1910
Journal of Material Cycles and Waste Management (2025) 27:1901–1913
Table 4 Physical properties of handsheets for each pulp in recycle loops with a heavily refined condition
Basis Weight (g/m 2 )
Sheet Density (kg/m 3 )
Cycle
Caliper (μm)
Tensile Index, (N·m/g)
Ring Crush Index (N·m/g)
UBKP
Unrefined
162.83 ± 8.63
468.78 ± 29.46
347.57 ± 6.67
36.59 ± 1.94
8.05 ± 0.22
0
163.37 ± 8.09
305.96 ± 7.93
533.70 ± 12.85
66.91 ± 4.87
15.57 ± 0.93
1
162.94 ± 4.71
328.64 ± 12.23
495.98 ± 8.97
54.70 ± 8.05
12.46 ± 0.31
2
161.46 ± 1.25
338.20 ± 5.57
477.50 ± 7.64
56.33 ± 2.02
11.58 ± 0.30
3
160.55 ± 4.68
324.24 ± 5.09
495.10 ± 8.96
54.34 ± 1.94
11.49 ± 0.67
4
157.89 ± 7.32
320.40 ± 14.55
492.82 ± 7.98
55.33 ± 4.34
11.52 ± 0.44
5
164.20 ± 6.16
320.88 ± 7.51
511.61 ± 8.90
58.77 ± 2.47
12.02 ± 0.58
6
159.91 ± 5.39
308.16 ± 15.16
519.26 ± 10.08
54.83 ± 1.61
11.89 ± 0.53
7
157.21 ± 4.59
301.92 ± 6.09
520.63 ± 5.59
59.28 ± 3.29
12.33 ± 0.49
SCHW
Unrefined
166.29 ± 8.24
517.24 ± 32.42
321.87 ± 11.39
4.56 ± 0.34
2.17 ± 0.11
0
155.85 ± 2.48
301.76 ± 2.14
516.50 ± 9.74
41.80 ± 5.63
15.25 ± 0.76
1
161.30 ± 1.69
305.44 ± 4.70
528.12 ± 2.90
33.13 ± 3.17
15.03 ± 0.83
2
150.86 ± 2.41
269.52 ± 4.43
559.80 ± 8.99
33.41 ± 1.08
11.92 ± 0.43
3
158.55 ± 1.49
275.64 ± 3.43
575.23 ± 3.48
35.41 ± 1.49
12.56 ± 0.22
4
161.37 ± 2.81
268.08 ± 3.67
601.92 ± 2.97
36.63 ± 1.91
13.20 ± 0.17
5
164.42 ± 1.85
261.16 ± 2.92
629.60 ± 5.84
41.53 ± 1.53
15.14 ± 0.32
Wheat Straw Unrefined
160.19 ± 2.87
285.00 ± 7.73
562.28 ± 12.82
33.50 ± 1.79
13.65 ± 0.40
0
164.72 ± 4.12
199.80 ± 8.07
825.00 ± 12.65
55.71 ± 7.14
17.16 ± 3.76
1
162.36 ± 2.35
232.00 ± 16.37
702.40 ± 36.46
43.59 ± 3.10
18.62 ± 1.75
2
163.36 ± 4.87
219.00 ± 3.81
745.60 ± 18.20
45.09 ± 1.96
16.89 ± 2.04
Recycling Yield of the Pulps with Light Refining
It was of interest to understand how the amount of mechani- cal energy input per cycle may impact the results. Addition- ally, it is most probable that WS would not be used in pack- aging at a 100% level but rather in a blend with other fibers. To investigate, the same experimental procedure (Fig. 1) with three pulps, SCHW, WS, a 25% WS and 75% SCHW blend (WS25% + SCHW75%) but with a “light refining” pro- cess was conducted. The refining level was 500 revolutions for cycle 0 (virgin pulp) and 200 revolutions for the follow- ing cycles. This refining level is more suited for hardwood or non-woods and not as suitable for softwoods. The SCHW demonstrated a high yield of approximately 82% for the first cycle zero, and the yields in the subsequent cycles were on average approximately 95% (Fig. 5), slightly higher than the yields for the heavy refining experiments (Fig. 3). It is possible that the majority of the smaller par- ticles were removed during the first cycle, resulting in the yield being higher for subsequent cycles. The number of cycles before complete exhaustion (extrapolated estimate) for the SCHW is 23 for the light refining, much greater than the 16 for the SCHW with heavy refining. It can be con- cluded that the amount of mechanical energy input per cycle
Fig. 5 The Yield (for the individual cycle) and Yield’ (cumulative yield up to that cycle) of multiple recycle loops of SCHW, wheat straw, and WS25% + SCHW75% with a lightly refined condition
is a critical parameter for the yield and extrapolated number of uses results. Wheat straw, on the other hand, produced an average recycle yield of around 89%, consistently 2–7% lower than
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