Medical Device Link.

NEWS

WholeSeal can be applied to Tyvek and paper to facilitate pressure-decay testing.

Medical device packaging consultant and inventor Donald Barcan has developed a material intended to enhance porous-package testing. WholeSeal is an aqueous polyurethane emulsion that can be applied to the exterior of the porous side of the package. Barcan reports that this coating is effective when applied to a spun-bonded polyolefin or paper. WholeSeal is available from Donbar Industries Inc. (DBI Inc.; Long Valley, NJ).

Applied by brush or roller, WholeSeal air-dries to an impervious thin film. (Drying can be sped up by using an air dryer or low-temperature oven.) Upon drying, the film, which is also flexible and continuous, turns that porous package into a nonporous one, enabling users to test for seal integrity or for integrity defects such as pinholes in the uncoated side of the package. WholeSeal is not removable.

Barcan reports that current porous-package testing for either seal integrity or package integrity usually involves using dye testing or underwater bubble testing, or some variation of these tests. “These tests are messy and are limited as to the size of defect that can be detected, and also rely on good operator technique,” he says. “One major problem with these tests is that the results are qualitative, not quantitative. There are other test methods for package and seal integrity, as described in ASTM F2228 and F2338. But these tests require expensive test equipment and use a removable mask, like tape, to eliminate the porosity of the permeable side of the package.”

Once dry, the coated package can be tested for leaks using current pressure-decay technology such as that described in ASTM F2095. Barcan says that the process has been tested and shown to detect imperfections below 25 µm in size, but is limited to the sensitivity of the test equipment. Specifications can be written around a specific quantitative leak rate, and exceeding that could be considered a package failure. This coating will also extend the time available to do dye testing because the dye will not penetrate the coated side as quickly as the uncoated porous material.

Material Shown: Tyvek2FS, WholeSeal Coated (arrow or line shows contact area) Magnification: 246×

WholeSeal can be used to test packages created on form-fill-seal packaging machines where the formed side of the package is a flexible film. “There is always an opportunity for significant cost reduction by either changing the film construction or gauge and changing the forming plug or tool,” Barcan says. “Using WholeSeal and ASTM F2095, the user will be able to quantitatively measure whether the changes are acceptable or not.”

Barcan says that during ASTM committee meetings there has been discussion concerning modifying ASTM F2095 to include the application of a film-forming coating to the permeable side of the package in order to facilitate pressure-decay testing. One of the major concerns was whether the coating penetrates through the permeable material. “If it did, one could assume that the coating could fill any seal imperfections, such as channels, and thereby invalidate the results of the pressure-decay testing for seal integrity. This phenomenon could be called ‘wicking through the material’,” says Barcan.

“Coatings, in general, are not designed to prevent wicking through the permeable materials,” he adds. “WholeSeal is a film-forming coating that is designed to prevent complete wicking through most medical packaging materials.”

To verify that this is true, Jan Gates, principal packaging engineer at Abbott Vascular, arranged for scanning electron microscope (SEM) photos be taken of typical medical device porous materials that were paint coated from a foam brush with WholeSeal. Several materials were evaluated, including Ovantex, 50# latex reinforced paper, Tyvek 2FS, 30# MG paper, Tyvek 1073B, Tyvek 1059B, 42# surgical paper, and coated Tyvek 1073B. Two SEM images are shown on page 14.

When the ASTM F2095 standard is modified, it will become the responsibility of the test user to ensure the coating does not penetrate the material under test, says Barcan. “This could involve SEM or any other method that gives the test user verifiable evidence that the coating does not wick through the material. Independently satisfying this requirement is key to using a film former, such as WholeSeal, to test for seal integrity. On the other hand, for evaluating pinholes in flexible formed materials, the only requirement should be ensuring the uniform and complete application of the porous web to ensure that web is no longer porous to the sensitivity that the test requires.”

WholeSeal could also be used to satisfy ASTM 1140 and F2054. Where the porous side of the package becomes too large given a particular surface area for the internal pressurization to overcome the loss through the permeable material, WholeSeal can seal off porosity to enable accurate and repeatable burst test data. The issues of accuracy and repeatability have not been determined at this time.

ASTM is working on modifications to these test methods to allow the use of materials like WholeSeal.

Pressure-decay testing was conducted using an MDT-500 unit on loan from Steve Franks of T.M. Electronics (Boylston, MA).