Blister packs encompass a broad grouping of preformed thermoplastic packaging consisting of semi-rigid plastic shells. These forms may consist of two plastic sides sealed together, as with clamshells, or may be backed with cardboard or foil as needed to best suit a given application.
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Applications of Blister Packs
Blister packs are commonly used in these industries:
- Food and Beverage
- Sporting Goods
Extremely diverse, these beneficial packaging materials are clear, allowing the protection and display of such diverse items as toys, capsules, craft supplies, hardware, and electronics. Single-use or single dose pharmaceuticals, such as contact lenses and pills, are also commonly packaged in this way, as it provides clear dosing amounts and instructions with a protective and sterile barrier. The airtight seal on blister packs also improves the shelf life of food-based and medical products and creates a tamper-resistant and tamper-evident closure for consumer safety. Blister packs may be individual or conjoined to form what is known as a blister card. Other names for blister packs include blister strips and bubble backs.
Manufacturing Process of Blister Packs
One of the most frequently employed vacuum formed plastic products, blister packs can be produced through vacuum molding, thermoforming, or pressure forming as needed. Each technique involves an assembly line known as a blister line, which performs a series of processes.
In general, vacuum forming begins with a plastic sheet from a roll or extruder. This is fed into a pre-heating stage that uses electric, infrared, or natural gas heaters to warm the sheet to the temperature at which it becomes soft and pliable. The warm sheet is then guided into a form station where it is pressed into a mold, usually the inverse of the product to be contained. A vacuum is used to pull the material into the mold, while the material is cooled back to a rigid state. Reverse airflow may be used to break the vacuum hold and eject the newly made form, which then undergoes trimming and coating as needed. Cold forming may also be used in the manufacture of blister packs, though it is more expensive and time consuming as compared to the aforementioned molding methods, so it is used infrequently.
In any event, backings of cardboard and foil are applied with the use of strong adhesives while plastic sheet backings are welded or heat sealed to the form once the product has been properly placed. The type of plastic sheet from which these singular or conjoined units are constructed is most commonly clear polyvinyl chloride or PVC. This may be coded for added moisture resistance, though alternative materials, such as PCTFE and COC, may instead be used when these qualities are desired.