Sustainability 2023 , 15 , 2850
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and 3). High tear resistance and elasticity render these papers the most attractive for use in the production of sanitary paper. The lowest strength was recorded from recycled paper1.5, which may be due to the lowest fiber length of its pulp.
Table5. Tensile properties of paper produced from unrefined pulp.
E w
W
W
b
b
E b
Wastepaper
I B
F B
E*
W
W T
ε
σ
σ T
T
T
T
[N · m − 1 ]
[Nm · g − 1 ]
[J · m − 2 ]
[J · g − 1 ] 0.258
[N · m − 1 ] 255,500 266,400 309,100 256,100 258,000 260,600 272,800 216,600 219,900 233,200 261,100
[Nm · g − 1 ]
[m]
[N]
[%] 1.63 1.66 1.69 1.49 1.59 2.06 1.68 1.30 1.53 1.66 1.75 1.70
[MPa]
2500 2900 2850 2300 2300 2450 2550 1800 2050 2250 2350 3150
29.1 34.3 33.1 26.5 26.7 28.3 29.0 20.8 23.6 26.3 28.0 36.6
1956 2319 2220 1829 1804 1924 2012 1412 1590 1760 1892 2480
24.6 28.4 27.7 22.6 22.5 23.8 25.0 16.6 19.9 21.9 23.3 30.5
20.5 25.7 24.0 18.1 19.6 26.7 23.0 10.5 17.0 19.6 21.7 26.2
3213 3262 3859 3157 3159 3224 3391 2678 2756 2900 3207 4031
2320 2425 2809 2328 2344 2367 2481 1970 2000 2120 2376
White1.1 White1.2 White1.3 White1.4 Mixed1.5 White2.1 White2.2 Mixed2.3 Mixed2.4 Mixed2.5 Mixed3.1 White3.2
0.315 0.300 0.224 0.244 0.331 0.285 0.130 0.213 0.244 0.267 0.329
321,400 2922 Abject results are marked with color (the best tensile properties on the green, the worst on the red).
Table6. Tensile properties of paper produced from refined pulps.
E w
W
W
b
b
E b
Wastepaper
I B
F B
E*
W
W T
ε
σ
σ T
T
T
T
[N · m − 1 ]
[Nm · g − 1 ]
[J · m − 2 ]
[J · g − 1 ]
[N · m − 1 ] 514,400 428,700 374,700 378,200 524,100
[Nm · g − 1 ]
[m]
[N]
[%] 3.02 3.16 2,42 2.23 2,52
[MPa]
7050 5150 4050 4400 8100
77.1 59.5 47.5 49.0 93.9
5335 4037 3247 3291
69.0 51.2 40.5 43.0 79.0
103.2
1.33 1.10 0.73 0.70 1.53
4676 3935 3480 3433
White1.3 White1.4 Mixed1.5 White2.1 White3.2
6649 5436 4676 4942 6541
86.9 58.5 53.8
6321 4734 Abject results are marked with color (the best tensile properties on the green, the worst on the red). 123.0
Of note, in a few cases, pulps with similar properties in the unrefined state exhibited markedly different properties in the refined state, such as wastepaper 1.4 and 1.5. Therefore, thorough estimation of the papermaking ability is essential. 4. Conclusions Analyses conducted in the present work were aimed at verifying the specific properties of wastepaper pulp on the basis of which their suitability to produce a product with satisfactory usability characteristics can be initially assessed. However, although the present work does not allow for identifying the pulp that is reliable in terms of papermaking, it allows for revealing the pulp that is not suitable. In other words, the usefulness of recycled pulp can be assessed at high probability by determining the freeness and content of extractive substances. Based on the obtained data, it was conducted that, samples containing large amounts of extractives (above 1.30%) and dissolved substances cannot yield products with a high added value. Also, samples with very high initial Schopper– Riegler freeness should not be introduced into the system, as they do not allow for achieving the expected results and may induce a number of technological difficulties. Similarly, pulp samples with fiber length of <900 μ m do not allow good paper strength, and especially satisfactory tear resistance, so essential to sanitary papers. Moreover, strength properties cannot be determined without the refining process. Overall, comprehensive evaluation of the papermaking ability of wastepaper is imperative. Undeniably, our findings will be helpful to further analyze the validity of recycled materials and reduce the impact of wastepaper on the environment.
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