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MARINELLI ET AL .
FIGURE 7
Bending test results for UC, PET, and dispersion-coated paperboard: a) bending resistance; b) bending stiffness.
FIGURE 8
Water absorptiveness (Cobb1800 test) results of the
investigated coatings.
FIGURE 9
Moisture permeability (WVTR) results of the
elsewhere 22 . Waterborne dispersions showed barrier properties improvement ranging from 80 – 95%. Still, coat weight should be con- sidered when discussing results, since aqueous dispersions involved in this study led to less than half coat grammage than it was for PET. Both SA-B and experimental coatings achieved performance similar to previous studies with similar dry coat grammage 12,55,59 . Grease barrier resistance, expressed as minutes to spot dyed grease on the uncoated side of the samples, is reported in Table 4. UC samples showed no OGR. The oil penetrates through the material in a couple of seconds after its application on the surface. As a general statement, the different dispersions provided widely variably perfor- mance. Indeed, SA-B, which was the best-performing material for both water absorption and moisture barrier (Figure 8 and Figure 9,
investigated coatings.
respectively) showed the worst resistance, only up to 4 h. On the contrary, both experimental formulations and SA-B + SAP-H configu- ration were able to resist up to 24 h at 60 C. Nonetheless, the best result, that is, similar to PET, was achieved with SAP-H, which was able to resist for more than 24 h. Despite similar results achieved on paper substrates 22,24 , the test- ing conditions involved in this research were harsher because of higher penetration rates caused by higher test temperature (i.e., 60 C instead of 23 C).
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