Adhesive Guide Part 1
- Initial Tack: The immediate holding power of the label adhesive on contact with a specific surface. If initial tack is low, it will have low adhesion, allowing the label to be removed cleanly. Adhesives with a low initial tack will build up adhesion over time (i.e. the difference between removable and repositionable). On the flipside, adhesives with high initial tack will have a stronger adhesion and bond to the container much more quickly.
- Ultimate Adhesion: The maximum holding power the label will achieve as the adhesive fully bonds to the surface. How long it takes for an adhesive to gain ultimate adhesion varies and depends on factors like the adhesive’s stiffness, the roughness of the receiving surface and environmental conditions. Depending on those factors, it can take anywhere from 2 – 24 hours for ultimate adhesion to happen.
- Shear Resistance: Simply put, label adhesives with a low shear are soft which allows them to flow into the surface they’re applied. They also have a higher initial tack, but can split apart under stress. A higher shear adhesive is more firm so it doesn’t flow as well into the surface, resulting in a lower initial tack and making it less likely to split apart under stress.
- U.V. Resistance: If your labels will be exposed to ultraviolet (U.V.) light for extended periods, they may be susceptible to color changes or weakened adhesion. Select a U.V. resistant adhesive in cases where your labels will be exposed to U.V. light on your end, or if your labels will be exposed to U.V. light during the printing process (e.g. when a U.V. laminate or coating is applied to your labels) to minimize these effects.
- Solvent Resistance: The adhesive’s capacity to withstand exposure to solvents like water, alcohol, petrochemical solvents, plasticizers, etc. without losing adhesion. The container contents, along with the environment where the product will be used, should be considered.
- Mandrel Hold: How well the label adhesive holds up to a curved or tight radius surface. If an adhesive has a good mandrel hold, it will be harder for the label’s edges to lift up, also known as “flagging.”
- Cold Flow: Temperature is an essential consideration with adhesives. Cold flow refers to the adhesive’s ability to bond (or “flow”) to a container at below normal temperatures. “Cold temperature” and “all temperature” adhesives will work best when the label is applied in cold environments.
- Minimum Application Temperature: When an adhesive isn’t designed for cold temperatures, it will stiffen and lose its adhesive strength as the temperature decreases. Most adhesives have a minimum application temperature of 5-10 °C before they crystallize and become solid. Cold temperature adhesives can work in temperatures as low as -30 °C.
- Service Temperature Range: The temperature range the adhesive can function in after the label has been applied and built up to its ultimate adhesion. Most pressure sensitive adhesives have a range of -54 °C to 93 °C with a paper label stock, or up to 150 °C with a film label stock.
ADHESIVES SUMMARY
- Acrylic – Basic Water-based adhesive for everyday labelling
- Hotmelt – Longer lasting adhesive for harsher labelling
- High-tack – Very strong adhesive for permanent harsh labelling
- Low-tack (Removable) – For adhering labels that needs to be removed again
- Deep Freeze – For low temperature adhesion and labelling for fridge-item labelling
- Ultra Deep Freeze – For labelling of items that will be labelled and stored in freezer rooms