Heat Seal Blister, Fold-Over, and Skin Card Packaging
Heat Seal Blister Packaging defines any of several types of pre-formed plastic carded packaging used to distribute small consumer products, such as foods, various goods, and pharmaceuticals. Importantly, blister packaging allows the consumer to see the product, reinforcing a purchasing decision.
A Blister Pack comprises a basic thermoformed plastic container and a paperboard card backing. A blister package is created when the formed container is heat-sealed to the paper-board card backing. This action captivates a product in the now-formed package. The key components are then, a printed, heat-seal coated paperboard card backing, and a thermoformed, flanged, transparent, plastic container (cell), or blister.
The unit is called a blister because it looks like a blister, rising above the backing board in its finished form. Blister packaging is used for a wide range of consumer goods, including hardware, electrical items, toys, pens, etc. Card graphics and transparency inform the consumer.
A Fold-Over Card is another form of carded packaging. Designed as a double blister card, either a fold-over, or a two-part card, a printed card is backside heat-seal coated, and a die-cut opening (hole) is cut into one side of the card. The opening conforms to the shape of a flanged two-sided transparent, thermoformed blister container. When forming the package, a blister container is dropped into the hole.
Then the product is put into the blister, and the backing card is located. In this position, the entire card and blister is heat sealed together, securing theft protection. These carded packaging forms are versatile and find use individually packaging small-size, high-value, weighty, and complex-shaped consumer products that are commonly displayed hung on a peg.
A Clamshell is another form of blister packaging and is known as a hinged blister. It consists of a single hinged thermos-formed transparent, blister cell. Edge heat sealing-fusing of the hinged folded-over-itself unit provides a secure seal. Completing a package, an informational card is inserted inside along with the product. A clamshell blister package is often used as a pilferage safe, and security package for high-value items with flange cutting needed to open.
Blister Container Components
Blister containers are molded from polyvinyl chloride (PVC), polyethylene terephthalate (PET), and other moldable plastics. PVC has the advantage of being low-cost, and easy to thermoform, but poor moisture and oxygen barriers are a disadvantage. PVC used in blister packaging is plasticizer-free to be rigid and strong.
PVC is sometimes coated with PVDC or laminated to PCTFE, or COC to improve barrier properties.
A form of blister packs is commonly used to provide unit-dose packaging for pharmaceutical pills tablets, capsules, and lozenges, etc. These heat-sealed units provide barrier properties, supporting shelf-life requirements.
In this application, a series of blister cavities are called alternately a blister card, a blister strip, or a blister pack. Differing, a strip pack does not have thermoformed or cold-formed cavities; but the strip pack is formed around the product (pill, tablet, etc.) at the time they are dropped into the sealing area between sealing molds.
The pharmaceutical blister pack is known as a push-through pack, as lidding foil allows the product to be pressed out breaking the lidding foil, or the semi-rigid formed cavity, being collapsible, allows dispensing with thumb pressure. Another variation uses peelable lidding foil to access a sealed product.
Skin Card Packaging
Skin Card Packaging is a form of carded packaging. A skin pack is formed when a product or products are secured to a heat seal-coated paperboard backing or tray by a transparent, formable plastic film. In assembly, the plastic film, such as LDPE, PET, ionomer, etc., is softened by heat and draped over the product located on the card/tray.
Vacuum applied to the backside of the card is used to snug the film down over the product for an intimate, heat-seal-adhered fit. The printed, heat seal coated paperboard/tray substrate, usually SBS, is of necessity porous. Other lesser porous substrates require pinhole perforating to allow vacuum-assisted airflow.
Once assembled a skin pack may be cut into smaller individual pieces, or units. A skin pack looks somewhat like a thermoformed blister pack except that the plastic skin is formed over the product. Fresh meat, fish, and poultry products are commonly skin-packed.
Heat Seal Blister Coatings
Heat seal blister coatings are a key component of producing functioning blister packaging. Heat sealing is a combination of temperature, time, and pressure. To be effective, activation at low temperatures is a necessity. Sealing heat driven through the backside of blister paperboard, which is an insulator, means the thicker the stock the higher the sealing temperature required.
At the same time, the blister coating cannot block during die-cutting or when cards are stacked awaiting use. Also, there is the risk of blocking any time extremely hot, humid warehouse and transport conditions are encountered. Blister coatings must also maintain good seals under the stress caused by weighty contained products when extremes of heat and cold are encountered during distribution and retail merchandising.
Blister board is a specially produced solid bleached sulfate (SBS) paperboard stock of low density that is designed to provide good fiber tearing bonds when effectively sealed to a plastic blister cell. These stocks are print-side clay coated (CIS) to accept various types of printing and heat seal coating. Stocks recommended for fold-over cards are clay-coated on both sides (C2S). Using stocks other than blister board can result in bonds that are not fiber-tearing, or are weak failure-prone bonds.
Cork has been instrumental in developing heat-sealable, advanced aqueous polymeric blister coatings. These aqueous coatings offer great utility in that they run traditionally off-line on roller-coaters, and more importantly, improving productivity, run one-bump in-line, on blanket coating devices. In-line, one-bump aqueous blister coatings have driven great, profitable growth opportunities for sheetfed litho printers. Contact us for your next project!
