Appl. Sci. 2025 , 15 , 875
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Table3. Tensile properties of paper from 3.2 white wastepaper.
E w
W
W
b
b
E b
Retention Agent Addition I B
F B
E*
W
W T
ε
σ
σ T
T
T
T
[J/m 2 ]
[%] Ref.
[m]
[N]
[N/m] [Nm/g]
[%] 2.53 2.37 1.42 1.35 1.23 1.33 1.67 1.97 2.13
[J/g]
[N/m] [Nm/g] [MPa]
3750 3200 2600 2450 2450 2450 2600 2600 3050
42.6 36.6 29.3 27.6 27.7 27.8 29.4 29.7 34.8
2932 2524 2018 1899 1907 1912 2022 2048 2395
36.2 31.2 24.9 23.4 23.5 23.6 25.0 25.3 29.6
54.2 46.0 21.2 17.9 18.3 16.4 27.2 30.0 37.7
0.669 408,133 5040 0.568 383,817 4740 0.262 376,967 4655 0.221 373,000 4606 0.226 372,867 4604 0.203 365,733 4516 0.336 356,433 4401 0.371 354,900 4383 0.466 347,217 4288
3662 3444 3382 3346 3345 3281 3198 3184 3115
0.1 0.2 0.3 0.4 0.5 0.6 0.8 1.0
For the 1.3 wastepaper, the reference sample exhibited the highest tensile strength values, with a breaking length of 2700 m. The addition of the retention aid resulted in an initial decrease in these values. At an addition rate of 0.2%, the breaking length dropped to 1800 m (a 33% reduction) and the force-at-break index decreased to 17.9 Nm/g (a 32% reduction). Further increasing the retention agent to 0.3% and 0.4% caused slight variations, but no significant improvement was observed. Interestingly, at concentrations above 0.8%, a reverse trend emerged, with strength values starting to recover. At 1.0% addition, the breaking length increased to 2150 m, and the force-at-break index reached 21.2 Nm/g. Despite this recovery, these values still did not exceed those of the reference sample. Other mechanical properties followed a similar trend. Strain at break decreased significantly at lower dosages, from 1.60% in the reference to 0.92% at 0.2%. However, it improved to 1.40% at 1.0%. The energy absorption index showed a marked drop at lower dosages but recovered to 0.194 J/g at 1.0%. The 3.2 wastepaper exhibited higher initial tensile properties compared to 1.3, likely due to differences in pulp composition and the heterogeneity of wastepaper. The reference sample had a breaking length of 3750 m, a breaking force of 42.6 N, and a tensile index of 36.2 Nm/g. However, the addition of the retention agent followed a similar decreasing trend. At 0.2% addition, the breaking length reduced to 2600 m (a 31% reduction), and the force-at-break index decreased to 24.9 Nm/g (a 31% reduction). As with the 1.3 type of wastepaper, increasing the retention agent concentration to 0.8% and 1.0% reversed the trend, with the force-at-break index reaching 29.6 Nm/g at 1.0%. Despite this recovery, the values remained lower than those of the reference. The strain at break and work of fracture also exhibited comparable trends. At 0.2%, the strain at break dropped sharply to 1.42% but improved to 2.13% at 1.0%. Similarly, the energy absorption index decreased to 0.262 J/g at 0.2% but recovered to 0.466 J/g at 1.0%. The results indicate a non-linear relationship between retention agent dosage and tensile properties, with an optimal range where the balance between fiber retention and bonding strength is achieved. Both wastepaper types exhibited a notable decline in tensile properties at lower concentrations of the retention agent (0.2–0.6%), with an average reduction in breaking length of 36% for 1.3 and 31% for 3.2. This reduction can be attributed to the over-dosage of the cationic polyelectrolyte, which may lead to flocculation and uneven fiber distribution, weakening the paper’s structure, which aligns with the findings from other studies, underscoring the importance of optimizing retention agent levels to achieve desired mechanical performance without compromising structural uniformity. Interestingly, at higher concentrations (0.8–1.0%), the tensile properties showed recovery. This suggests that the retention aid’s ability to enhance fiber bonding overcomes its adverse effects at higher dosages, although the recovered values did not surpass the reference.
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