Fractal Fract. 2025 , 9 , 123
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3.2. Surface Friction of Printing Paper Table 3 presents the surface friction parameters, including the COV in percentage, of the printing paper samples based on 10 measurements for each sample. As shown in Table 3, the surface friction parameters exhibit similar trends to surface roughness parameters. The COV values of FMAD are less than the MIU values. This implies that the MIU parameters also vary, depending on the measurement conditions for calculating the friction profile parameters [17,23]. Thus, similar to surface roughness parameters, the independence of FMAD on measurement conditions is obvious.
Table3. Surface friction of printing paper samples.
MIU
FMAD
Sample
Mean 0.187 0.230 0.249 0.162 0.179 0.119 0.279 0.272 0.218 0.144 0.203 0.250
COV 21.9% 21.4% 25.2% 18.8% 21.4% 15.8% 20.4% 16.0% 21.9%
Mean 0.029 0.039 0.036 0.027 0.038 0.025 0.043 0.037 0.036 0.034 0.037 0.031
COV 9.9% 17.0%
P&W1 P&W2 P&W3 P&W4 P&W5 P&W6 P&W7 P&W8 P&W9 P&W10 P&W11 P&W12
9.7%
13.9% 11.6% 12.4% 16.1% 13.5% 10.5%
9.0%
8.2% 9.2%
19.3% 17.3%
15.1%
In addition, a comparison between P&W11 (uncoated) and P&W12 (coated) revealed thatwhile MIU increased, FMAD decreased. This result demonstrates that coating signif- icantly reduces the fluctuations in the friction profile, which cannot be captured by the conventional friction parameter MIU [23]. These findings strongly support the argument that FMAD is a more informative parameter for characterizing surface friction than MIU . Figure 8 compares FMAD and MIU , revealing a weak correlation between the two parameters (R 2 = 0.463). This weak correlation highlights the independence of these parameters. FMAD is calculated by subtracting the MIU value at each data acquisition point, thereby allowing FMAD to represent the variation in surface friction profiles rather than the COF. Thus, FMAD is independent of COF and can provide a distinct measure of surface friction variability [17,22,23].
Figure8. Comparison of FMAD and MIU .
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