Digitized stress analysis improves blister performance

Constantia Flexibles’ Live Stress Test analyzes the coldforming process for blister packaging.

Constantia Flexibles (Blythewood, SC), best known for its Coldform foils for blister card packaging, has introduced two services to better analyze the blister card design and manufacturing processes. The Live Stress Check can analyze the performance quality of the packaging process, while a design simulation can point to improvements in the blister card’s overall permeability.

Generally speaking, blister cards provide convenience and therapy-adherence benefits: a blister card can be arranged for, as an example, daily doses per week. The sealed nature of all blister cards improves shelf life of the contained pills as compared to pill bottles; the flat “real estate” of the card allows for messaging and branding to enhance product value. When producing blister packaging with Constantia Coldform, which has an aluminum film layer with near-zero permeability for water and oxygen, the Stress Check can monitor machinery performance.

To perform the stress check, a pattern of high-resolution dots is printed on the Coldform laminate that, when stretched, changes. The Live Stress Check sample, with cavities that were formed under production conditions, is inspected with a camera system and software to determine these distortions. Afterwards, an automatically generated 3D-image (see photo below) illustrates the degree of strain at various areas of the blister—valuable information that allows for significant improvements to both the overall process and the cavity-shaping steps in particular.

A related simulation process addresses another concern: the effect of blister card edges or perforations on “cross permeation”—the intrusion of moisture. Typically, this is addressed by using multilayer films (Constantia can provide films with up to five layers). The company’s simulation technology allows for estimating possible cross-permeation effects, and then the material choices (or placement of perforations and edges) to minimize them. For example, a polypropylene layer could be substituted for more permeation-prone polyvinyl chloride. Carrying out this design process helps ensure overall package quality and speed to market.