Oxygen barrier properties of Thermoformed trays manufactured with Different Drawing methods and Drawing Depths

Summary

A comparison was made of oxygen barrier properties and wall thickness distribution of different thermoformed trays. The thermoformed trays were manufactured with three drawing depths and two different thermoforming methods; with and without plug-assist. Four different polymer combinations were evaluated. The oxygen transmission rate (OTR) [cm(3)/(package/day)] was measured at three conditions (23degreesC/50% relative humidity (RH) with 0% RH inside, 6degreesC/80% RH with 0% RH inside, and 6degreesC/80% RH with 100% RH inside. Wall thickness was measured at five different positions in the trays. In general, temperature had more influence on the oxygen transmission rate (OTR) than the humidity. The OTR in the packages increased with increasing drawing depth, but the increase was not linear. Other effects besides thinning, such as orientation, may have influenced the OTR, since the relationship between OTR, given as cm(3)/(m(2)/day), and the drawing depth was not linear. Plug-assisted thermoforming only had an effect on the OTR in trays with 70 mm drawing depth made of 600 mum thick laminate of PP/PE, which was probably due to exceeding the maximum drawing depth of this material. There was no correlation between the OTR value in the packages and the wall thickness in either of the positions, but a quite high correlation between the drawing depth and the relative wall thickness in all measured positions was observed. Copyright (C) 2004 John Wiley Sons, Ltd.