What is Blister Packaging?
Blister packaging, or blister packs, are pre-formed packaging materials composed of a thermoformed plastic cavity and a pliable lid. In this type of packaging, the product is placed in deep-drawn pockets or cavities resembling a blister. A backing material, or lidding mates to the flat area of the plastic cavity enclosing the product inside, and A heat seal bonds the two structures. Blister packaging has various types depending on the application. The most popular use of blister packs is for packaging pharmaceutical products such as pills, tablets, capsules, and lozenges. Because of its low cost, cheap raw materials, and high operating speed, they are also used for packaging consumer goods such as foods, electronics, toys, and tools. Enumerated below are the benefits of using blister packaging.
Advantages of Blister Packaging
- Individual Packaging:
The first notable use of blister packs was for packaging birth control pills. Blister packaging is a cheap and convenient way of packaging individual doses of a drug. Also, the packaging can be marked to aid effective administration. Individual packaging helps maintain the quality of the contents through containment in separate cavities or pockets. Damage to any part of the packaging material will not affect the whole
- Maintaining Product Integrity:
Forming films and lidding structures are created according to the sensitivity of the product to moisture, oxygen, and light. The packaging components can be laminated with barriers that block the penetration of external elements. Opaque materials such as aluminium block light, preventing product degradation through UV radiation.
- Tamper Protection:
Blister packs, when opened, cannot be returned to their original form. Blister packaging has an inherent tamper-evident mechanism since it is impossible to separate the lidding to the blister card without causing visible damage. This helps deter package pilferage not only in pharmaceuticals but also in consumer goods such as electronics.
- Preventing Accidental Drug Misuse:
Blisters and lidding structures can be designed so that they cannot be opened easily without following instructions specified by a manufacturer. This prevents children, and even seniors, from accidentally taking the drug. This design is known as child-resistant (CR) packaging
- Visibility of Product:
Blister packs and skin and clamshell packaging are also used for retail products since they allow consumers to see the product through the packaging. In addition, the lid or backing material is coloured and designed to attract prospective buyers
- Minimal Movement Within Packaging:
It is easy for blister packs to take the shape of the product. The product‘s shape can be fed through a computer-aided machining program that controls a milling machine for creating a mould. The mould can be prepared to factor in only small clearances between the product and the packaging.
The Blister Packaging Process
The packaging process starts by designing the packaging format. Next, the manufacturer fabricates a negative die according to the shape of the product. A metal stock is milled with an array of cavities to prepare the negative die using a CNC machine. The die is then installed into the forming machine.
The forming process can either be thermoforming or cold forming. Plastic films such as PVC are processed by thermoforming, while laminated aluminium forming films employ cold forming. For thermoforming machines, a preheating process is done at temperatures below the plastic's melting point. As the film moves through the machine, it is formed to shape by air pressure (thermoforming) or by pressing a positive die (cold forming).
Meanwhile, before packaging, the products are visually inspected in a staging area. Then, the products are placed manually or automatically into the pocket for consumer goods. A packaging machine with hopper feeding is used for products with smaller profiles but large volumes, such as medicine tablets. The products are loaded into the hopper and then carefully fed into the pockets of the blister sheets. Brushes and paddles help disperse and arrange the product through the whole blister card.
The product then moves into the inspection station. Here, an inspector or visual sensor checks any damaged or broken items and marks them for rejection at the end of the packaging line. After inspection, the sheets are transferred into the sealing station.
Before sealing, a cylinder with embossed texts or graphics prints on one side of the lidding before being fed into the machine. The cylinder picks up the ink and then presses it onto the lidding film. At the sealing station, the lidding film and the blister sheet meet by pressing them against each other. Heat is applied to re-activate the sealing resin creating a bond between the two substrates. After bonding, the sealed blister packs are transferred into a cooling station that sets the bond.
The sealed blister sheets are then transferred into a trimming station where whole blister packs are cut into blister cards. Additional cuts are made by the machine depending on the intended application, such as child-resistant packs. Afterwards, the blister cards pass through a conveyor system, where an automatic rejection system removes flagged items from the packaging line. The conveyor leads the blister cards through robotic arms that automatically collect and place them into boxes or larger packs.
Components of Blister Packaging
There are four main components involved in blister packaging. These are the forming film, lidding, heat-seal coating and prints. The forming film and lidding are the main structural components that account for almost the total weight of the packaging. The heat seal layer creates a bond between the two structures. Lastly, the labels, batch numbers, codes, and other important information are added by printing.
- Forming Film in Blister Packaging:
The forming film creates the cavity. The forming film's selection depends on its properties, grade, and thickness. The cavity has the contour of the product with a slight clearance to allow for small deformations that could potentially damage the product. For the filming film to have the correct rigidity, it must be the right grade, have the proper thickness, and allow for convenient and easy opening.
- Backing Material or Lidding:
The lidding secures the product into the cavity. Classifications of lidding structures are divided into Push-Through-Packs (PTP), peelable lids, or a combination of both. PTPs are designed to be broken or torn while pressing into the pocket, as seen in typical medicine packaging. Lidding can also be made peelable without deforming the pocket, as seen in most consumer goods packaging. Push-peel lidding types are specially designed to be opened by performing a sequence of actions. These proprietary lid types are used for medicines for seniors and children, known as child-resistant blister lidding.
- Heat-seal Coating:
Heat-seal coatings bind the plastic blister pack and the lidding together. They are molten, or liquid polymer resins applied on the lidding material's surface using roll coaters, knives, gravure, brushes, or sprays. The right amount must be applied to create an air-tight sealing. After application, the resin is allowed to dry on the surface of the foil. This resin will be reactivated once the bonded foil-seal coat film is used for packaging.
- Prints in Blister Packaging:
Prints are added to the lidding structure to provide product information and attract buyers' attention. They are usually applied by flexographic printing. Since these are applied before the heat-sealing process, they must withstand the heat-sealing temperatures of about 572 ° F (300°C).
Types of Blister Packaging
The keys to the different types of blister packaging are the blister, cavity, box, and shape, which differ depending on the product to be packaged. The various substrates, materials, and heating sealing methods further separate the types of the products to be packaged, their sizes and shapes, defining the packaging method.
The four types of packaging methods are divided into plastic and paper, plastic with plastic, aluminium foil and plastic, and aluminium foil and aluminium foil.
- Clamshell Packaging
Clamshell packaging consists of an external shell with two similar-sized parts connected on one side. It gets its name from its appearance when it opens, which is similar to that of large clams in the ocean. Clamshell packaging comes in multiple sizes and is made from several different plastics. They are used in the fast-food industry as a replacement for boxes.
- Plastic and Paper Packaging
Plastic and paper blister packaging is known as blister cards or face seals and is a very common type of blister packaging. The plastic material is heated and shaped to the dimensions of the product, after which it is heat-sealed to a piece of cardboard.
- Trapped Blister Packaging
Trapped blister packaging is an innovation designed to replace the use of face seal blisters and clamshell packaging. It is a process that is similar to plastic and paper blister packaging. Unlike the plastic and paper method, where a sheet of plastic in the shape of the product is attached to a piece of cardboard, the trapped blister packaging method places the product, enclosed in plastic, between two pieces of cardboard.
- Plastic and Plastic Packaging
Plastic and plastic blister packaging is mainly a form of clamshell-style packaging that consists of a single piece moulded container that makes a plastic casing, which cannot be easily opened when sealed and closed. As a backing, plastic and plastic blister packaging has a piece of paper or cardboard placed inside or outside the casing for decoration and information. Plastic and plastic blister packaging allows customers full visual access to a product without having to open the package.
- Aluminum Foil and Plastic Packaging
Aluminium foil and plastic blister packaging have the same structure as plastic and paper blister packaging, where plastic is shaped to the form of the product. Instead of the backing being a piece of cardboard, in aluminium foil and plastic blister packaging, the backing is a piece of aluminium foil. It is an ideal packaging for medicines because it allows for easy accessibility but is an excellent sealing material
- Aluminum Foil and Aluminum Foil Packaging
In aluminium foil and aluminium foil packaging, both the front and back of the packaging are aluminium foil such that customers are unable to see the product. In some cases, the contents may be wrapped in sheets of plastic. Aluminium foil and aluminium foil packaging are seldom used due to their cost of manufacturing. Its purpose and development are for light-sensitive products that are protected by opaque aluminium foil.
- Slide Blister Packaging
Slide blister packaging is a variation of paper and plastic blister packaging where plastic in the shape of the product is attached to a piece of cardboard that completely encases the product. The variation of slide blister packaging is that it has flanges that wrap around the sides of the cardboard with an opening on one side that does not have a flange, which allows the piece of cardboard to slide in and out.
Conclusion
- Blister packaging, or blister packs, are pre-formed packaging materials composed of a thermoformed plastic cavity and a pliable lid. In this type of packaging, the product is placed in deep-drawn pockets or cavities that resemble a blister.
- Blister packaging offers the following benefits: individual packaging, maintaining product integrity, tamper protection, preventing accidental drug misuse, visibility, and allowing minimal movement within the packaging.
- Contract packaging is the process of outsourcing the packaging process to specialized service providers. This enables the manufacturer to focus on its operation and business process.
- There are four main components involved in blister packaging. These are the forming film, lidding, heat-seal coating and prints.
- Two main methods are used in foil forming: thermoforming and cold forming. Thermoforming is used for polymer-based materials, while cold forming is for laminated aluminium.
- PVC is the main material used for blister packaging; however, it is now being replaced due to its negative effects on the environment.
