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MARINELLI ET AL .
FIGURE 2
Tray blank after creasing.
TABLE 2
Tray forming parameters.
Parameter
Units
Min
Max
Blank moisture content
[%]
4.0
5.6
Blank holding force
[kN]
0.546
1.014
Temperature
[ C]
100
120
Pressing speed
[mm/s]
45
90
Subsequently, coat defects due to press-formation were qualitatively evaluated using E131-dyed water and ethanol.
die-cut with the longer side aligned to the Machine Direction (MD) to provide higher tray stiffness (Figure 2). Berry trays (142 mm 94mm 50 mm) were press-formed from conditioned tray blanks, with main dimensions of 211.3 mm 167.3 mm, varying blank moisture content (MC), blank holding force (BHF), temperature, and pressing speed — dwell time was constant to 0.6 s. PET blanks were formed maintaining the MC within the 8 – 9% range. The moisture content was assessed by testing 5 g of material with an Adam Equipment (Milton Keynes, UK) PMB 53 Moisture Analyzer. Parameters ranged as reported in Table 2 and their effect was assessed following the previously mentioned sequence. Such specific order was because of preliminary tests, which showed a sticking behaviour of both H39K 80 and H39K 60. Dynamic friction tests at different MC (i.e., 2.4%, 7.4% and 11.0%, due to dif- ferent conditioning environments) were performed on three samples for each coating, to be tested along MD. Dynamic friction equipment consisted of a 0.2 kg sled stuck to a sample-coated side facing a smooth stainless steel sliding plane.
FIGURE 3
Average dry coat grammage for each coating
investigated in this work.
2.2.7 | Statistical analysis
Graph representation was performed with MS Excel (all error bars represent standard deviation), whereas statistical analysis of the heat sealing experiments (see Section 2.2.5) was carried out using Minitab 21.3.1. Linear Pareto charts were produced to evaluate the relevance
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