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PEER-REVIEWED ARTICLE
3.10
3.05
3.00
2.95
2.90
2.85
2.80
2.75
2.70
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8
The ratio of fines to FACS
Fig. 4. Effect of the ratio of fines to FACS on paper bulk The tensile strength of paper is influenced by hydrogen bonding. Compared with fibers, fines have a larger surface area and more surface hydroxyl groups per unit mass, which favors the formation of hydrogen bonds. Thus, fines can be regarded as strengthening agents (Xu and Pelton 2005). On the other hand, the composites have larger sized particles than FACS aggregates, as shown in Fig. 3, which helps to decrease the number of particles at the same filler content. Hence, the inter-fiber bonding is affected to a lesser extent. This explains why the paper tensile index increased when fines increased. Fiber average length and hydrogen bonding are critical for tear strength (Liu et al. 2012). Hydrogen bonding and fiber average length are two contradictory parameters with the ratio increase. When the amount of fines increased, the hydroxyl bonding increased and the average length of fibers decreased. Hence, there should be an equilibrium ratio at which the tear strength reaches its maximum. In this work, that ratio is 0.3.
11.2
50
11.0
48
10.8
46
10.6
44
10.4
42
10.2
10.0
40
9.8
38
9.6
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 36
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8
The ratio of fines to FACS The ratio of fines to FACS Fig. 5. Effect of the ratio of fines to FACS on paper tensile and tear strengths To confirm the formation of filler-fines composites in paper, the paper morphology was observed by SEM. As shown in Fig. 6, the fines were coated on the surface of the FACS, playing the role of a bridge linking the FACS and fibers, which mitigated the destruction of hydrogen bonds between fibers.
7411
Zhang et al . (2016 ). “ Coflocculated fines & CaSiO 4 ,” B io R esources 11(3), 7406-7415.
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