What Is Blister Packaging?
Most people have bought products that have come sealed in a plastic casing at some point or another. Some common examples are cosmetics, pharmaceuticals, toys, hardware, electronic and computer devices. Blister packaging is the technique used to package these kinds of small products. This type of pre-formed packaging forms a mold around the product to protect it during shipping and keep the product safely contained until it reaches the consumer. The two primary components of a blister pack are the cavity made from either plastic or aluminum with the lidding made from paperboard, paper, plastic or aluminum. The cavity is where the product is contained snuggly and the lidding seals the product to form the package. The backing card usually has some featured artwork on it and a clear plastic pocket known as the blister used for placing addresses and name details. The clear plastic window allows customers to view the contents of the item prior to purchase.
Products That Use Blister Packaging
When used for pharmaceuticals, a series of blister cavities is sometimes called a blister card, blister strip or blister pack. The difference between a strip pack and blister pack is that a strip pack doesn’t have thermo-formed or cold formed cavities. The strip pack is formed around the tablet when it is dropped to the sealing area between molds. Medical blister trays differ from Pharmaceutical blister packs in that they are not push-through packs. They are designed for medical devices used in hospitals. The thermoformed base web is made of a thicker plastic sheet and can not be collapsed, thus forming a solid tray. The lidding film provides a peel-open feature and is generally porous to allow sterilization.
Toys, Hardware, Electrical Devices
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.
Another kind of blister is a blister card where a plastic shell is vacuum-formed around a mold so it can contain the items snugly. The card contains a design suited to the product inside and plastic is affixed to the card using heat and pressure to create a heat sealed coating on the blister card. The adhesive is strong enough so the pack is able to hang on a peg but still allow the package to be easily opened. The card has a perforated window for access with large items.
A hinged blister is known as a clamshell used often as a security package for small high value items that have a high theft rate such as consumer electronics. It consists of one sheet folded over to the other other side and sometimes fused together at the edges. They can be securely heat sealed make them difficult to open by hand to deter tampering. A sharp device such as scissors or a knife is required to open them.
Types Of Materials Used In Blister Packaging
Materials used for blister packaging vary depending on what is being packaged in the casing. Plastic is used most, Thermoformed plastic being the most common. Paper, cardboard and aluminum are other materials used in blister packaging and can be tailored to the needs of a certain product and client’s budgetary requirements.
Poly Vinyl Chloride (PVC) is the third most widely produced plastic after polyethylene and polypropylene and the most basic material for forming web. PVC is low cost and is easy to use in thermoforming, however, by itself is a poor barrier against moisture ingress and oxygen ingress and has a negative environmental connotation due to its chlorine content. In the case of blister packaging, the PVC sheet doesn’t contain any plasticizer and is sometimes referred to as Rigid PVC or RPVC. With the absence of plasticizers, PVC blisters offer structural rigidity and physical protection for the pharmaceutical dosage form. The blister cavity must remain accessible via the push-through effect and the formed web may not be too hard to collapse when pressure is applied. The proper PVC sheet thickness chosen helps to address this issue. Mult-layer blister films based on PVC are often used for pharmaceutical blister packaging where the PVC serves as the thermoformable backbone of the structure. The PVC layer can be colored with pigments and/or UV filters. The PVC formulation is made to comply with the US Pharmacopeia requirements.
Polychlorotrifluoroethylene (PCTFE) is a material that can be laminated to PVC to obtain very high moisture barrier at varying structural levels. Cyclic Olefin Copolymers (COC) or polymers (COP) can provide provide moisture barrier to blister packs in multilayered combinations with polypropylene (PP), polyethylene (PE) or glycol-modified polyethylene terephthalate (PETg). Cyclic olefin resins are generally amorphous and noted for good thermoforming characteristics even in deep cavities making it popular for the use of COC in blister packaging as a thermoforming enhancer, especially in combination with semicrystalline resins such as PP or PE. Films can be manufactured via coextrusion or lamination. Unlike PVC and other common pharmaceutical barrier resins, cyclic olefin resins do not contain chlorine or other halogens in their molecular structure and are composed solely of carbon and hydrogen. They are made to comply with guidelines in the US, Europe and Japan.
How Is Blister Packaging Made?
There are two special machines designed to make blister packs: rotary and flat-plate. In the case of thermoforming, a plastic film or sheet is unwound from the reel and guided through a pre-heating station on the blister line. The temperature of both upper and lower pre-heating plates is hot enough to soften and make the material pliable. The warm plastic then arrives in a forming station where a large pressure made by a bar will form the blister cavity into a negative mold. The mold is then cooled until the plastic becomes rigid and maintains its shape when removed from the mold. A plug assist feature is used for difficult shapes to create more uniform wall distribution.
When using the cold forming process, an aluminum-based laminate film is pressed into a mold by a stamp. The aluminum is elongated but still maintains the formed shape. These blisters are referred to as cold form foil (CFF) blisters. The main advantage of cold form foil blisters is that the use of aluminum offers near complete barrier to water and oxygen that extends a product expiration date. Cold form foil blisters are produced at a slower speed compared to thermoforming and lack transparency in the packaging. Also, the larger size of the blister card prevents aluminum from forming with near 90 degree angles.
Advantages of Blister Packaging
Blister packs are useful for protecting the product against external factors such as humidity and contamination for extended periods of time. Opaque blisters are specifically designed to protect sensitive products against daylight. Blister packs can be used as unit-dose packaging for pills, capsules or lozenges because it can provide barrier protection to meet shelf life requirements and tamper resistance needs. Unit-dose blister packs assure the packaging integrity of each dose and are created by means of a form-fill-seal process at the 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 sealed on the same equipment.
Even if a blister package experiences a blister dent, or dented bubble, the product is still protected from damage due to the type of packaging.
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