Induction sealing is a low-cost approach that can deliver secure, hermetic and easy opening seals that are ideally suited to pharmaceutical and nutraceutical products for this growing market.
Back in 2002, the UN already had cause to note the remarkable ageing of the global population, regarding it as “unprecedented and without parallel in human history.” Nearly two decades later, that trend has largely continued. Lifespans, particularly in Organisation for Economic Co-operation and Development (OECD) developed nations, are generally getting longer.
To no small degree, this trend has been enabled by the development of pharmaceuticals, nutraceuticals and over-the-counter (OTC) medicines — all products that are delivered to the consumer in securely sealed, tamper-proof packaging.
For most manufacturers, producing secure packaging that also provides a hermetic seal to protect the contents has been the primary goal to date. However, in the context of an ageing population with less dexterity and strength or physical conditions such as arthritis, such packaging can in fact represent a significant challenge for consumers.
Achieving tamper-evident and hermetic sealing that is also easy to open has presented manufacturers with a number of notionally incompatible objectives. For some time, the packaging industry has seemingly been struggling to meet all three requirements simultaneously.
Ensuring product security
For pharmaceuticals and similar products, tamper-evident packaging is a widespread regulatory requirement. The US Food and Drug Administration (FDA) was among the first to issue regulatory ordnance for tamper-evident packaging following the malicious tampering of a pharmaceutical product. The so-called “Chicago Tylenol murders” in 1982, involving cyanide contamination of the paracetamol brand, prompted the introduction.
Those regulations require one or more barriers that provide a visual indication of packaging integrity, together with appropriate labelling that will allow the consumer to confirm, prior to use, that the packaging has not been compromised.
In addition, to reduce the chance of tamper-indicators being fraudulently reinstated after breach, they should carry characteristic identifying marks such as a pattern, logo or product name. Following FDA’s lead, other major regulatory authorities around the world have since incorporated similar requirements for tamper-evident packaging into their own regimes and best-practice manufacturing guidelines.
Beyond regulatory requirements and the need to prevent malicious tampering, manufacturers and retailers also value tamper-evident packaging as an aid to the prevention of theft and counterfeiting in the supply chain. As well as tamper evidence, pharmaceutical containers also need an effective hermetic seal to prevent air and moisture from degrading the product and helping to maintain freshness for longer … as well as preventing product leakage.
With manufacturers, regulators and consumers demanding robust, secure seals that protect the integrity of products and provide clear visual evidence of tampering, a number of different approaches have been adopted to try and achieve these goals.
Pharmaceuticals, OTC drugs such as analgesics, decongestants and antihistamines, and many similar products, are typically sold in plastic or glass containers. Options such as shrink-wrap films, bands or wrappers, boxes with tamper-evident security seals, and breakable caps and tamper-proof peelable seals all are commonly employed as sealing methods on primary and secondary packaging. But consumers also want and need packaging that is easy to use.
A key challenge for many of these technologies is that they can make access to products by legitimate consumers more difficult. Indeed, a potential problem with hermetic sealing on medicine bottles and other similar containers is the very strength of the seal.
Consumers with limited hand strength, dexterity or the necessary hand-eye co-ordination may struggle to “break in” to the product without resorting to tools. That can easily lead to injuries. The difficultly that packaging can present may also affect buying decisions and could cost businesses goodwill. With the ageing population rising in the western world, ease of opening is becoming an increasingly important factor. Properly controlled, induction sealing using the correct lining material can easily achieve all three primary aims of sealing, being both secure, hermetic and easily opened.
Induction sealing
Induction cap sealing is an approach that uses a tamper-evident multilayer laminated liner. Induction liners are a highly engineered layered structure, with each separate layer playing a critical role in the performance and usability of the seal. Comprising an aluminium foil combined with a heat sealing layer that’s tailored to match the container material and product, as well as other layers as required, liners are available in one or two piece designs.
One piece liners are designed for products that do not need to be resealed, whereas two piece liners include a secondary backing board that allows resealing after the tamper-evident seal has been removed.
Using magnetic induction heating, eddy currents cause the aluminium foil layer to heat up and allow a bond to form between the laminate and the container. Before installation, two piece liners are bonded together using a wax coating that disperses when the liner is heated.
Optimum results for induction seals are achieved by making an appropriate choice of lining material and using the correct measure of pressure, heat and time during the induction sealing process. The right heat level, dwell time, cooling period and cap pressure needed for any individual application is highly dependent on the characteristics of the container and its contents.
The initial heating phase may raise the temperature of the liner to 200 ºC or more, but the bonding process between the seal and the closure typically takes place as the joint cools to around 130 °C. Elements such as timing, both heating and cooling, as well as the pressure applied between the cap and the seal, must be carefully controlled to ensure a seal that is both easy to remove and yet still prevents leaks or contamination.
Pressure is needed for the liner to have an even seal to the container rim and this is achieved by the torque applied to the cap when the closure is secured. Insufficient liner pressure or uneven pressure on the land area will result in a poor seal.
A number of technologies are available to offer enhanced security and tamper-evidence in pharmaceutical or OTC applications. Upper layers can be printed for branding or health advisories, or may employ overt or covert anticounterfeit features, such as etched foils, holographic films or colour-changing inks that react when the liner is disturbed.
Significantly, however, properly engineered induction seals are easy to open. The laminated liner can be constructed with grip tabs in various forms and proper control of the sealing process results in a secure bond with the container that nevertheless permits easy removal.
Achieving optimum seals
To achieve full security and usability, particular care is required during the selection of the liner material. Top-tier liner manufacturers are constantly developing products to better match changing consumer requirements. One advance is the emergence of easy-open induction seal designs, such as the Lift ‘n’ Peel TamperSeal from Selig.
Featuring a half moon tab designed to be ergonomic, flexible and extremely strong, it is engineered specifically to maintain product quality whilst being easy for the consumer to peel. In addition, such seals can be printed with a design, logo or instructions.
The complex interactions between the container design and materials, product, liner design, line speed and induction heating variables mean that optimising operating conditions typically requires the advice of expert installers and suppliers to guarantee a reliable tamper-evident seal under production conditions.
Nonetheless, induction sealing does represent an effective and low-cost option for pharmaceutical and nutraceutical product sealing that is secure and tamper-evident, hermetic and easy to open.
With the steady trend of an ageing global population likely to continue, those packaging manufacturers that are evolving to take advantage of a growing market are likely to benefit. Given their success in combining the properties of security, safety and consumer-friendliness, peelable induction seals are set to be a part of this process.
By selecting the most appropriate lining material and optimising the induction heat sealing process, packaging can be easy to open while also being totally secure, ensuring a positive user experience for all consumers. For manufacturers, induction sealing represents a fast, reliable and cost-effective solution to the challenge of accessible tamper-evident packaging.