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Blister packaging, commonly known as blister packs, consists of a pre-formed plastic cavity and a flexible lid. The product is placed in molded pockets or cavities within the plastic, which are then sealed with a backing material or lidding. This seal is typically achieved through heat bonding, securing the product inside. Blister packaging comes in various forms tailored to different applications. It is most commonly used in the pharmaceutical industry for packaging items such as pills, tablets, capsules, and lozenges. Additionally, due to its cost-effectiveness, use of inexpensive raw materials, and high production efficiency, blister packaging is also widely employed for consumer goods including food products, electronics, toys, and tools. The advantages of using blister packaging include:
Blister packs were first widely utilized for packaging birth control pills. This type of packaging offers an affordable and practical solution for dispensing single doses of medication. It also allows for clear marking to assist with proper administration. By containing each dose in separate cavities or pockets, blister packaging helps preserve the quality of the contents. Furthermore, damage to one part of the packaging does not compromise the integrity of the remaining doses.
The films and lidding materials used in blister packaging are selected based on the product’s sensitivity to moisture, oxygen, and light. To protect the contents, these components can be laminated with barrier layers that prevent external contaminants from penetrating. For instance, opaque materials like aluminum are used to block light, thereby protecting the product from degradation caused by UV radiation.
Once opened, blister packs cannot be resealed to their original condition. This type of packaging inherently includes a tamper-evident feature, as separating the lidding from the blister card results in visible damage. This built-in security helps prevent tampering and pilferage, making it an effective choice for both pharmaceuticals and consumer products like electronics.
Blisters and lidding structures can be engineered to require specific actions or instructions to open, making them difficult to access without proper handling. This design, known as child-resistant (CR) packaging, helps prevent accidental ingestion by children and also assists in avoiding unintended use by seniors.
Blister packs, as well as skin and clamshell packaging, are commonly used for retail products because they offer visibility of the product through the packaging. Additionally, the lid or backing material is often colored and designed to capture the attention of potential buyers.
Blister packs can be easily customized to match the shape of the product. By using computer-aided design (CAD) software, the product's dimensions can be programmed into a milling machine to create an accurate mold. This mold can be precisely engineered to accommodate minimal clearances between the product and the packaging.
Since packaging is often not a part of the production process, manufacturing plants often employ third-party services dedicated to the packaging process. Contract packaging is a service provided by packaging companies that usually comprises the supply of labor and equipment for product packaging. Contract packaging companies invest in sophisticated equipment such as blister packaging machines accredited by regulating bodies. This allows the manufacturer to focus its human resources and business process solely on production while benefiting from of a specialized packaging system. A contract packaging setup also enables more investment into quality testing of packaging raw materials impractical for manufacturing plants. In broader scopes, the packaging company is responsible for producing graphic materials and product manuals, controlling inventory, warehousing, and distribution.
The packaging process begins with designing the packaging format. The manufacturer then creates a negative die based on the product's shape. This involves milling a metal stock with an array of cavities using a CNC machine to form the negative die. Once completed, the die is installed into the forming machine for further processing.
The forming process can either be thermoforming or cold forming. Plastic films such as PVC are processed by thermoforming, while laminated aluminum 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).
Before packaging, products undergo visual inspection in a staging area. They are then either manually or automatically placed into the pockets designed for consumer goods. For products with smaller profiles but high volumes, such as medication tablets, a packaging machine with hopper feeding is employed. The products are loaded into the hopper, which then feeds them into the pockets of the blister sheets. Brushes and paddles assist in distributing and arranging the products throughout the blister card.
Next, the products move to the inspection station where an inspector or visual sensor identifies and marks any damaged or defective items for removal at the end of the packaging line. Once inspected, the sheets proceed to the sealing station.
At the sealing station, a cylinder with embossed text or graphics prints on one side of the lidding film before it is introduced to the machine. The cylinder transfers ink onto the lidding as it presses against it. The lidding film and the blister sheet are then brought together, and heat is applied to activate the sealing resin, forming a secure bond between the two layers. After sealing, the blister packs are directed to a cooling station to solidify the bond.
Once sealed, the blister sheets are moved to the trimming station, where they are cut into individual blister cards. The machine makes additional cuts as needed for specific features, such as child-resistant packaging. The blister cards then proceed along a conveyor system, where an automatic rejection mechanism eliminates any defective items. Finally, the conveyor system guides the cards to robotic arms, which automatically gather and package them into boxes or larger containers for distribution.
Operators select samples from the packaging line to conduct quality checks, particularly for pharmaceutical products. One common method is water submersion testing or blue dye testing. This leak test involves placing the blister card under a vacuum for a few minutes. If there is a defect in the seal or damage to the film, a vacuum forms inside the blister. The card is then submerged in water with dye. After removal, the packs are manually inspected for any visible issues. However, advancements in probing and scanning technologies have enabled automated visual inspections of finished blister packs. While the water submersion method has limitations, such as not covering the entire production, modern scanning and inspection systems can effectively examine each pocket and identify specific cavities with defects.
Blister packaging consists of four primary components: forming film, lidding, heat-seal coating, and printed information. The forming film and lidding are the key structural elements, contributing most of the packaging's weight. The heat-seal coating bonds these two components together. Additionally, printing is used to apply labels, batch numbers, codes, and other essential information to the packaging.
The forming film is responsible for creating the cavities in blister packaging. The choice of forming film depends on its properties, grade, and thickness. The film must be precisely matched to the product's contour with slight clearance to accommodate minor deformations without damaging the product. Proper rigidity is crucial: if the film is too rigid, removing the product can be difficult, whereas if it is too flexible, it may not adequately protect the product. The film must strike a balance to ensure both structural integrity and ease of access.
The lidding secures the product within the cavity and can be classified into several types: Push-Through-Packs (PTP), peelable lids, or a combination of both. PTP lidding is designed to be torn or broken when pressing into the pocket, commonly seen in medicine packaging. Peelable lids, on the other hand, can be removed without deforming the cavity and are often used for consumer goods. There are also push-peel lidding types, which require a specific sequence of actions to open. These are often used in child-resistant packaging for medicines intended for seniors and children.
Common lidding materials include aluminum foil, PET, paper, or combinations thereof. Aluminum foil, which can be either soft or hard-tempered, is frequently used. Soft-tempered aluminum foil is more malleable and suitable for packaging hard materials like tablets and lozenges. Its malleability allows for some deformation before breaking, making it ideal for child-resistant blister packaging by preventing children from easily pushing tablets out. Soft aluminum foils used in blister lidding typically have a thickness of 1.0 mil (1/1000th of an inch).
Hard-tempered aluminum foils do not elongate and can be torn easily with sufficient force. They are typically used for lids designed to be pushed through or peeled off. For a single-layer, hard aluminum lid structure, the foil thickness is approximately 0.8 mils. This type of structure is commonly used in push-through packs.
Hard aluminum foils can also be combined with paper and PET for child-resistant packaging that allows for various opening methods, such as pushing through, peeling off, or a combination of both. A common design involves peeling off the paper and PET layers first, followed by pushing through the tablet, which tears the aluminum foil.
Heat-seal coatings are used to bind the plastic blister pack and the lidding together. These coatings are molten or liquid polymer resins applied to the surface of the lidding material using techniques such as roll coating, knife coating, gravure, brushing, or spraying. The resin must be applied in the correct amount to ensure an air-tight seal. After application, the resin is allowed to dry on the foil's surface. Once the foil-seal coat film is used in packaging, the resin will be reactivated to form a secure bond.
Heat-seal coatings for blister packaging typically have several key characteristics: low-temperature activation, a low coefficient of friction, high gloss, and high transparency. For pharmaceutical and food packaging, the polymer resin must be approved by the FDA for direct food contact compliance. Common types of heat-seal coatings include solvent-based and water-based resins, such as polyvinylidene chloride (PVDC), acrylic, and ethylene acrylic acid (EAA). Additionally, extrusion-coated and co-extruded polyolefin films are used, including low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), and ethylene-vinyl acetate (EVA).
Product details and attractive designs are printed onto the lidding material to provide essential information and capture consumer interest. This is typically done using flexographic printing methods. As these prints are applied before the heat-sealing stage, they need to endure temperatures of approximately 572°F (300°C) during the sealing process.
Two main methods are used in foil forming: thermoforming and cold forming. The most common material used in blister packaging is PVC. PVC is formed by thermoforming, which makes the process widely used. For applications requiring better barrier properties, laminated aluminum is the better option, which is formed by cold forming.
Thermoforming involves heating thin plastic sheets until they reach a pliable state, then stretching them over a mold to achieve the desired shape. This method is widely used in blister packaging due to its straightforward process and efficiency in producing large quantities.
The process begins by placing the plastic sheet into a preheating station, where it is heated just above its glass transition temperature. This softens the plastic, making it flexible but not fully molten. The heated sheet is then moved to the forming station, where a die applies pressure to create the shape of the blister pack. Various thermoforming techniques are employed in blister pack production, with vacuum forming and pressure forming being the most prevalent methods.
In vacuum forming, the air is evacuated from the cavity that draws the heated film acquiring the profile of the die. Pressure forming, on the other hand, pushes the film into the cavity. For instances when the shape is difficult to form by air pressure alone, a plug-assist feature is used to push down the film into the die. This results in a more uniform wall thickness. After the forming process, refrigerated plates press against the formed films which set into their new shape. They are then trimmed to size using a die cutter.
This method is often utilized for packaging items that are sensitive to moisture and light. Instead of clear plastic films, cold forming employs thin polymer-aluminum laminates. These laminates typically consist of 1.8 mils of aluminum combined with 3 mils of polymer layers, effectively preventing water permeability. Unlike thermoforming, which uses heat to shape the film, cold forming involves mechanically pressing the film into a die. This process requires both a negative die and a positive plug, which can make cold forming machinery more costly than thermoforming. Additionally, cold forming cannot achieve sharp 90° angles, leading to the need for draft angles that increase the overall size of the blister. While the cost per meter of laminated aluminum is similar to that of plastic films, the reduced number of products that can be accommodated in a given area raises the material costs.
Blister packaging utilizes a range of materials, with PVC being a popular choice due to its affordability and simple shaping process. Nonetheless, there is a push towards alternatives to PVC due to its environmental impact. Chlorine and fluorine-based polymers can release toxic acids, leading to stricter regulations in many advanced nations. Below are some materials commonly used in the production of blister packs.
Blister packaging commonly relies on a variety of materials, with PVC being the most prevalent due to its cost-effectiveness and ease of shaping. PVC accounts for approximately 95% of the blister packaging industry. This material is characterized by its rigidity, as it lacks plasticizers or softening agents. Its robustness and clarity make it an excellent choice for product protection while also showcasing the item to potential buyers. Additionally, PVC films offer good barrier properties and chemical resistance. Typically, the thickness of these films ranges from 0.08 to 0.12 inches (0.2 to 0.3 mm). However, it's important to be aware that rigid PVC can degrade at high temperatures, a process known as dehydrochlorination, which releases hydrogen chloride. To mitigate this issue, stabilizers are added during the heating phase of PVC film production, and these stabilizers must be FDA-approved for applications involving food contact.
PVDC, while not used as a forming film on its own, is often coated onto other materials like PVC and aluminum to enhance barrier properties significantly, improving them by a factor of five to ten. PVDC coatings are notable for their ability to block both moisture and oxygen effectively. Additional advantages of PVDC include its heat-sealability, high gloss, transparency, and flexibility. These coatings are utilized not only on forming films but also on lidding materials. PVDC is applied to the side that comes into contact with the product. However, similar to PVC, PVDC can experience thermal degradation, releasing hydrogen chloride and raising environmental concerns.
This material is part of the fluoropolymer family and is known commercially as Aclar film, a trademark of Honeywell. Similar to PVDC, PCTFE (polychlorotrifluoroethylene) is applied as a laminate over PVC to improve barrier properties. PCTFE is renowned for its exceptionally low permeability to moisture and gases, as well as its resistance to aggressive chemicals, UV radiation, and ozone. Although not particularly strong or durable on its own, it offers excellent abrasion resistance. It is also noted for its transparency and superior thermal stability. Aclar film finds extensive use in military, electronics, and aerospace sectors, where it is employed in environments rich in oxygen and for packaging products stored in liquid nitrogen. In the pharmaceutical industry, Aclar laminates are ideal for aseptic blister packs due to their capability to withstand heat sterilization.
Polypropylene has emerged as an alternative to PVC for forming films. Its water vapor permeability is similar to that of PVC coated with PVDC. Polypropylene is often preferred in certain regions with strict regulations because it does not release harmful substances during incineration and is more recyclable compared to PVC. However, polypropylene poses challenges in processing; it is not easily compatible with standard blister packing machines. The thermoforming process for polypropylene requires precise temperature control due to its narrow operating range. Issues such as warping and shrinkage during post-processing can affect the overall quality of the packaging.
PET is another potential alternative to PVC. While polyethylene is commonly used for packaging food and consumer products, it is less favored for pharmaceutical blister packaging due to its higher water vapor permeability compared to PVC. Although adding a PVDC layer can mitigate this issue, it undermines the goal of avoiding the release of harmful gases.
COC, or cyclic olefin copolymer, is a group of fully amorphous resins valued for their similar properties to PVC but without its drawbacks. COCs with a multilayer configuration are particularly effective for blister packaging due to their low water vapor permeability. The characteristics of COC films can be adjusted by creating custom blends of polyolefins. This allows modifications in various properties, including elasticity, clarity, vapor transmission rate, and friction coefficient.
This type of film combines aluminum with PVC and either polyamide or polyester layers. These laminated aluminum films are formed through a cold-rolling process. They effectively block water vapor, making them ideal for medications that require extended shelf life. Additionally, they offer complete protection against light and oxygen.
Blister packaging varies based on the blister, cavity, box, and shape, all of which are tailored to the specific product being packaged. The choice of substrates, materials, and heat sealing techniques further distinguishes the types of packaging, influencing the product’s size, shape, and the overall packaging method.
Packaging methods fall into four categories: plastic and paper, plastic and plastic, aluminum foil and plastic, and aluminum foil and aluminum foil. Originally, blister packaging was created to securely seal medications in tamper-evident containers. Since its inception in the mid-20th century and through technological advancements, blister packaging has diversified across many industries, offering innovative solutions for product presentation and protection.
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 blister packaging, commonly referred to as blister cards or face seals, is one of the most widely used forms of blister packaging. In this process, the plastic is heated and molded to fit the product’s shape, and then it is heat-sealed to a piece of cardboard.
Trapped blister packaging represents an advancement intended to replace traditional face seal blisters and clamshell designs. This method shares similarities with plastic and paper blister packaging but differs in execution. Instead of attaching a plastic sheet shaped like the product to a piece of cardboard, trapped blister packaging encases the product in plastic between two layers of cardboard.
The trapped blister packaging method is favored for its cost-effectiveness and use of environmentally friendly materials. It provides a high level of security, making it difficult to open. This type of packaging has gained popularity, particularly in club store merchandising.
Plastic and plastic blister packaging is primarily used in clamshell-style designs, featuring a single molded plastic container that forms a secure, tamper-resistant casing. Typically, this packaging includes a piece of paper or cardboard either inside or outside the plastic shell for decorative purposes and to provide product information. This method offers customers complete visibility of the product without the need to open the package.
Aluminum foil and plastic blister packaging shares a similar structure with plastic and paper blister packaging, where the plastic is molded to fit the product. However, instead of using cardboard as the backing, this method employs a layer of aluminum foil. This type of packaging is particularly suitable for pharmaceuticals as it provides both easy access and excellent sealing properties.
Aluminum foil and aluminum foil packaging features aluminum foil on both the front and back, making the product invisible to customers. Sometimes, the product is also wrapped in plastic sheets. This packaging type is infrequently used because of its high production costs. It is specifically developed for products sensitive to light, as the opaque aluminum foil offers excellent protection against light exposure.
Slide blister packaging is a variation of paper and plastic blister packaging in which the plastic, molded to the shape of the product, is attached to a piece of cardboard that fully encloses the item. The distinguishing feature of slide blister packaging is the inclusion of flanges that wrap around the sides of the cardboard, with an open side without a flange. This design allows the cardboard to slide in and out easily.
Contract packaging involves putting a specific product into its completed packaging using a contracting business. It is also known as co-packing or co-packaging. A company can hire another business entity for the production of its packaging, product assembly and...
Thermoforming is the process of heating thin plastic sheets to its forming temperature and stretching it over a mold which takes its shape. After cooling and setting of the molded plastic sheet, each part will be separated from its batch to form a single unit or product...