How direct seal aids medical device packaging

August 21, 2018

7 Min Read
How direct seal aids medical device packaging
Many medical devices use paper packaging, and might be able to improve pack integrity with direct sealing.

Jonathan Andrews

New advances in direct seal systems simplify packaging for medical devices, saving costs, improving printability and enabling optimization of gas sterilization cycles.

By Jonathan Andrews and Matthew Joseph

It’s no secret that U.S. hospitals and clinics have faced tightened budgets in recent years as pressure increases across the board to hold down healthcare costs. An example of these pressures include reduced Medicaid and Medicare reimbursements for hospitals that fail to demonstrate a reduction in healthcare-associated infections (HAIs) in their facilities.

For medical device manufacturers, the new reality of hospital economics has put enormous cost pressures throughout the supply chain, from original equipment manufacturers (OEMs) and their suppliers to hospital purchasing. These pressures have forced manufacturers to scrutinize material choices in packaging. This is particularly the case for large volume Class I and Class II medical devices such as syringes, intravenous (IV) administration kits and urinary catheters.

Because of the large volumes involved, product designers and developers are striving to find cost-savings wherever they can, from enhancements in manufacturing to sourcing more cost-effective materials. At the same time, pack integrity and sterility maintenance remain absolutely essential.

Good insights may be gained by a screening of the technologies used in medical packaging elsewhere in the world. Some packaging systems have many years of history and a proven track record in markets such as Western Europe but have yet to find favor in North America.

Much of the reason for this is an expectation amongst healthcare practitioners that nothing should change. Additionally, that the devices they use will come in packages that look, feel and open just as they have always done. For many devices, there are excellent reasons not to change from the norms. For others, there’s a good opportunity to optimize the pack—and with it packaging costs.

Direct seal

One area to explore is the use of packaging systems that do not require heat seal coatings.  Elimination of heat seal coatings offers a number of benefits such as:

• Coating component cost savings;

• Savings related to no longer requiring additional converting steps;

• Maximizing the porosity of the web, thus enabling optimization of gas sterilization cycles.

Other benefits include minimizing the potential for device/packaging interaction.

The generic name given to systems that seal and peel without heat seal coatings is direct seal. With direct seal systems, the seal is achieved by using heat and pressure to soften the sealing layer of the film until it is forced into the pores of a fibrous porous top web. Direct sealing can be achieved with any fibrous, porous top web, such as a flash-bonded high-density polyethylene (HDPE) or medical kraft paper.


SEM image taken during peeling of a direct seal system. The upper part is the film, with the fibers of the paper clearly visible below. As the pack is peeled apart, the PE forced into the paper by the sealing process stretches. Image courtesy of Amcor Flexibles.


SEM image taken after peeling of a direct seal system. Again the film is uppermost. Fragments of the PE seal layer can be seen left within the paper fiber matrix. It can be seen that the paper surface remains “intact” with this advanced direct seal paper. Image courtesy of Amcor Flexibles.

Traditionally, medical kraft paper direct seal systems have been associated with weak seals and unacceptable levels of fiber tear. Modern, advanced direct seal papers—in combination with specially designed film base webs—have all but eliminated these undesirable characteristics. The use of an on-line treatment on the paper reinforces its surface, preventing fiber tear and allowing much higher seal strengths to be achieved. 


This is an SEM image of the sealed and then peeled area of the film side of a direct seal pack. The imprint of the paper’s fibers can be clearly seen, as can the wisps of the seal layer observed in the earlier images. These wisps turn from clear to grey as they stretch thus giving an excellent “trace,” with resultant confidence to packaging line operators and healthcare professionals that a good seal had been made.


This chart shows part of the heat seal curve from sealing an advanced direct seal paper to a modern direct seal film. It can be seen that the curves remain flat across a range of seal temperatures, indicating a broad heat-seal operating window.

The primary applications for direct seal technology are thermoform-fill-seal packaging processes that have relatively long heat seal durations more than 0.5 seconds). It’s this compatibility that makes direct sealing so well suited to the packaging of three-dimensional devices (see image at top of page).

Enhanced printability

The advent of Unique Device Identification (UDI) has placed much greater emphasis on the printability of packaging materials. This is being driven by a requirement for additional data in both human and machine readable forms. 

Just consider how easy it would be to print both sides of an uncoated, stretch free, receptive material, with fine type. The surface of paper, especially machine glazed (MG) kraft paper, is exceptionally good for printing with its inherent smoothness, which gives excellent fine detail reproduction. Paper’s inherent stiffness minimizes front-to-back registration issues. In addition to these benefits, with no coating on the reverse, a direct seal paper is suitable for double-sided printing as well.


Image at left shows a close-up of a Quick Response (QR) code printed on a medical grade (MG) kraft paper. The code was printed using thermal transfer ribbon of the most common “wax” type. Image at right shows a close-up of a QR code printed on a medical flash-bonded HDPE web. The code was printed using the same wax thermal transfer ribbon as on the previous picture.

In conclusion

As with all medical packaging materials, it is essential to select medical kraft paper suppliers with the requisite competence, experience and certifications. This will ensure medical devices have the appropriate level of protection throughout packaging, sterilization, distribution and use.

Innovative and sustainable paper technologies are helping manufacturers of medical devices navigate cost pressures affecting healthcare, without sacrificing high performance standards. 

Medical kraft papers have an excellent history, are in widespread use throughout the world, and can comply with all the requisite requirements of ISO 11607 Part 1 and relevant sections of the EN868 suite of standards. 


Co-author Jonathan Andrews is business development director, Medical, at BillerudKorsnäs. His background is polymer chemistry and he has been working in the packaging industry since 1986. Following a move into medical and pharmaceutical packaging in 1993, Andrews has held a number of roles including technical sales, technical support, product management and business development. After spending 13 years at Amcor Flexibles, Andrews joined the Speciality Paper group of BillerudKorsnäs in 2014 as global business development director for its SteriKraft and MediKraft Medical Papers. In addition, Jonathan is a member of the ASTM F02 Committee on Flexible Barrier Packaging and a member of the Board of the Sterile Barrier Assn. Reach him at +44 77 699 34 or [email protected].


Co-author Matthew Joseph is sales manager, North & Latin America, Specialty Paper, at BillerudKorsnäs. Joseph has been working in the healthcare packaging industry since 2011, having come from the pharmaceutical industry. After spending four years at Oliver Healthcare Packaging, Joseph joined the Speciality Paper group of BillerudKorsnäs in 2015 as sales manager, North & Latin America. Reach him at 786-427-3387 or [email protected].


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