Freezer Labeling Part 2 – How To Choose The Right Freezer Labels

We previously tackled the importance of freezer labels, as well as some of the things that made them special.

Freezer labels allow companies to promote their brands, improve their services and protect their customers and employees. These stickers are indispensable to retail, healthcare, research, and many other industries, so finding the right ones is just as critical as their applications.

A polyester freezer label with acrylic adhesive

 

In this blog, we further discuss the components of freezer labels, the knowledge of which can guide you in choosing the right kinds for your business.

 

What Factors Affect Freezer Label Stability and Readability?

 

In our previous freezer label blog, we explained the processes and conditions that these tags were expected to endure.

Most of them simply undergo repeated freezing-thawing cycles, while the rest are subjected to further stress, e. g. heat, after thawing. With this in mind, it should be easy to understand why these stickers must have unique properties.

The following factors affect freezer label stability and readability:

 

1. Product Shelf-Life

 

Think of the product that’s about to be frozen.

Freezing can extend the shelf-life of unprocessed perishables by a few weeks. Food additives and processing can prolong it by months, whereas vacuuming can stretch palatability for years.

Biological samples can also remain viable for years when vacuumed and frozen. Meanwhile, the stability of chemical reagents depends on a lot of factors, not just their temperature. They include concentration, pH, microbial growth, light reactivity, etc.

Whatever product you have, choose a freezer label that can outlast it. 

 

2. Adhesive Composition

 

Most adhesives exist as mixtures of different molecules. In homogeneous adhesives, molecular proportions and interactions are uniform throughout the mixture. In contrast, they are uneven in heterogeneous mixtures.

Homogeneity is one of the reasons why hot melt adhesives are tough at subzero temperatures. Other molecular characteristics, e. g. elemental backbone, polymer weight, double bonds, polarity, etc. also contribute greatly to low-temperature tackiness.

 

3. Container Surface

 

In the previous blog, we mentioned that molecular movements within the container could weaken adhesive binding during freezing. However, other surface properties can also affect attachment strength.

  • Roughness—rough packaging has more surface area for potential interaction with the adhesive. You can create a very durable freezer label if you apply enough bonding agent to penetrate creases and cushion the facestock’s rear. However, if you have a smooth container, you’ll need a thinner adhesive coat and some pressure to strengthen sticker bonding.
  • Porosity—pores absorb some of the adhesive. As long as these gaps are not very big, freezer labels can stick to porous surfaces well. Sticky tags can bond strongly to non-porous packaging with some pressure.
  • Cleanness—dirt, oil and frost can disrupt the interaction between the container and adhesive, causing premature freezer sticker detachment. Make sure to clean the labeled area first before tagging it.
  • Shape—flat surfaces allow smooth freezer label application, but they also make tags easy to peel. Curved surfaces, like those on vials, disrupt the direction of adhesive pulling forces, making stickers a little harder to remove.

 

4. Facestock Material

 

Paper suffices for a wide range of functions, but it is the weakest of all facestock materials. Plastics are used for creating more durable freezer labels, but not all are safe to use on food packaging. Custom tags can also be made from other materials, although they have limited applications.

 

An ice cream bucket with paper freezer label

 

5. The Freezing Process

 

Contraction and expansion accompanying temperature changes pull the adhesive in different directions, making it prone to breakage. Generally, homogeneous adhesives can endure these changes better than heterogeneous ones. But the differences are not very pronounced unless the freezer labels are subjected to extremely low temperatures.

In retail, temperatures are not much lower than water’s freezing point (32ºF or 0ºC). Colder states are required in healthcare, scientific research and other industries.

 

6. The Thawing Process 

 

Thawing is normally accompanied by water condensation. Moisture can soften the facestock and, depending on the printing technology used, may even smudge it. It can also loosen up a water-based adhesive, like emulsion acrylic. Thawing can weaken freezer labels and make them unreadable unless the right materials are used.

 

7. Printing or Marking Technique Employed

 

You can directly mark or brand your packaging to dispense with labels. You can use ink curing, burning, laser-etching and other techniques for marking the container, depending on its material. The imprints are permanent, but they are also inflexible and expensive to make. 

On the other hand, printable freezer labels allow you to write whatever information you need displayed on your container’s surface. You can also change them whenever you want to, and for whatever reason. They are, however, less durable than direct container markings.

There are four printing technologies used for creating labels on demand, but not all of them are suitable for frozen items.

  • Inkjet—ordinarily, you can print attractive stickers with your good old inkjet printer. However, inks have water-soluble dyes that may smudge during thawing. Therefore, this technique is not ideal for creating freezer labels.
  • Laser—laser printers, which rely on molten, charged plastic powder for printing, can create smudge-proof, fade-resistant freezer labels. However, they can only be used on paper facestock.
  • Direct thermal—this technology lets you create crisp, smudge-proof freezer labels, although they are expected to fade after 6-12 months. You can use a 203-dpi gadget for barcoding big packages that you expect to sell within a short time. For smaller containers, e. g. lab micro-vials, a resolution of 600 dpi is required. Direct thermal printing is not often used for branding because colors are limited to black and red.
  • Thermal transfer—this is the most widely used technology for printing freezer labels. Thermal transfer printers let you make smudge-proof, fade-resistant and professional-looking labels. They use various colors and facestock materials. Thermal transfer is the most expensive of the four technologies, but it is also the most versatile and useful for branding. It can be an excellent investment if you expect to make freezer labels for a long time.

Alternatively, you can handwrite your freezer labels or have them custom-made. Of course, handwriting retail tags is prone to errors and makes them look unprofessional. Meanwhile, custom-printed stickers are more expensive, and they cannot be used for labeling point-of-care and research specimens.

 

8. Chemical and Physical Exposures

 

Chemical spills can weaken paper, while plastics are generally more durable. Polyvinyl chloride (PVC), a plastic material, is UV-resistant. Thermal transfer prints can endure acid, alkali and organic solvent exposures, unlike the others.

Organic solvents like DMSO, acetone, ether, etc. can dissolve some adhesives, particularly organic solvent-based types. Water-based and hot melt adhesives are more stable to these compounds at lower temperatures.

Heat exposure, as in autoclaving, can reduce the tackiness of some adhesives. When you need to heat a freezer label along with its container, it’s best to check the adhesive’s service temperature range, or the temperatures wherein it can remain useful.

Chemical spills are not much of a concern when dealing with most frozen retail products. However, they do matter more in research, healthcare and chemical manufacturing.

 

A researcher mixing chemicals in the lab

 

9. Label Size and Shape

 

Smaller freezer labels are generally easier to displace than big ones. This is due to the small facestock-adhesive contact surface area. However, wrapping them around curves can make them harder to remove.

As we’ve mentioned earlier, surface curves, like those in rounded bottles and vials, serve as a barrier to adhesive pulling forces. However, make sure to maintain barcode readability if you need to wrap freezer labels around curves.

 

10. Convenience of Application

 

You can create freezer labels by applying the adhesive and facestock separately on the packaging. This can make very tacky tags and help you save costs. However, without automated machines, the process is time-consuming, prone to errors and may cause ergonomic injuries among your staff.

On the other hand, you can just buy printable self-attaching freezer labels. They have pressure-sensitive adhesives, and you can apply them easily with or without the aid of robots. These special stickers, however, are pricier than ordinary ones.

Choose the application technique that best suits your needs and budget.

 

11. The Adhesive’s Application and Service Temperatures

 

These metrics are good indicators of an adhesive’s usefulness in different environments.

The application temperature is the temperature at which an adhesive is applied. A minimum application temperature close to water’s freezing point indicates that the bonding agent can remain tacky at subzero states.

Meanwhile, the service temperature range indicates the bounds within which the adhesive can remain sticky. Adhesives with very low minimum service temperatures are good for cryogenic labels. Those with high maximum service temperatures are useful for oven-drying and similar purposes.

Ask your trusted supplier about these parameters to make sure that your freezer labels are appropriate for their intended use.

 

12. The Need for Food-Grade Materials

 

Not all freezer label materials are universally approved for packaging food. For example, PVC is included in California’s Proposition 65. It requires companies to caution customers about potential toxic exposures when using their products.

PVC and the ingredients for its production can cause cancer. Keep this in mind if you’re thinking of using it for a consumable item. 

 

A labeled pack of frozen beef

 

We cannot emphasize enough the importance of freezer labels. They are costlier than other kinds of stickers, but their properties make them useful for vital jobs. Choosing the right materials can help you avoid unnecessary costs, delays and customer dissatisfaction.

 

What Facestock Materials Are Used in Freezer Labels?

 

Paper and plastic are the most commonly used freezer label facestock materials, but others have also been employed. Remember that the substance you choose must be compatible with the printing or marking technology you use.

 

Paper

 

Paper is the cheapest, most available facestock material. It is the easiest to design, and it goes with any kind of printer, container and adhesive. Using the right technology, paper freezer labels can become fade-resistant. They can tolerate a broad temperature range, and they are FDA-approved for food and cosmetic packaging. They are also environment-friendly.

Paper’s main drawback is its relative weakness to moisture, chemical exposures and mechanical forces. It has many applications, but consider plastic and other durable materials for more demanding tasks. 

 

Blood bags usually have paper freezer labels

 

Plastic 

 

Plastic freezer labels are quite pricey, but they get a wider array of jobs done because of their durability. They are easy to design just like paper, but can only be made by handwriting, direct marking and thermal transfer technology.

Compatible adhesive types include hot melt and organic-solvent based polymers. Aqueous bonding agents do not go well with plastic facestock, especially if used in extremely cold environments.

Plastic freezer labels are fade-resistant and highly stable to moisture, chemical exposures and most mechanical forces. Unlike paper, however, they can melt at very high temperatures. Certain plastic substances, like PVC, are UV-resistant.

Plastics are formulated for different purposes. For making freezer labels, the most commonly used ones are polyester, polypropylene, polyethylene and PVC. These substances can be softened or stiffened, depending on the manner of film collection and plasticizer content.

Plastic is compatible with any container material. However, health and environmental considerations must be factored in when using plastic freezer labels.

 

A roll of polypropylene freezer labels

 

Miscellaneous

 

Metal, fabric, ceramic, glass, etc. are rarely used for making freezer labels. However, special types can be produced if necessary. And, except for fabric, they will need special marking processes. The metals normally used are stainless steel, copper and aluminum.

Of these materials, fabric is the cheapest and easiest to design. It can be changed on demand and goes well with any adhesive and packaging type. Fabrics are safe to use on food containers. Thermal transfer technology will suffice for fabric freezer labels. Fabric can tolerate a broad temperature scale, but it is relatively weak to freezing-thawing cycles and chemical spills.

Metal, ceramic and glass are less commonly used, as they are expensive and less available. They require special marking technologies, so they cannot be adjusted easily when needed. They are very sturdy and can withstand extreme temperatures, although a strong impact can break glass and ceramic. These tags are usually found in laboratory, transportation, and space applications, but you can make your packaging stand out with these unusual freezer label facestock types.

All of these materials are recyclable and FDA-approved for packaging.

 

 

Paper and plastic suit most products and are very convenient to use, so they are the first choice for making freezer labels. However, you don’t have to limit your options. With a little creativity, you can address your branding needs even with a small budget.

 

What Adhesives Are Used in Freezer Labels?

 

A broad variety of bonding agents have been used on freezer labels. They are classified in many ways, but industries commonly divide them according to the following characteristics:

 

Chemical Composition

 

There is a myriad of polymers that go into adhesives. But not everyone can bind different objects well while frozen. In freezer labels, the following substances can be found:

  • Pure hydrocarbon polymers

These polymers strictly contain carbon and hydrogen in their chains. They are best applied with organic solvents, as they do not mix with water. They can also be incorporated in hot melt adhesives in different proportions.

Polyolefins are petroleum-derived substances that have compact repeating units. They include polyethylene, polypropylene and polybutene.

Isoprenoids, obtained from natural or synthetic rubber, have repeating units that are somewhat longer. They include styrene derivatives, which are common ingredients of hot melt adhesives.

Both groups can be formulated to remain tacky (viscoelastic) at very low temperatures. For example, the addition of double bonds at certain molecular sites can lower the freezing temperature. This prevents the polymer from stiffening right away when cooled.

  • Other carbon-based polymers

These polymers have long carbon chains, but they also have oxygen, nitrogen, phosphorus and other non-carbon, non-hydrogen elements. These additional elements impart properties that make adhesives stronger. Included in this broad class of compounds are the following:

    • Acrylates
    • Ethylene-vinyl acetate (EVA)
    • Polyamides
    • Polyesters
    • Polyurethanes
    • Epoxides
    • Polycarbonates
    • Fluoropolymers
    • Polypyrroles
    • Lactones

The extra elements can enhance other characteristics like color and water solubility, as well as resistance to UV, burning, oxidation, etc.

  • Silicone adhesives

Silicone adhesives have a predominance of silicon, rather than carbon, in their molecular chains. They may contain some carbon, as well as hydrogen and oxygen. Pure silicones are very expensive but can withstand wider temperature ranges than carbon polymers.

Aside from the cost, silicones’ main drawbacks are their potential health and environmental tolls. Silica, their main ingredient, can cause lung problems and cancer. Silicon polymers are non-biodegradable. They can accumulate in the ecosystem if they’re not recycled. Note that silicon recycling plants are rare. 

The adhesive’s chemical makeup dictates most of its properties, but it is not the only one determining its suitability for freezer labels. You don’t need to fully grasp the chemistry of adhesives, although the minimum application temperature and service temperature range largely depend on it. However, keep in mind that these are parameters that you can simply ask your supplier to provide.

 

Mode of Application

 

The discussion here applies only to paper and plastic freezer labels. These stickers can be applied in two ways.

  • The adhesive and facestock are applied separately

In this mode, we’re talking about applying the bonding agent, placing the facestock on top and letting the adhesive set. Therefore, the freezer label is not self-attaching.

The bonding agent is a “structural adhesive.” It sets by solvent drying, UV curing, cooling, or chemical change, depending on its composition.

Manual and mechanical modes of application are acceptable. Manual application requires low overhead costs, but it is inconvenient, time-consuming and waste-prone. 

  • The adhesive and facestock are applied together

In this mode, the freezer label is self-attaching and depends on pressure-sensitive adhesives. Such bonding agents are chemically similar to structural adhesives, but they are designed to have long open times (the time it takes an adhesive to set or harden). Manual or mechanical pressure promotes setting in the bonding agent.

Self-attaching freezer labels are more convenient to use, but they require high overhead costs. Still, they are indispensable to many small businesses, medical facilities and research labs.

Convenience and efficiency are huge factors in choosing one mode over the other. Choose the method that is affordable and appropriate for your needs.

 

 

Presence of Solvent in the Adhesive

 

The solvent allows you to apply the adhesive evenly on the surface. However, its presence also means that the bonding agent is heterogeneous. Solvents can dry up, but a little amount remains to keep the adhesive tacky. Freezer label adhesives can be classified based on this.

  • No solvent

Hot melt adhesives are the best examples of solvent-less bonding agents. They are heated and melted before application, and cooling causes them to set. They can bond with any surface, and their homogeneity makes them less vulnerable to fracturing in subzero temperatures. However, unless they’re made of silicone, their heat sensitivity makes them less useful for heat-requiring applications, such as autoclaving.

Pressure-sensitive hot melt adhesives are specially formulated to have long open times. Freezer labels using such bonding agents can endure very low temperatures for long periods. However, they are some of the most expensive stickers, so they are reserved for special purposes, like lab and medical cryotagging.

  • Dissolved in an organic solvent

Organic solvents include toluene (rugby’s solvent), ethyl acetate, dimethylformamide, methyl ethyl ketone, etc. Organic solvent-based adhesives set as they dry, but they make very tacky and durable freezer labels. Organic solvents are flammable and can irritate the breathing passageways, so extreme care must be taken when they’re applied or stored.

Alternatively, you can use pressure-sensitive freezer labels with organic solvent-based adhesives. Aside from having good cold tolerance and wide surface compatibility, they can remain tacky at temperatures higher than their hot melt counterparts can endure.

  • Suspended in water

Aqueous or water-based adhesives are heterogeneous polymer suspensions. They also set as they dry, and their service temperature ranges depend on their polymer backbones.

When used in freezer labels, aqueous carbon adhesives can only endure temperatures close to water’s freezing point. In contrast, silicone agents have better cold and heat tolerance. Aqueous carbon adhesives are safe and eco-friendly, while water-based silicones can be harmful to health and the environment, as we mentioned earlier.

Emulsion acrylic is an example of a water-based carbon adhesive. It is commonly used in self-attaching retail freezer labels, e. g. frozen food labels. Some acrylics can withstand autoclaving temperatures, so they can be used in healthcare as well.

To know what kind of adhesive to apply on your freezer label, consider its purpose and the temperature range wherein you expect it to remain functional.

 

Permanency

 

Lastly, freezer labels can be permanent or removable. The difference between them is the time that it takes for the adhesive to set. Removable labels can be peeled cleanly when they’re freshly applied, but they can harden and become difficult to detach with time. When choosing between these two, you must figure out early how you will use your freezer labels.

 

A thawing microvial with a tiny barcode label

 

This information on freezer labels may be a handful. But like we keep saying, these special tags serve a unique purpose, and finding the most suitable ones is crucial. It’s one of those aspects of business where you can say, “Knowledge is power,” and that’s exactly what we hope to have given you. 

 

Conclusion

 

We just presented a comprehensive guide for choosing freezer labels. In finding the right stickers, you need to think about the properties of the frozen item, packaging, adhesive, and facestock, as well as the costs and working temperatures. This task is very important as it can impact product presentation in retail and service delivery in other industries. We hope that this guide helps you find the right freezer labels for your business.

 

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