Weber Etiketten: Low temperatures alter the behavior of the adhesive and this must be taken into account

Did you know that every glue has a “freezing point”, known as the glass transition temperature? Outside of this temperature range the glue serves as a bonding agent – its molecules “lock” and it loses its ability to affect the pores of the package. This is one of the most common causes for labels to peel off regarding the food industry, especially during the production of frozen foods. How do we know if the chosen labels are suitable for sudden freeze? Why is “the stronger” glue not a solution, when we’re talking about low temperatures and if it is possible to remove this obstacle via engineering methods? For a professional opinion regarding these technical challenges we contacted Weber Etiketten Bulgaria, whose expertise in self-adhesive and cardboard labels provides answers to the most difficult questions in the sector.

For industrial conditions, the most used materials are acrylic adhesives, which are good for room temperature but have one major weakness – the molecular structure is meant to move only in a tight temperature range. Once the temperature goes below the glass transition range, there’s a change in phase, which alters the very nature of the substance. The glue stops acting as a fluid and becomes a hardened body. In this condition, it can no longer “contain” the surface or enter the microscopic pores of the package. The real problem, however, comes from the movement of the materials, as cold shrinks the cardboard or foil, while the hardened glue doesn’t move. Under these conditions, the "glassed" bond has become completely inelastic and cannot compensate for this movement, causing the adhesive to mechanically crack and peel off.

"To avoid such a scenario, it is important that the adhesive has a low modulus of elasticity at sub-zero temperatures. Otherwise, the label behaves like a piece of ice on a flexible surface - at the slightest tension, the bond simply breaks," Weber Etiketten Bulgaria commented.

Photo source: Weber Etiketten Bulgaria, Weber Marking Systems