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MARINELLI ET AL .
FIGURE 6
Tensile test results for both UC, PET, and dispersion-coated paperboard: a) tensile strength; b) strain at break; c) average maximum
force; d) tensile energy absorption.
No significant difference could be observed in the investigated parameters because of different DC because of either close average value or standard deviation – as it is for bending stiffness (Figure 7.b). Such results are coherent with previous findings 53,54 . The rationale is in the low dry coat grammage compared with the substrate one, with the former accounting for less than 5% of the total grammage. The previous statement might be supported by the results for PET-coated substrate, generally showing better mechanical performance to both MD and CD. Indeed, the PET grammage fraction is slightly more than 10% of the total grammage.
even SAP-H, a commercial heat-sealable grade, showed a water absorption that was 50% lower compared with H39K 80. On the other hand, SA-B achieved similar results compared with PET-coated paperboard, as well as SA-B + SAP-H coating configuration. Coherently to previous studies 22,55 – 57 , the presence of kaolin in the formulation proved to be of low benefit for improved water bar- rier properties because of its hydrophilic nature 58 . In particular, higher kaolin content generally led to increased water absorption. However, in terms of magnitude, such results differ from previous results 22,24 with the same coatings but different substrate, especially for experi- mental coatings, where higher dry coat grammage led to even worse relative performance. WVTR (Figure 9), once again, showed how SA-B provided perfor- mances similar to PET (both less than 20 g/(m 2 day), whereas experi- mental formulations achieved results around 40 g/(m 2 day), with H39K 60 showing slightly lower WVTR, similarly to what described
3.3
Barrier properties
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Cobb1800 test results are reported in Figure 8. Experimental formula- tion provided minimal barrier compared with other coatings. Indeed,
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