Pressure-sensitive adhesives are far from one-size-fits-all. Some adhesives are engineered to have good holding power at arctic temperatures. Some stick permanently, and some can be removed easily by the customer. Yet others are designed to help labels stay snug around tight-radius containers.
It therefore stands to reason that selecting an adhesive is complicated. Your label supplier will guide you through the process, helping you choose the adhesive best suited to your product, its container and its end-use environment.
Here, we’ve outlined the universal attributes of adhesives to help you understand what goes into choosing the “right” adhesive for your product label before reaching out to a label supplier.
Minimum application temperature
This is the lowest temperature at which your label can be successfully applied to the container. Most adhesives have minimum application temperatures between 40 to 50° Fahrenheit (4.4 to 10° Celsius).
Applying these types of labels at temperatures below that range will lose its pliability, become stiff and weak (called crystallization). If you need to apply your labels at lower temperatures — such as in a cold warehouse — then it’d be wise to choose a cold-temp adhesive, which will maintain its integrity even when applied at temperatures as low as -20° F (-28.9° C).
This describes the temperature your labels can withstand after being applied and the adhesive has completely set (see “ultimate adhesion”).
Let’s say you apply a typical pressure-sensitive label in the recommended application temp range of 40 to 50° F and let it set for 24 hours. Most adhesives will maintain optimal adhesion in service temperatures from -65 to 200° F (-54 to 93° C) with a paper facestock and as high as 300° F (148.9° C) with a film facestock.
Cold flow is an indication of how well an adhesive will adhere or bond to your containers when exposed to colder temperatures. Many adhesives, when exposed to lower temperatures, can become more viscous or thick — which can cause adhesives to collect in label applicators or can even cause failure of the adhesive. If you plan to apply your labels at lower temperatures, and your containers are going to be cold during label application, you will likely need a cold-temp or all-temp label adhesive.
This is the holding power of the adhesive immediately upon application. Adhesives with a high initial tack bond almost instantly with the container, while adhesives with low initial tack have a weak bond at first and don’t reach ultimate adhesion for 24 to 48 hours.
Some label adhesives with low initial tack allow you to remove and reposition the label immediately after application, because the adhesive is designed to get stronger over time. Other label adhesives are designed to be removable throughout the product lifecycle, as with coupon labels.
Ultimate adhesion refers to the maximum holding power of the label adhesive after it fully bonds with the surface of the container. Pressure-sensitive labels will only achieve ultimate adhesion if they are applied in the appropriate temperature range and left undisturbed for the appropriate dwell time.
The time an adhesive takes to achieve ultimate adhesion depends on three main factors: The texture of the container, the temperature and the shear (or stiffness) of the adhesive. Generally adhesives take 24 to 48 hours to reach ultimate adhesion, although there are some designed for dwell times as short as two hours.
Mandrel hold refers to how well your adhesive sticks to curved containers. Adhesives with good mandrel hold will stick to tight-radius containers without “flagging,” or developing bubbles or lifting along the edges of the container. The exception is when your label is too large for the bottle or container at the point of a curve or taper. No degree of mandrel hold will prevent flagging if your labels were not properly engineered for curves or tapers.
Shear resistance refers to the strength of a label adhesive. Low-shear adhesives are “softer” and will flow more easily across the surface of the container. Generally low-shear labels have higher initial tack, but are vulnerable to strain, and can break apart during product use. Adhesives with high shear are stiff and viscous, and have lower initial tack. But they’re less susceptible to cracking and tearing under stress.
Solvent resistance refers to how well the adhesive resists solvents like alcohol, plasticizers, petrochemicals and the universal solvent — water. If your product can spill out and come into contact with your labels, or solvents are likely to be around your product while in use, you may need a solvent-resistant adhesive. While a top coating like varnish and laminate can protect the facestock, adhesive will still be vulnerable at the labels edge.
There’s a lot to think about when choosing an adhesive — and that’s just one more reason we encourage careful planning with your printer. Providing them with as much information as possible about your products, containers and the environmental conditions your labels need to withstand will help them guide you toward the best facestock and adhesive for your application.
To take the guesswork out of designing your label, we can provide you with blank label stock that you can test on your product container. If you send us your container, tell us about the environment your product will be used in and describe the desired look of your product label, we’ll send you samples to test on your products before you buy. Order your free samples today.