Article: Preventing premature failure of tamper-evident seals

A tamper-evident seal is often an integral requirement of medical and food packaging, and a premature, incorrect failure of the seal can be costly – both financially and on a brand’s reputation.

There are numerous environmental conditions which can cause the seal to break before arrival – Smithers Pira experts provide an expert commentary on how a comprehensive testing programme can help companies minimise the risk of premature failure.

Distribution

One of the main causes of failure is the damage incurred whilst the product is in bulk transit from manufacturer to its end-use location. The stacking of products and pallets increases the strain placed upon the seal, and friction from other packaging can easily cause seal damage. When combined with the unpredictable motions of manual handling and vehicular movement, weak seals can quickly detach or break apart.

Environmental Conditions

Used widely in medical packaging, the seals also have to endure any intended storage conditions for the drug product contained within. If a drug product has to be refrigerated, then the packaging must also be able to withstand a cooler climate.

Alternatively, if a product is likely to encounter warmer conditions or a pressurised environment then packaging designers need to assess what impact these environments will have on seal performance.

Tamper evident seals should demonstrate adequate resistance to the potentially detrimental effects of temperature and humidity extremes, as well as daylight exposure as appropriate. In particular, elevated temperatures may exacerbate poor resistance to adhesive creep; low temperature a propensity to brittle failure.

The dynamic rupture of a bond demonstrating high bond strength and/or fibre tear gives no indication of the bonds durability to sustained loading. A simple analogy is a self-adhesive label which can be peeled intact if pulled gradually, but tears when pulled quickly. It is therefore necessary to subject bonds to creep resistance tests in order to assure long term durability.

The assessment can be extended to look at the resistance to elevated temperatures associated with some export markets. Low temperature performance of bonds is usually assessed by dynamic rupture in a chilled or freeze temperature chamber.

Long-Term Shelf Life

Companies also need to consider the long-term shelf life of the product (and its packaging). If a medicine is marketed with a five-year shelf life, its packaging – including the seal – must also retain its functionality over the projected lifetime.

Medical device packaging must maintain integrity over its claimed shelf-life under the storage conditions specified by the manufacturer and the same is true of any tamper-evident feature. Smithers Pira can tailor an accelerated aging test programme to your particular requirements.