Sustainability 2023 , 15 , 2850
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Table3. Fiber properties.
Wastepaper
Mean Length-Weighted Fibre Length
Macro-Fibrillation Index
Mean Fibre Coarseness
[mg · m − 1 ]
[ μ m]
[%]
Unrefined
Refined
Unrefined
Refined
Unrefined
Refined
994 925
- -
1.11 1.24 0.51 0.50 0.86 1.22 0.82 0.86 0.88 1.06 0.48 0.69
- -
0.16 0.15 0.10 0.09 0.13 0.15 0.11 0.11 0.10 0.15 0.11 0.14
- -
White1.1 White1.2 White1.3 White1.4 Mixed1.5 White2.1 White2.2 Mixed2.3 Mixed2.4 Mixed2.5 Mixed3.1 White3.2
1021 1126
1006 1038
0.65 0.54 0.65 0.86
0.10 0.10 0.10 0.13
979
880 972
1060
960 884 825 985 886
- - - - -
- - - - -
- - - - -
1022
1001
0.75
0.12
When processing paper, the roughness of the material’s surface is a very important parameter since it affects many properties of the material as well as various other char- acteristics of the product such as appearance, aesthetics, and functional value, which are particularly important in the case of sanitary papers. Hence, based on the three-dimensional microscopic analysis of different papers, roughness profiles were prepared. Specifically, profiles were obtained by separating the long-wave components of the surface profile (waviness and shape deviations) with a λ c profile filter. The λ c profile filter determines the transition from roughness to waviness, that is, random or close-to-periodic inequalities. Therefore, the basic roughness parameters (S a andS z ) describe the surface microgeometry and link it to specific profile features (Table 4). In roughness profiles, S a represents the arithmetic mean deviation of the roughness profile along the sampling length, whilst S z represents the maximum roughness (the maximum height of the profile indicates the ab- solute vertical distance between the maximum profile peak height and maximum profile valley depth along the sampling length).
Table4. Structural and optical properties of papers.
Wastepaper
S a
S z
Air permeability
Roughness
Whiteness
[ μ m] [%] Unrefined Refined Unrefined Refined Unrefined Refined Unrefined Refined Unrefined Refined [ μ m] [mL · min − 1 ] [mL/min]
3.15 3.08 3.78 4.03 3.83 3.51 3.57 3.99 3.98 3.72 4.01 3.74
- -
36.77 32.95 41.21 46.70 42.78 40.81 42.87 39.47 36.95 40.74 48.05 45.06
- -
991 315
- -
183 169 288 298 277
- -
66.38 67.24 85.18 83.05 64.11 78.07 74.58 68.39 70.36 56.75 70.70 76.49
- -
White1.1 White1.2 White1.3 White1.4 Mixed1.5 White2.1 White2.2 Mixed2.3 Mixed2.4 Mixed2.5 Mixed3.1 White3.2
3.64 3.40 3.12 3.00
41.56 45.56 38.87 30.85
4956 3971 2905 2643 4407 4456 3440 1458 5009 4019
2154 1913 1508 1459
252 299 247 274
91.14 80.43 65.89 76.70
60
- - - - -
- - - - -
- - - - -
303
- - - - -
- - - - -
56 59 59
323 319
2.37
32.41
797
189
78.44
Microscopic analysis of paper roughness showed no significant differences depending on the type of wastepaper used to produce paper sheets, despite the differences in the amount of impurities between white and mixed wastepaper (Table 4). Additional roughness measurements, performed following the Bendtsen procedure (Table 4), confirmed that the type of wastepaper used did not alter roughness parameters. Notably, in most cases, the process of refining smoothed the surface of the papers produced only to a small extent.
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