and different drying methods including an air-conditioning room, grill and vacuum dryer. The brightness cakes were made from three different MCC raw materials, and three cakes from each type of material were made. Thus, each series included nine brightness cakes.
Of the different drying methods, the best brightness results and the smoothest cakes were achieved with a vacuum dryer. In the air-conditioning room, the brightness cakes darkened and curled. The grill was found to considerably darken the cakes made from one of the raw materials, which is why it was rejected at an early stage. Rolling was found to be a better method than compression and it provided better brightness regardless of whether the drying method was an air-conditioning room or a vacuum dryer.
The best brightness measurement was achieved when the pH was adjusted to slightly acidic conditions and the cakes were rolled and dried in a vacuum dryer. In this study, different pH was not found to have a significant effect on the brightness of the cakes, but a higher pH slowed filtration through the büchner funnel. With rolling and vacuum drying, the cakes differed the least in appearance, making the method most easily repeatable and reliable.