Longer shelf-life is something that has long been in demand for every company in the converting industry. Today when purchasing a material it comes with a recommendation that it is processed within 3 to 6 months, causing additional expenses due to the logistic demands for internal handling; something that does not bring any value, but if it is not done correctly it will result in huge amounts of material having to be scrapped.
The preferred method to prepare freshly extruded plastic film for later converting processes is Corona treatment and it has been since Vetaphone’s founder Verner Eisby, invented the technology in 1951. However, regardless of how high a material factor [W·min/m²] has been applied to the material upon extrusion, it always decays over time. Depending on a number of factors like material type and the additives within, the decay can be measured from within minutes, to weeks or months.
Today the industry standard seems to be that on the bottom of the material data sheet there is a small note saying “must be used within 3 or 6 months from delivery” which is the only indication of the shelf-life you can expect. However nothing is mentioned regarding ageing, which makes it difficult to set the exact material factor needed on the Corona system. This leads to the Corona often just being set to maximum, regardless of the material being processed which results in an unnecessary use of power.
The new EASI-Plasma Grafting Technology solves the ageing problem, as materials can be treated to high and lasting dyne levels guaranteed for 12, 18 or 24 months. This is not to be confused with a recommendation remark, it is an actual guarantee that the dyne level will not decay within the guaranteed period.
The graph shows ageing on BOPP. The same material has been treated with Corona and 2 different types of the EASI-Plasma Grafting Technology. The Corona treated material quickly decays to its “native” value of 32 dyn/cm, whereas Standard Grafting decays at a similar speed to 46 dyn/cm and then stays there whereas the Advanced Grafting shows no decay for 18 months and counting.