EtO and Plastic Bags; Shrink-Wrap versus Netting; Is Cyclohexanone Safe for Bonding?

Medical Device & Diagnostic Industry Magazine
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An MD&DI March 1999 Column

HELP DESK

Barry F. J. Page, an industry consultant (Garner, NC), member of the AAMI Sterilization Standards Committee, and cochair of the AAMI Ethylene Oxide Sterilization Residuals Working Group, provides answers to two EtO sterilization queries.

Will EtO penetrate through a plastic bag? If so, what type of plastic can be used, and, if not, does any documentation exist that proves that EtO does not penetrate such materials?

The rate at which EtO penetrates through most plastics depends on the specific material and its thickness. The EtO is actually being absorbed and desorbed from the plastic, and the rate at which this occurs depends on the base materials as well as on any additives, such as plasticizers and extenders, that are included in the formulation.

Some materials such as polytetrafluoroethylene (PTFE), polycarbonate, and nylon absorb low quantities of EtO, but in these types of materials the EtO is tightly bound and difficult to desorb, which makes EtO penetration appear very low. Other plastics, such as polyurethane and polyvinyl chloride (PVC), are both high absorbers and rapid desorbers of EtO. However, because such a large amount of EtO is absorbed and since absorption is generally a faster process than desorption, the penetration rate can still appear deceptively low.

I am not aware of any specific compilation of data that proves that EtO is unable to penetrate specific types of plastic bags. With the variety of base polymers and additive packages available for use, conducting such a study would be quite a daunting task. Vagn Handlos of the Royal Danish School of Pharmacy published some useful data in the late 1970s and early 1980s. If others are aware of similar information, perhaps they could share it with the MD&DI readership.

How significant is the reduction in aeration times using netting versus shrink-wrap when palletizing product for EtO sterilization?

The use of netting rather than shrink-wrap is likely to significantly affect both the EtO sterilization parameters and product aeration times. Depending on the product and its packaging, use of netting is likely to increase the rate of absorption and desorption of EtO. Too many layers of shrink-wrap material can significantly slow both penetration of EtO into the product and aeration of EtO from the product after sterilization. Consequently, netting is probably a better alternative to shrink-wrapping.

Tom Vincent, general manager of Brevet Inc. (Irvine, CA), details various steps to consider when examining the safety of a material for a specific application.

Can cyclohexanone be used as a bonding agent?

Cyclohexanone does an excellent job of bonding PVC materials and is generally considered to be less expensive and easier to use than many other agents. Before using cyclohexanone, however—or any other agent—a manufacturer needs to examine various issues, including, but not limited to, those discussed below.

The manufacturer should call FDA to ask if there is any reason that would prohibit the use of cyclohexanone in the intended application. Will additional testing requirements be imposed because of the introduction of cyclohexanone? Is the grade of the selected cyclohexanone approved for the particular application? One way to check is to search the agency's Web site for published documentation.

Chemical watch lists can also be checked. These are compiled by state specialists who determine which chemicals are known or suspected to present a health hazard. If cyclohexanone appears on such a list, it would be wise to invest in extensive research and legal advice before proceeding with its use. The state agency should provide all necessary documentation to clearly establish its position on the chemical's use. The EPA can provide information on any existing environmental issues at the federal, state, and local levels concerning the use of cyclohexanone.

OSHA officials can advise as to whether working with cyclohexanone poses a health risk and whether the organization has certified or published solutions to minimize such risks. The agency should be contacted early in the project's development.

The cyclohexanone manufacturer can provide copies of its material safety data and product specification sheets. Because there are several grades of cyclohexanone, the grade selected must match the requirements of the specific application. If in doubt, ask the cyclohexanone manufacturer for recommendations on which grade to use and how to apply it. The material safety data and product specification sheets can also help identify potential dangers.

Finally, the supplier of the PVC to be bonded might be able to advise whether using cyclohexanone will affect its material. If the supplier has run tests, it's wise to ask what tests were conducted, what testing labs were used, and whether copies of the test results can be obtained. Most resin suppliers are happy to accommodate such requests.

Although no single one of these sources alone is likely to provide a definitive answer on the use of cyclohexanone for a particular project, the information accumulated from all of them should enable a device manufacturer to make an intelligent, informed decision.

"Help Desk" solicits questions about the design, manufacture, regulation, and sale of medical products and refers them to appropriate experts in the field. A list of topics previously covered can be found in our Help Desk Archives. Send questions to Help Desk, MD&DI, 11444 W. Olympic Blvd., Ste. 900, Los Angeles, CA 90064, fax 310/445-4299, e-mail [email protected]. You can also use our on-line query form.

Although every effort is made to ensure the accuracy of this column, neither the experts nor the editors can guarantee the accuracy of the solutions offered. They also cannot ensure that the proposed answers will work in every situation.

Readers are also encouraged to send comments on the published questions and answers.

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