There are several companies that can provide premade header bags, but not many that build header bag making equipment.

Header bags are made in various designs; the common feature is that they have a section that is made of a breathable material. This breathable porous section provides for sterilization of the contents with ethylene oxide gas (EtO). Invariably, the physical nature of the material used in the porous section is different than that of the clear plastic film used for the basic bag. The web of composite material used to make header bags can be difficult to control as it passes through the manufacturing process. A Canadian machine builder, GN Packaging, may be able to build a machine that will suit your needs. A list of premade bag suppliers can be found in the PMP News Buyers Guide.

There is a substantial amount of current information about blister packaging available from trade journals. New materials and technology are constantly emerging.  One must be vigilant and seek out the latest information that applies to specific applications.  FDA’s Center for Drug Evaluation and Research offers guidance with the CDER Data Standards Manual. The Wiley Encyclopedia of Packaging Technology is also a reliable source.

There are many different formulations of medical papers and the specifics of achieving certain results depends upon the characteristics of the selected medical packaging paper, the coating that is applied, and the additives that may be included within the PE film being applied. Medical packaging also includes sheet materials that are proprietary polymeric formulations such as Ovantex from Oliver/Tolas and Tyvek from DuPont. A comprehensive treatise on the subject of material selection was published in the February 2001 issue of PMP News.

A well-executed sealing procedure is required to achieve absolutely consistent results.  The seal must be smooth, clean, and predictable. The specifications for a precision seal cannot be established until the material combinations are known. The sealing parameters can be developed in cooperation with the material suppliers and the heat sealer manufacturer. It is, however, absolutely essential to use precision sealing equipment to achieve a consistent precision seal. The time and temperature of the heating cycle as well as the dwell time of the cooling cycle must be maintained within narrow windows of opportunity. A free booklet on sealing systems that employ Toss Technology for high precision is available at www.tossheatseal.com.

As far as determining burst strength goes, the question of establishing a reasonable standard for burst strength is very pragmatic. One needs to consider the forces that may be applied to a package from its formation until it arrives at its point of use.  The mode of subsequent handling and environmental influences must be considered. Will it be shipped by air?  If so, will it be in a pressure-compensated compartment? The safest solution is to use information collected from similar packages or create samples for testing. The greater question is, “How can burst strength be improved?”

Package configuration can improve burst strength. Longer, slender packages are stronger. In addition, the use of impulse seals with tapered heat-seal bands improves seal strength and eliminates the risk of “zipper” failures along the edge of the seal.

The Nylon film that is being used in this application is likely a coextruded material with a sealant layer on one side that is probably polyethylene (PE). The sealant layer on the Nylon is essential because the sealing temperature of both the Tyvek and the PE sealant layer are about 120 °C, whereas the sealing temperature of Nylon is 220 °C. Because the sealing temperature of the sealant layer is close to that of the Tyvek, the bond can be accomplished without overheating the Tyvek.

The ideal sealing temperatures of these materials vary somewhat depending upon their actual composition.  It is always good to request recommended sealing parameters from the film supplier.

The seal strength target seems very high (2.5 lb). A target close to 1 lb for bonding these materials would be more conventional.

High-quality sealing is best accomplished with the ability to control sealing time, sealing temperature, cooling time, and, of course, pressure. When using a rotary sealer one needs to be able to control the temperature and the speed and ideally incorporate a cooling section before the work piece is released. In addition, when sealing Tyvek to a Nylon coextrusion, it is best to apply the heat from only the Nylon side. The rotary band sealer temperature should be high enough to drive the heat through the Nylon and yet not exceed the ideal sealing temperature of Tyvek.

The ability of a sealer to be universal in it its ability to seal different materials depends upon the range of the time, temperature, and pressure adjustments that are available on the machine.  In addition, consistently repeatable seals can only be made if the machine has precise temperature controls that automatically adjust to the gradual heat build up in the machine during the course of the day. For seals to be uniform over their full length, it is imperative that the heat and pressure distribution be uniform over the full length of the seal bar.

Tyvek/PE pouches are best sealed by applying heat from only the PE side. The sealing of foil laminates requires additional heat energy during the sealing process because the foil layer is an excellent thermal conductor that will conduct heat away form the seal area very readily. In this case the sealing is best achieved by providing heat from both sides. The additional heat delivered will accelerate the sealing process and compensate for the heat absorbed by the foil. Some impulse sealing machines are designed to provide the option of heating  from either one or both sides.

The answer depends upon the capabilities of the bar sealer that is currently being used. There are several parameters that must be controlled to ensure an optimum heat seal; temperature and pressure during the heating cycle, duration of the heating cycle, duration of the cooling cycle, or the temperature extent before the release of pressure. If these parameters can be controlled, the sealer can produce excellent seals on virtually any combination of sealable materials.

Coated Tyvek allows for a wider range of sealing parameters.  When using uncoated material the time/temperature cycle must more closely controlled to ensure an acceptable peelable seal.  Not all sealing machines are designed to ensure consistently repeatable control. When a Tyvek pouch is peeled open, the surface layer of the Tyvek delaminates if the seal has been properly made.  If the seal has been overheated or over-pressured while sealing, the seal will become brittle and opaque, and the Tyvek layers will not separate properly.

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