Thermoforming Blister pack is a term for several types of pre-formed plastic packaging used for small consumer goods, foods, and for pharmaceuticals. The primary component of a Thermoforming blister pack is a cavity or pocket made from a formable plastic, usually a thermoformed plastic. This usually has a backing of paperboard or a lidding seal of aluminum foil or plastic.
Unit Dose Packaging of Pharmaceuticals
Thermoforming Blister packs are commonly used as unit-dose packaging for pharmaceutical tablets, capsules or lozenges. Thermoforming Blister packs can provide barrier protection for shelf life requirements, and a degree of tamper resistance. In the USA, Thermoforming 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, Thermoforming 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 a blister pack. The difference between a strip pack and a Thermoforming 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 sealing moulds. In some parts of the world the pharmaceutical blister pack is known as a Push-Through-Pack (PTP), an accurate description of two key properties (1) the lidding foil is brittle allowing the product to be pressed out while breaking the lidding foil and (2) a semi-rigid formed cavity flexible enough to dispense the tablet or capsule by pressing it out with your thumb. The main advantages of unit-dose Thermoforming blister packs over other methods of packing pharmaceutical products are the assurance of product/packaging integrity (including shelflife) of each individual dose and the ability to create a compliance pack or calendar pack by printing the days of the week above each dose. Thermoforming 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 Thermoforming blister pack is created from rolls of flat sheet or film, filled with the pharmaceutical product and closed (sealed) on the same equipment. There are two types of blister machine design: rotary-type and platen-type.
Other types of Thermoforming 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 visually examine the product through the transparent plastic. The plastic shell is air pressure-formed around a mold so it can contain the item snugly. The card is 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 light enough so that the package can be easily opened (in theory). Sometimes, with large items, the card has a perforated window for access.
In the case of thermoforming, a plastic film or sheet is unwound from the reel and guided though a heating station on the Thermoforming blister machine. The temperature of the heating plates (upper and lower plates) is such that the plastic will soften and become pliable. The warm plastic will then arrive in a forming station where a large air pressure (4 to 8 bar) will form the blister cavity from a forming mold. The blister is cooled os that the plastic becomes rigid again and maintains its shape when removed from the mold. In cases of difficult shapes, the warm film will be physically pushed down partially into the cavity by a “plug-assist” feature. Plug-assist results in a blister cavity with more uniform wall distribution and is typically used when the cavity size and shape is larger than a small tablets.
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 offers a nearly complete barrier for water and oxygen, allowing an extended product expiration 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 cannot be formed with near 90 degree angles).
The most basic material for the forming web is PVC or Polyvinyl Chloride. The principal advantages of PVC are the low cost and the ease of thermoforming. The main disadvantages are the poor barrier against moisture ingress and oxygen ingress; moreover PVC has a negative environmental connotation due to its chlorine content. In the case of blister packaging the PVC sheet does not contain any plasticizer and is sometimes referred to as Rigid PVC or RPVC. In the absence of plasticizers, PVC blisters offer structural rigidity and physical protection for the pharmaceutical dosage form. On the other hand, the blister cavity must remain accessible by the push-through effect and the formed web may not be too hard to collapse when pressed upon; for this reason the PVC sheet thickness is typically chosen between 200μ to 300μ depending on the cavity size and shape. Most PVC sheets for pharmaceutical blisters are 250μ or 0.250 mm in thickness. In order to overcome the lack of barrier properties of PVC film, it can be coated with PVDC or laminated to PCTFE or COC to increase the protective properties. Multi-layer blister films based on PVC are often used for pharmaceutical blister packaging, whereby the PVC serves as the thermoformable backbone of the structure. Also, the PVC layer can be colored with pigments and/or UV filters.
*The above information is provided by Wikipedia
Jornen Machinery Co., Ltd. 2012/11/27