Blister Packaging, Part 2
By Tom Weber
July 15, 2020
In the May/June issue of BoxScore, we took a look at blister packaging—mainly descriptions of the types and what it’s best used for. In this edition, we’ll dive deeper into the world of blister packaging, particularly the stocks, coatings, supply chain, recyclability, and performance. First up, it’s all about starting with the right materials and understanding the considerations that must be made before sourcing.
Factors in Sourcing Blister Card Raw Materials
Blister cards are an integral part of blister packaging. The material from which they are formed and the materials with which they are coated impact everything from security and printability to how well the package seals and how economical it is to produce. So it’s vital to ensure that the blister card material you choose is the optimum match for your functional requirements.
- In general, there are four main factors to consider:
- What should the blister card stock itself be made of?
- What coatings will the blister card require?
- How does the blister card stock fit into the supply chain?
- What testing procedures are needed to ensure the highest quality and performance?
Of What Should the Blister Card Stock Be Made?
Blister card stock, or substrate, is available in a variety of options that can be tailored to the goals of the packaging and the requirements of the manufacturer.
Standard display packages can be made with any grade of paperboard. All blister card stock is made from clay-coated paper, which has a smooth clay coating applied over a rough paper base. Standard clay-coated paper is a basic platform that can fulfill most blister card stock needs at the most economical cost. The two primary types of blister card stock are:
- Standard clay-coated paperboard: It is often referred to as CRB or CCN and is basically recycled paperboard that has been clay-coated. Though this type is the most economical, it has limitations. It does not have the fiber strength, stiffness, or consistency of virgin paper due to its varied recycled materials content from day to day, and even with the clay coating, the printed finish may be of a lower grade due to the surface inconsistencies.
- Solid bleached sulfate (SBS):
What Coatings Will the Blister Card Require?
Selecting the type of blister card stock is only the first step in designing the optimum blister package for your product. The function of the card is ultimately determined and enhanced by the types of coatings that will be applied to it, and many coatings are highly specialized. The coating and the card must be considered as an integrated unit, so it’s important to consider the specific characteristics the packaging must meet:
- Adhesion requirements. Does the coating need to adhere to itself (in a fold-over card), to a different type of card stock (a card-to-card application), or does it need to heat-seal directly to thermoformed plastic film?
- Heat seal or cold seal? Coatings that can be heat-sealed offer excellent reliability and durability. When heat sealing is appropriate, it’s important to get a few pieces of additional information. What temperature is needed to achieve a good seal? Typical temperatures range from 190 to 210 degrees Fahrenheit. Also, what is the heating element dwell time? It typically ranges from two to five seconds. Cold sealing (or pressure-sensitive sealing) enables the card stock to be joined using only pressure and no heat. Cold sealing is harder to use in high-speed packaging operations and is much better suited for small runs.
- Resistance to tearing. Does the blister pack require an additional film lamination to add tear resistance? And if so, how much tear resistance is required? Permanent adhesives are used to laminate films; the advantage of this is that they create a structure that prevents tearing and product tampering. Higher tear resistance can add significantly to the cost of the final unit, and it typically is employed only for high-value retail-display products.
- Ease of opening. How easily should the package be opened? Should it be easy to open, or does it need to be robust in order to add extra security?
What Other Participants in the Supply Chain Need to Be Consulted?
Applying blister card coatings is a highly specialized process—so specialized, in fact, that coating providers often focus solely on the exacting standards that govern the creation, chemical engineering, and application of the card-coating process. That means the card stock is often the result of a supply chain that includes the paper mill, the coating company, and the commercial printer that creates the card for actual insertion by the product packager. Therefore, there are additional important issues to address:
- The coating company must consult with the supplier of the raw paperboard. We’ve already discussed the types of paperboard typically used in blister packaging, but the type of paper isn’t the only variable. For instance, what is the caliper of the paper? The actual thickness of paper, typically measured in thousands of an inch, is the paper’s caliper. When two cards are used to hold thermoform plastic film, the caliper for each board piece can be as low as 12-point or as high as 24-point. So it’s necessary that the coating company qualify the paper grade and supplier to make sure the adhesive package works through the whole process.
- How will the card stock be printed? Different types of projects require different types of delivery to the commercial printing facility. Will the coated card stock be delivered in rolls? How will this affect the coating? Or will it be delivered in sheets? Will the stock need to be die cut, and if so, will it be via a rotary or platen die-cutting process? The efficiency of the printer and packaging company is dependent on the quality of the raw material that they choose to fulfill the job.
How Important Is Recyclability?
Green manufacturing and sustainability are becoming more and more important to consumers and retailers alike. In fact, Walmart has a scorecard that rewards products that use recycled materials, reduced packaging, or packaging that can be easily recycled. Opting for a blister card approach versus a clamshell can help boost recyclability by decreasing the amount of plastic used. Nearly all paper companies produce papers with pre-consumer or post-consumer recycled content. Card stocks made with recycled content can be hard to work with. However, some specialized coatings and laminations can help reduce these problems by improving the quality of the printing surface.
In addition, some of the latest blister coatings are more environmentally friendly than others, with lower to no volatile organic compounds and other Environmental Protection Agency-regulated attributes.
What Testing Procedures Ensure the Highest Quality and Performance?
Of course, just as important as careful planning when determining which blister card coatings are most advantageous is testing to make sure they work as desired. At the very least, a prototype should be given a squeeze test to make sure the plastic film’s adhesion to the blister card stock, or the adhesion of card stock to card stock, is sufficient to withstand normal handling wear and tear and, of course, transit conditions. Ideally, several more tests should be administered, such as testing the tear strength of the blister card, hot and cold blister adhesion resistance, transit method harmonics (vibration), and lastly, an inspection of the quality of the print surface, which is paramount to the success of any packaging run. That’s it for this edition; see you next time.
Tom Weber is president of WeberSource LLC and is AICC’s folding carton and rigid box technical advisor. Contact Tom directly at firstname.lastname@example.org.