Did you know that even the best durable label is not fit for purpose unless the adhesive is correctly matched to the surface? This can lead to label failures and potentially wasted samples.
We have produced a series of guides to give you clear information about the laboratory label options that are right for your processes.
Each guide along with our free downloadable Label Specification 'How to' Guide and Checklist will help you understand and work through the different durable labelling options available to you, in order for you to better understand your label requirements.
What affects label adhesive performance?
These 3 factors determine how well your labels adhere to the desired surface:
1. Type of adhesive
The main types of label adhesive are:
- Solvent acrylic based adhesives: used for durable labels. Can be used in harsh processes, lasting 2+ years and often for the life of the product.
- Water based acrylic adhesive: used normally for paper stationary labels and packaging labels such as shampoo and wine bottles, with best performance indoors.
- Rubber based adhesive: used mainly for adhesion to natural products. Poor UV resistance so not suitable for long-term outdoor use.
2. Adhesive thickness
The thickness of the solvent acrylic-based adhesive on a durable label should be matched to the surface material, texture and porosity that you are applying the label to, to achieve the required durability.
For instance, surfaces that are heavily textured require a thicker, softer adhesive to fill in the texture gaps, ensuring that the full surface area of the label adheres to the required surface.
3. Adhesive curing time
Solvent acrylic adhesives are used for durable labels because they cure over time and become more permanent with age.
Adhesive curing is the process of the solvent-based adhesive transforming from a liquid to a solid through a chemical reaction with oxygen.
Once cured, these adhesives achieve a high strength, flexible or rigid bond that resists temperature, humidity, and most chemicals. They get stronger with age.
Water based acrylic and rubber based adhesive don’t have a curing time, they are as strong and as permanent as they will ever be immediately after applying them to a surface and will deteriorate with age.
If you don’t get the right combination of these 3 things; adhesive type, thickness and cure, for your specific labware and process, your labels will fail. More than that, they may initially look like they work but the performance may degrade over time.
Understanding your application surface is critical for good label adhesion
The type of surface the label will be applied to will have a big impact on the adhesive if it is to be permanent for the life of your research or process.
You will need to consider:
- The surface material the label will be applied to
- The texture, shape, flexibility and how porous the surface is
- Surface energy, is it high or low?
- The environment that the surface is exposed to
What challenges does your application surface present?
Different surface characteristics, along with the level of permanency you require for your labels, each present different adhesive challenges.Which categories does your surface fall into?
Smooth flat surfaces – Smooth metals, glass and high surface energy plastics all offer a very good surface for permanent labels to stay put long term, or for the duration needed for removable labels.
Textured and porous surfaces – Textured surfaces reduce the amount of surface area available for the label to stick to. Porous surfaces absorb more of the adhesive. Using a thicker and softer adhesive fills in the gaps, adhering the label to a larger surface area.
Curved or flexible surfaces – Due to the nature of a non-flat surface, using the incorrect adhesive means the label material may naturally want to straighten out and come away before the label has stuck properly. Therefore, an adhesive that grabs and cures quickly is needed to hold the label in place, while it cures.
Low and high energy surfaces – Surface energy refers to how non-stick something is. The lower the surface energy, the more non-stick it will be. Surface energy is an important factor when considering the adhesive bond.
What processes will your label be exposed to?
Think about the condition of the surface and also what the label will be exposed to during use:
Will the labware surface be hot, cold, frozen, or damp?
Will the label come into contact with chemicals, solvents and extreme temperatures during processing?
All of these factors will affect the performance of the adhesive and will therefore need to be considered at the label specification stage.
Other factors to consider if your labels are peeling or falling off
Storage environment – If your labels are not stored as instructed, the adhesive may cure ahead of time or dry out, therefore decreasing or destroying the bond that would have been achieved. To ensure that your labels keep well until they are required, store them at 50% relative humidity, at +/-21ºC in a sealed polythene bag.
Moisture – Moisture and contaminants present on the surface before applying the label affect the adhesive cure, resulting in less adhesion. Applying your label directly to a damp or cold surface can have a significant negative effect on the cure and bond.
Ageing – Non-solvent acrylic label adhesives can dry out with age. Once a solvent acrylic-based adhesive label has been applied, the cure becomes more permanent over time.
Surface material or process change – If the labels are no longer sticking, it could be as a result of a change in the material that the label is applied to or the process that the label has to withstand. You will probably need to re-specify a label to get the correct adhesive for the job.
Contact with adhesive – chalk-coated rubber gloves will render label adhesives useless. Think about how you apply your labels: touching the edge of the adhesive side when positioning your label could be all it takes to make the label lift at the edge.
Correct Pressure – Solvent acrylic adhesives are 'pressure sensitive' which means that they do not stick effectively on contact (contact adhesive), they require pressure to be applied to work efficiently. Labels should be rubbed with your thumb, particularly on the edges and especially on polypropylene tubes to stop the labels from lifting, particularly in freezing conditions.
Use the right adhesive for your process
You should by now have a much clearer understanding of the factors that can affect the adhesion and durability of your labels and how important it is to match your adhesive to your surface and process.
Not sure which adhesive you need? A computer imprintable durable label specialist will have the expertise to be able to recommend the right label for the job, so you can be sure that you will be getting the permanency you need.
Want to find out more?
Read our next guide - Ensuring your labels withstand your processes >
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