Blister packs encompass a broad grouping of pre-formed 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. Though mainly used in packaging, the design of blister packs makes them popular in a number of manufacturing and retail industries.
Not just design, but price and a high strength to weight rations make blister packs popular in the following industries: food and beverage, sporting goods, electronics, medical, appliance, automotive, cosmetics and telecommunications. 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 improves the shelf life of food based and medical products and also 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 commonly include blister strips and bubble backs.
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 which is fed into a pre-heating stage which uses electric, infrared or natural gas heaters to warm the sheet to the temperature at which they become 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 is more expensive and time consuming as compared to the aforementioned molding methods and is therefore 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 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 such qualities are desired.
Blister Packs Informational Video