The PS trials showed the results that can be obtained at commercial converters at large scale processes. The end articles might be trays, yogurt cups or ice cream containers. The PS trials were taken as a bench mark for the PLA trials following. The dissolved gas in the polystyrene polymer melt let the MFR increase from 3,9 to 4,5, so only a slight change that has no significant influence on the process stability. The density reduction down to 0,67 g/ccm shows the typical -40% that are possible in a mono layer sheet. For mechanical reasons a useful weight reduction of 20% is used by industrial converters. The foam structure of the PS is very fine as shown in picture 5a).
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