Daisy A Sriwendari, Edwin K Sijabat / JBAT 9 (2) (2020) 126-134
crystallinity degree is quite high at 60-80% and the mechanical strength is high and the elasticity modulus is high (Jonas & Farah, 1998).
Bursting Test and Ply Bonding Results
Figures 5 and 6 show that the bursting index and ply bonding values are increasing, from the hand sheet blanko to the hand sheet trial 6, both in the experiment without the surface sizing coating, and in the experiment with surface sizing coating.
Figure 3. The ring crush index result.
Figure 5. Bursting index test result.
Figure 4. The concora test index.
Therefore, the ring crush index and concora trial index values obtained are higher, compared to ring crush index and concora index blanko. Thus the use of BNC in trial proved to increase the handsheet strength properties, compared to the use of additives (PAC and cationic retention) in blanko. Surface sizing is the application of adhesive material (size) on the surface of the paper that has been formed. The main objectives of surface sizing are to obtain paper that is resistant to liquid penetration, to increase the paper surface resistance to chemical absorption, and to increase the physical characteristics of the paper such as its resistance from cracking, cracking, pulling, and folding. Thus the resulting ring crush index and concora index with surface sizing coating are better compared to those without surface sizing coating both in blanko using surface sizing agent as well in trial using BNC to replace the surface sizing agent. The increasing ring crush index and concora index are also influenced by coat weight of the sizing. The heavier the coat weight will increase the ring crush index and concora index, and vice versa.
Figure 6. Ply bonding test result.
The increase in the paper bursting index and ply 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). This is because the high number of free hydroxyl groups produce extensive intra and intermolecular hydrogen bonds between adjacent chains (Brown, 1985). Microbial cellulose has several advantages including high degree of crystallinity, has a density between 300 and 900 kg m-3 and is elastic (Krystynowicz & Bielecki, 2001). The use of BNC can also fill the space between fibers. This advantage causes the bursting index and ply bonding values to increase. The highest bursting index and ply bonding value are in the trial handsheet 6, with the BNC composition at 30%. This shows that using BNC can increase internal strength between fiber layers. Thus using BNC in the trial proved to increase the strength properties handsheet, compared to using
130
Made with FlippingBook Ebook Creator