Daisy A Sriwendari, Edwin K Sijabat / JBAT 9 (2) (2020) 126-134
cellulose α content is higher, which is around 70% and the remaining 30% is β cellulose. Whereas in bacterial cellulose, the β cellulose content is higher at 60%. The density of cellulose α is bigger than that of cellulose β , hence the density of bacterial cellulose is smaller than that of wood cellulose (Sugiyama et al., 1991). This bacterial cellulose has a diameter of about 2-20 nm and a length of 100 - 40,000 nm. The cellulose produced is stronger, thinner, and lighter than the cellulose that comes from plants (Stanley et al., 2006). The porosity is also very low with a diameter of 70-80nm, the degree of crystallinity is quite high, namely 60-80% and has large mechanical strength and high modulus of elasticity (Jonas & Farah, 1998). Therefore it can make the difference in fiber weight between bacterial cellulose and wood cellulose.
Drainage Speed Test Results
Figure 1 shows the slowing down of drainage, that is the water takes longer time to get out of the stock. This happens along with the addition of BNC composition into the stock.
Figure 1. Drainage test result.
This is because BNC is hydrophilic and the fiber structure is in gel fom and very small, about 2- 20 nm in diameter and 100 - 40,000 nm in length. The non-branched glucose chains make long fibril structures. The high number of free hydroxyl groups produce extensive intra and intermolecular hydrogen bonds between adjacent chains (Brown, 1985). These very small and nano-sized fibers make the braids really strong and tight that even water will struggle to penetrate it. Therefore, the addition of BNC composition into stock must be limited. In this experiment, the maximum BNC composition used was 30% in stock. According to Sijabat et al. (2017), the maximum composition of nanocellulose is 30%, the addition of nanocellulose above 30% can reduce drainage speed and cause problems in the dewatering process. Based on the experimental result, at the trial 6 drainage stock headbox is very slow at 45.16 s/500 ml, because the BNC composition used is at 30%.
Figure 2. Basis weight test result.
Ring Crush and Concora Tests Result
Figures 3 and 4 show that the ring crush index and concora index are increasing, from the hand sheet blank to the hand sheet trial 6, both in the experiment without surface sizing and in the experiment with surface sizing coating. The increase in the paper ring crush index and concora index values is caused by the increasing BNC composition used from the hand sheet blanko (0% BNC) to the hand sheet trial 6 (30% BNC). According to Wiley (2014), Nanocellulose has a low density (1.6 g.cm-3), and the surface of the -OH group is more reactive than cellulose in general. This is because the high number of free hydroxyl groups produce extensive intra and intermolecular hydrogen bonds between adjacent chains (Brown, 1985). Therefore the nano-sized BNC has a vast surface area, with many highly reactive OH groups that can bind easily and establish very strong fiber bonds. The porosity is also very low at 70-80nm in diameter, the
Basis Weight Test Results
Figure 2 shows that the basis weight value is decreasing from the hand sheet blanko to the hand sheet trial 6. The paper basis weight value depends on the paper sheet weight. The paper sheet weight is influenced by the amount and type of pulp given. The decrease in weight base value is caused by the increasing BNC composition used, from the hand sheet blanko to the hand sheet trial 6. In general, cellulose consists of α cellulose and β cellulose. Wood cellulose and bacterial cellulose consist of both cellulose, only with different compositions. In wood cellulose, the
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