Definitions

blister-pack

Blister pack

Blister pack is a term for several types of pre-formed plastic packaging used for small consumer goods.

The two primary components of a blister pack are a pre-formed plastic blister and a printed paperboard card which has a heat-seal coating. Some packs use a foil, plastic or laminated material to bond to the pre-formed blister

Uses

Unit doses of drugs

Blister packs are commonly used as unit-dose packaging for pharmaceutical tablets, capsules or lozenges. Blister packs can provide barrier protection for shelf life requirements, and a degree of tamper resistance. In the USA, blister packs are mainly used for packing physician samples of drug products, or for Over The Counter (OTC) products in the pharmacy. In other parts of the world, blister packs are the main packaging type since pharmacy dispensing and re-packaging are not common. A series of blister cavities is sometimes called a blister card or blister strip as well as blister pack. In some parts of the world the blister pack is known as a Push-Through-Pack (PTP). Main advantages of unit-dose blister packs over other methods of packing pharmaceutical products are the assurance of product/packaging integrity (including shelflife) of each individual dose and the possibility to create a compliance pack or calendar pack by printing the days of the week above each dose.

Blister packs are created by means of a form-fill-seal process at the pharmaceutical company or designated contract packer. A form-fill-seal process means that the blister pack is created from rolls of flat sheet or film, filled with the pharmaceutical product and closed (sealed) on the same equipment. Such equipment is called a blisterline.

Blister packs consist of two principal components : 1) a formed base web creating the cavity inside which the product fits and 2) the lidding foil for dispensing the product out of the pack. There are two types of forming the cavity into a base web sheet: thermoforming and cold forming.

Consumer goods

Other types of blister packs consist of carded packaging where goods such as toys, hardware, and electrical items are contained between a specially made paperboard card and clear pre-formed plastic such as PVC. The consumer can easily examine the product through the transparent plastic. The plastic shell is vacuum-formed around a mold so it can contain the item snugly. The card is brightly colored and designed depending on the item inside, and the PVC is affixed to the card using heat and pressure to activate an adhesive (heat seal coating) on the blister card. The adhesive is strong enough so that the pack may hang on a peg, but weak enough so so that the package can be easily opened. Sometimes with large items the card has a perforated window for access.

A more secure package is known as a clamshell. Typically used for theft-prone items like consumer electronics, it consists of either two pre-formed plastic sheets or one sheet folded over onto itself and fused at the edges. They are usually designed to be difficult to open by hand so as to deter tampering and pilfering. A pair of scissors or a sharp knife is often required to open them. Care must be used to safely open some of these packages.

Production

Thermoforming

In the case of thermoforming, a plastic film or sheet is unwound from the reel and guided though a pre-heating station on the blister line. The temperature of the pre-heating plates (upper and lower plates) is such that the plastic will soften and become moldable. The warm plastic will then arrive in a forming station where a large pressure (4 to 8 bar) will form the blister cavity into a negative mold. The mold is cooled such that the plastic becomes rigid again and maintains its shape when removed from the mold. In case of difficult shapes, the warm film will be physically pushed down partially into the cavity by a "plug-assist" feature.

Cold forming

In the case of cold forming, an aluminum-based laminate film is simply pressed into a mold by means of a stamp. The aluminum will be elongated and maintain the formed shape. In the industry these blisters are called cold form foil (CFF) blisters. The principal advantage of cold form foil blisters is that the use of aluminum is offering a near complete barrier for water and oxygen, allowing an extended product expiry date. The principal disadvantages of cold form foil blisters are: the slower speed of production compared to thermoforming; the lack of transparency of the package (a therapy compliance disadvantage); and the larger size of the blister card (aluminum can not be formed with near 90 degree angles).

See also

References

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