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What is a Trapped Blister and How Does It Work?

How Trapped Blisters Work

Vitamin type bottle secured by a trapped blisterTo address this question, let’s use an example. In this case, the tablets are secured in the twist open bottle. With no further protection, the item can easily be tampered with or pilfered, creating liability and loss. The clear plastic “blister” covering the bottle will aid in protecting the contents from both tampering and theft, but the plastic blister needs to be secured. There are options to secure the blister and here we focus on the paperboard option.

Clear blisters with flangesCreating the blister requires a few considerations. First a mold is designed to conform to the shape of the bottle that holds the tablets. In this example anti-rotation features were added to the blister to keep the customer’s marketing information front and center. The anti-rotation design can vary to be as simple as an indentation in the blister to keep the placement of the item, or more complex, depending on the need.

The blister design includes additional plastic around the edge, known as the flange, which flows outward (by varying size) creating the part of the blister that will be functional to secure the item. This is one of the most important features of a trapped blister and the size of the flange is considered heavily in the design.

The next component of the trapped blister is the paperboard. In this example, the front has been designed to leave the opening for the tablet container, which is placed in position while the remaining half of the card is folded over to the back. It is the flange portion of the blister that is required to secure the bottle. The flange is “trapped” between the front and back of the card. A heat activated glue secures the flange on the blister to the paperboard card.

Blister Sealing MachineIn some cases, an application to trap a blister will require that the flange not be directly adhered to the paperboard. This version aids in recycling efforts. To achieve this, the flange of the blister is widened thus providing more surface area for the blister between the paperboard cards, and consequently, this improves the security of the overall package. The paperboard is still sealed with heat activated adhesives, but these adhesives do not come into contact with the plastic blister thus allowing the paperboard and blister to both be easily recycled.

In either method, the result is a very secure, tamper evident blister package. The volume of blister packages often warrants the use of sealing equipment, as shown to the right. A blister can be designed for any size or shape item, blisters are great for hanging or stacking in retail environments and blisters reduce loss.

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