Choosing your labels will inevitably involve choosing the right adhesive, which can be difficult if you aren’t aware of your options. This article will serve to inform you about the most common adhesives used on self-adhesive labels, most of which are based on rubber or synthetic resins.
Rubber Means Synthetic
Although it’s true that pure rubber was traditionally used to make rubber adhesives, almost all adhesives referred to as rubber-based are now made of synthetic materials. Regardless, rubber adhesives offer a higher degree of adhesion than do their acrylic counterparts. They also adhere to surfaces more quickly. Rubber adhesives bond particularly well to plastics, but are not as resistant to UV rays and ageing as acrylic-based adhesives.
Acrylic adhesives are actually constructed of synthetic polymer. Although they don’t attach as quickly to surfaces as rubber adhesives do, a label with an acrylic adhesive will be stronger and more durable. As well, acrylic adhesives become longer-lasting over time. They can endure temperature extremes and when exposed to chemicals can outperform rubber adhesives. Acrylics age well and offer high UV resistance. They can also be easily modified for any application.
Adhesive Formulation: Carriers
Several types of adhesives include something called a carrier in their formulation, which is what the adhesives active components are dispersed or dissolved in. Without a carrier, an adhesive would be completely solid.
Application-Specific Label Adhesives
Demanding applications will usually warrant the use of labels with solvent-based adhesives. This kind of system contains a solvent that evaporates during drying. The solvent is then able to be reused, which is feasible considering that these adhesives are higher in cost. Solvent-based adhesives can be used on a wide variety of substrates and offer some tolerance for humidity and low temperatures.
Water-based adhesives are enjoying increased popularity due to their environmentally-friendly and non-chemical base. These adhesives are not flammable and can resist high temperatures very well. They are also ideal for a wide range of applications because they offer strong adhesion.
Curable adhesives are relatively new, being composed of UV cross-linkable acrylics. This completely solid adhesive is melted before being pumped to the coating station. There, the adhesive is cross-linked with UV radiation, which gives it light and water resistance, as well as increased resistance to heat and chemicals.
Similarly, hot-melt adhesives are also completely solid. This type of adhesive is heated to above-melting point and then applied to the substrate. Hot-melt adhesives are ideal where labels must be adhered to moist substrates. They offer an incredibly strong and fast adhesion to difficult surfaces, and are often used in low-temperature applications.
Factors Relating to Suitable Adhesives
When trying to choose the right adhesive, several factors should be considered. For example, all adhesives will age over time, as well as be affected by temperature and conditions on the substrate or around the site of adhesion.
Yellowing, loosening and hardening are all possibilities with any adhesive over time, making it important to consider the shelf-life of each. Age resistance is a feature of acrylic adhesives, as is resistance to UV light.
An adhesive’s properties will be affected by temperature, increasing in hardness and decreasing in stickiness as temperatures drop. High temperatures can cause adhesives to soften and possibly weaken at label edges. The temperature when labelling takes place, as well as the temperature of the environment when the label is in service are both critical to its level of effectiveness.
The substrate also affects label properties. Rough surfaces may not allow for complete adhesion. Water-based adhesives will be more tolerant of water, but in cases where moisture and humidity will be extreme, solvent-based and hot-melt adhesives will offer better performance.
Whether you require your labels to have a temporary bond, last for years or need them to be able to be frequently repositioned, knowing the properties of commercially-available labels and their adhesives will help you to make the best choice for your application.