Blisters: We use them every day or very often. Better to know more!

The blister is a type of plastic packaging pre-built and used to contain small objects. Thanks to its characteristics of lightness, manageability and protection of the contents, blister packs are often used as single-dose containers of medicines. But that’s not all.

Blisters are mainly made up of two components:

• The cavity which is made of a deformable material, such as plastic and aluminium, and is obtained by heating the deformable material in the factory or by mechanical means. Usually, the cavity contains the product packaged through the use of thermoforming machines. At Farmo Res, for example, we have built two dedicated machines: the BLISTERPACK K7.360 and the KBS260x330ND;
• the lid, which can be made of paper, plastic or breakable aluminium. On the lid there is information about the manufacturer and the content, especially for medicines.

The blister is opened by pressing a finger against the deformable cavity that, breaking through the lid, pushes out the product.

The importance of blisters in the packaging of pharmaceutical products

Blister packs are real units of measure for pharmaceutical tablets, pills and other medicinal products. Their use guarantees:

• the integrity of the product, which is guaranteed by the extreme difficulty of tampering with the product contained in the cavity after packaging. Tampering with the blister would in fact mean irreparably breaking the lid of the blister;
• the possibility to view the product and check the doses taken and those still inside the package;
• the ease and speed of opening the package without excessive effort;
• easy writing and marking of the expiry date of the product and other useful and/or legally required information.

In the pharmaceutical sector, blisters with speciality medicines are produced by the same pharmaceutical company that will use them or by a designated company, filled with their medicine and closed by a single, same, machine. This process, in technical jargon, is called blistering.

Always speaking of the pharmaceutical field, the most used material for the production of blisters is PVC or polyvinyl chloride. The main advantages of PVC are the low cost and the possibility of using production at high temperatures. PVC, on the other hand, forms a weak barrier to moisture and oxygen and, due to its chlorine content, is not entirely “green”. In the case of pharmaceutical blisters, PVC must not contain any plasticizers and is sometimes referred to as rigid PVC or RPVC. In the absence of plasticisers, blisters offer good structural rigidity and physical protection for the pharmaceutical doses contained; however, as they should allow easy expulsion of the medicinal product, the thickness of PVC used will be between 0.2 and 0.3 mm.

Other areas of application for Blister packs

Other uses of the blister are found in the packaging of common products, such as toys, toothbrushes, cosmetics and hardware components. They are also very common in the children’s sector as they are used for the packaging of children’s accessories such as soothers, rubber dummies and teats. In addition to perfect product packaging, the convenience of blister packing is that the customer can easily view the contents through the blister cavity made of transparent material, commonly PVC.

Shell Blisters

They are very special blisters used to prevent the opening of the package, especially used to contain products of reasonable value small enough to be stolen by hiding them from the sight of the staff of the stores. Used mainly for video games and electronic materials, shell blister packs consist of two suitably shaped PVC parts that are fused together to produce a durable package that cannot be opened by hand, but only with the help of scissors or other cutting tools.

Ways to produce blisters

• Through high temperatures. When blister packs are produced at high temperatures, a plastic film wrapped on a reel is unwound and conveyed into the blister pack into a “preheating station” where it is heated to a temperature that varies according to the material used, where the plastic becomes malleable. The hot plastic is then conveyed to a second station where, through a high pressure mould (between 4 and 8 bar), it imprints the various cavities. After this operation the plastic is cooled and the mould removed, so that the shape remains imprinted on the film.
• Cold process. In the case of cold production, an aluminium-based film is pressed onto a mould. These blisters are called CFF (cold form foil) in technical jargon. The advantage of using CFFs is the use of aluminium, which offers complete protection of the content from water and oxygen. The disadvantages are the lower production speed of the blisters compared to those produced by high temperatures, the loss of transparency of the pack and the size of the blister pack, because the aluminium cannot be deformed at angles approaching 90°.