A label adhesive may perform well at room temperature but develop edge lifting or label detachment in cold storage. Another adhesive may provide strong initial tack yet begin to ooze from the label edges after high-temperature transportation or summer storage. When these problems occur, it is not enough to ask whether the adhesive is simply “sticky enough.” Its glass transition temperature (Tg) must also match the actual application and service conditions.

A lower Tg allows the adhesive layer to remain soft at low temperatures and wet the application surface more quickly. This makes it suitable for cold-chain labels, freezer labels and certain low-surface-energy substrates. However, if the adhesive becomes too soft at elevated temperatures, it may creep. A high coating weight can further increase the risk of adhesive ooze and reduced holding power.

An adhesive with a higher Tg generally provides better cohesive strength, helping to control high-temperature creep and reduce adhesive residue after removal. However, as the service temperature approaches the Tg, the adhesive layer becomes stiffer and loses some of its ability to wet the surface during label application. Under cold conditions, this can result in poor initial bonding, false adhesion and edge lifting.

Within the existing water-based acrylic label adhesive systems developed by Anhui Sinograce Chemical, the theoretical Tg of general-purpose permanent grades is typically designed between −45°C and −30°C. Cold-chain and freezer-label adhesives require a lower Tg, while removable and low-ooze grades generally use a moderately higher Tg together with controlled crosslinking to maintain cohesive strength.

When selecting a label adhesive, both the labeling temperature and the subsequent service and storage temperatures must be considered. The facestock—whether paper, PET, PP or PE—the application surface, such as glass, cartons, PET bottles or HDPE containers, the adhesive coating weight, and whether the label is permanent or removable will all affect the final performance.

The aim of Tg design is not simply to make the adhesive softer or harder. It is to achieve the right balance between initial tack, peel adhesion, holding power and resistance to adhesive ooze for the intended application.