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Blister Carded Packages


By Francis Butler National Sales Manager Alloyed Company Incorporated


Rigid blister packaging offers product visibility specifically for self-service retailing.  Carded blisters meet the needs of this merchandising technique by offering prolonged shelf life and protection against moisture, dust, infestation, pilferage and breakage. It also provides tamper evidence, product visibility and instructions for use.


Blisters are manufactured by thermoforming. A plastic sheet is pre-softened by heating. Then is clamped over a mold, drawn into the mold by a vacuum, removed from the mold and cooled. Accurate tooling and molds are key to producing good consistent blisters of virtually any size and shape.


The basic components of a blister pack are the preformed plastic blisters; the heat-seal coating; the printing inks and the paperboard card.


1 Plastic sheet


Plastic sheet for blister packages is available in a range of grades and thicknesses. In selecting one, the packager must consider the size and weight of the products to be packaged, their value, their impact resistance and whether they have sharp or pointed edges. Heat-seal properties and the ease of cutting and trimming the formed blister must also be considered.


Rigid plastic sheet used for blister packages generally falls into three categories: cellulosics , styrenes and vinyls. Cellulosics are the most popular. They include acetate, butyrate and propionate. All three offer excellent clarity, superior thermoforming characteristics, good heat sealability and oil and grease resistance. The heat-seal temperature range of cellulosics is generally higher than that of the other films.


Oriented styrene offers excellent clarity but has low impact-resistance, shatters easily and performs poorly at low temperatures.  Impact styrene works well under these conditions.  Styrenes in general offer good heat sealability and clarity.


Vinyls, which are generally less expensive than styrenes, can be rigid or flexible. Vinyl heat seals well to properly coated paperboard.  It varies in clarity from excellent to good and in color from yellowish to slightly blue.  Plasticizer can be added to increase cold temperature resistance and impact strength.


2 Heat-seal coatings


The appearance and physical integrity of a blister depends heavily on the quality of the heat-seal coating which is applied to the face of the card.  Effective coatings offer good gloss, clarity, abrasion resistance and hot tack.


Hot tack (adhering properties achieved at high temperatures) is particularly important because when packaged products are ejected from the heat-seal jig, the entire weight of the package must be supported by a still warm adhesive bond line.


Also, a coating of proper weight must be applied to the paperboard card to achieve optimum heat seals. The coating must be compatible with the card and blister.  A relatively low heat-seal temperature is desirable for rapid sealing and prevention of blister-film distortion.


The most widely used coatings for blister cards are solvent-borne vinyls.  These lacquers have excellent gloss and abrasion resistance.  Water-borne acrylics are gaining ground but require somewhat more care in coating application; to achieve optimum appearance.


Printing inks may be applied to paperboard by letterpress, gravure, offset, flexography or silk screen.  Inks must resist high heat-sealing temperatures, abrasion, bending and fading and be safe for use with the products in the packages.


They should not contain excessive amounts of waste, hydrocarbon lubricants, greases, oils or release agents.


Paperboard is the main structural component of the carded blister pack.  It is selected according to the size, shape and weight of the product to be packaged.  Paperboard for blister packaging ranges in caliper (or thickness) from 0.014 to 0.030 inches, with 0.018 to 0.024 inches being the norm.


Paperboard must have a surface suitable for printing by the process and ink in use and be compatible with the heat-seal coating process.  It should withstand the stresses of printing (primarily causing delamination on offset) and still provide good fiber-tearing bonds when heat sealed to the plastic blister.


The backer card may be either recycled stock or solid bleached sulfate (SBS) board.  Generally speaking, SBS provides a more attractive package because of its clean white surface and the fact that it accepts inks readily.  If cost is a consideration, recycled paperboard can provide savings.


Through advanced thermoforming equipment and creative designs, suppliers of blister packaging have produced items such as cardless clamshells, reclosable reusable blister packages, hinged packages and multi product kits.


Blisters have upgraded pharmaceutical packaging, too.  A multiple blister sheet covered with foil allows the tamper-evident, push-through dispensing of pills or tablets.  This package, with individual protective blister compartments, offers an economical replacement for conventional glass and plastic bottles.


Skin Carded Packages


By Burton T. Spottiswoode Skin Packaging Industry Manager Polymer Products Department Du Pont Company


Skin packaging involves placing a product on a substrate material such as paperboard or corrugated and drawing heated plastic film down tightly to the board and around the product to make a secure, attractive package.  The product itself becomes the mold over which the heated plastic film or "skin" is drawn.


Skin packaging is used in two ways. For visual carded display, skin packages are typically rack hung, and are a cost-effective alternative to blister packs, five-panel cartons, fold-over cards and rack-hung thermoforms.  Costs are reduced because no tooling is needed to make blisters, no mold change over is needed and significantly reduced film gauges are common. Throughput may be faster or slower than alternative methods depending on the product size, configuration and volume.


A recent development in carded display packaging is high speed (10-30 cycles per minute), fully automatic machinery. Thermoform-fill-seal equipment, along time standard for food packaging and medical device packaging, has been modified by several manufacturers to run standard skin packaging mastercards or paper roll stock. These systems lend themselves to automatic product placement, making them competitive with other high-speed systems. In addition, several manufacturers of traditional skin-packaging machinery have introduced high-speed systems, making such equipment more attractive to high-volume users.


Also common is industrial skin packaging to protect products in transit.  Products as divergent as computer tapes, lamps, service repair kits and table tops may be skin packaged instead of using die-cut corrugated, foam-in-place, foam peanuts and other stabilizing or dunnage materials. Skin packaging offers high throughputs and full visibility, usually at significant savings.


Polyethylene and ionomer are the most commonly used skin-packaging films.  Recently, however, experiments have been conducted with co-extruded films combining these two materials or copolymers.  There may be film-cost advantages with co-extruded films, however, there is generally a sacrifice of strength and appearance vs. traditional films. While some co-extruded films have been developed for adhesion to unprimed paperboard, extreme caution must be used with respect to paperboard over time. Such materials may offer more value-in-use for industrial skin-packaging applications using unprinted, unprimed corrugated.


Some skin-packaging films may provide a fiber-tearing bond to unprimed, unprinted corrugated. However, the long-term adhesion under varying conditions has not yet been determined.  Since inks bring a third dimension to the system, adhesion to printed, unprimed paperboard is not yet recommended.


Improper ink or board-ink combinations can interfere with film-to-board adhesion, either chemically or physically. Pre-production ink tests are important to evaluate the compatibility of the ink system with the board and film. Generally, proofs are prepared by the printer using the ink and board specified.  Sample skin packages are made with these proofs to check for proper evacuation of air and adhesion.


The board is generally either a Fourdrinier (solid bleached sulfate), cylinder (non-bending chip, vat-lined or patent coated) or corrugated. Board must be selected for its thickness, stiffness, porosity and ability to support the product being packaged. Paperboard is most commonly 0.018 to 0.025 (but up to .054) caliper, while corrugated is usually 200 pound-test minimum.


Board, ink and primer are considered together because they combine to form a compatible, porous, strong and attractive system that becomes the backbone of the skin package. Clay-coated paperboard is usually not used because of its lack of porosity. Porosity also may be decreased by certain inks and heat seal coatings. If lower porosity paperboards are used, they must be perforated to increase air flow to ensure proper vacuum draw-down during heat sealing.


Skin packaging for visual carded display offers a number of benefits. The packaging operation is quick and uniform, the film's clarity and sparkle enhance the item and the display method spurs impulse buying because of product visibility and a large exposed graphics area.  Skin packaging also is ideal for multiple units on a single card. The backing card may reduce pilferage of smaller items that could be concealed if not mounted on a card.  Skin packaging is also tamper-evident.


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