Online or offline labeling in extrusion blow molding
Labeling behind blow molding machines can result in a bubbled surface of the label, due to bottle shrinkage. There are different techniques to improve / solve these problems.
The material shrinkage is strongly dependent on the materials used (type of plastic, masterbatch, etc …) and the bottle geometry. Reducing the parison increases the shrinkage as well. The bigger the parison, the less the material is stretched when blowing thus reduces the bottle shrinkage. The shrinkage can occur up to 72 hours after blowing the bottle!
The label thickness is important as well, the thicker, the less the label will bend, the lesser is the chance of getting wrinkles on the label surface.
The type of glue used on the label is important as well. There are specific glues, allowing the label still to shift, thus compensating the shrinkage.
The label material has its impact on the shrinkage, different types available, paper, plastic, where this last one has definitively an advantage in recycling as well, as long it is the same material.
Plastic labels tend to have a better ‘shrinkage’ resistance than paper labels.
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