3-A Requirements for Rubber Materials
This paper describes the general requirements for multiple-use rubber and rubber-like materials in 3-A Sanitary Standards. Readers should obtain a copy of the complete current standard for details or consult with a qualified laboratory authority on the testing protocol. To obtain this standard, go the 3-A SSI web site home page, click on ’Purchase 3-A Sanitary Standards and 3-A Accepted Practices’ and follow to purchase information for 3-A Sanitary Standard #18- , 3-A Sanitary Standards for Multiple-Use Rubber and Rubber-Like Materials Used as Product Contact Surfaces in Dairy Equipment.
What does this standard cover?
This standard pertains to the material and serviceability requirements of rubber and rubber-like materials used as product contact surfaces. The primary uses of these materials in typical dairy and food processing operations are for liquid product hoses, food conveyor belts, and gaskets for pipelines and equipment.
This standard specifically excludes hard rubber and provides a definition for the composition of these materials. In addition, the standard specifically excludes room-temperature-vulcanized (RTV) silicone adhesives or sealants. They are considered suitable only for certain nonproduct contact sealing applications.
Why a 3-A Sanitary Standard for rubber materials? Isn’t FDA food grade testing sufficient?
Compliance with FDA regulations in CFR Title 21, Part 177.2600 is a primary requisite of the 3-A Standard. FDA specifies the permitted "ingredients" for food grade rubbers, that is, the natural and/or synthetic polymers and the adjuvant substances (e.g. vulcanization materials, antioxidants, plasticizers, fillers, colorants, etc.). The 3-A Sanitary Standard specifies additional performance requirements to establish acceptance for these applications. Specifically, the materials must meet requirements for compatibility with cleaning and sanitizing agents under accelerated use-simulating conditions. These tests are intended to evaluate the rubber physical properties and to assess performance of the rubber under accelerated simulated dairy product contact and cleaning conditions. The specified laboratory testing concerns milk fat absorption, air aging stability, and tests for compatibility with cleaning and sanitizing agents.
Is there one best or "ideal" formulation of rubber for dairy and food uses?
No, the wide variety and composition of dairy and food products, together with the diverse requirements of the processing equipment, necessitate a wide range of rubber formulations.
The standard does establish four classes of rubber mainly delineated by the expected temperature of exposure to product or sterilization. For instance a Class III rubber is considered suitable for exposure to product up to 120°F (49°C), and temperature of exposure to chemical solution used in cleaning and bactericidal treatment up to 180°F (82°C). Although meeting the 3-A Sanitary Standard, such a Class III rubber would not be considered suitable for a Class I use involving exposure to temperatures up to 300°F (149°C).
Is a rubber material that meets all four classes suitable for the manufacture of any equipment covered by a 3-A standard?
Technically, yes, but it wouldn't be a good idea. For satisfactory service, rubber material should be compounded to meet the performance criteria for its intended use. The 3-A Sanitary Standard covers only some of the sanitary aspects. Tests for other performance properties that may be desirable for a given application may be measured by established ASTM tests.
Once a rubber formulation or compound is tested and found to conform to the requirements of a given class(es), How often is subsequent testing required?
Re-testing of the compound is required only if the formulation is changed, at which time, the compound number should also be changed.
Is there any color preference for dairy rubber materials?
No. The color of rubber materials will vary depending on the ingredients and formulation, but the color of the final product has no sanitary significance. If colorants are used, they must conform to the FDA food color additive regulations.
Is there a list of sources of rubber compounds that meet the 3-A Sanitary Standard?
To our knowledge, there is no such list. Previously, 3-A SSI maintained such a list for plastics, but discontinued the list. It was not possible for the limited staff to keep the list current.
Who should do the required laboratory testing—the rubber manufacturer, the rubber parts manufacturer, or the user?
The standard does not address this matter, but only the rubber manufacturer can attest to compliance with the basic FDA requirements. In fact, the Appendix of the standard includes Example of a Rubber Certification Form, which shows combined wording that certifies compliance with both FDA and 3-A test requirements. However, this would not rule out situations where the rubber parts manufacturer or user could 1) obtain a FDA compliance certification from the rubber manufacturer, 2) perform or underwrite the required 3-A laboratory testing, and 3) prepare the standard’s sample or similar certification form. In the latter case of course, the certifier should have an understanding with the rubber manufacturer requiring notification of any changes in the formulation.
How can I find a list of companies that make “food grade” rubber?
You may consult the industry trade association, the Rubber Manufacturers Association. The RMA web site has a directory of RMA members at www.rma.org, but it does not break out the “food grade” rubber manufacturers.
Is there a list of laboratories that specialize in testing rubbers or that are capable of performing the required 3-A tests?
To locate such a laboratory, try the following sources:
ASTM International at www.astm.org.
American Council of Independent Laboratories at www.acil.org.
American Association for Laboratory Accreditation at www.a2la.org.
Is it a big job to run these 3-A rubber tests?
Performing these tests successfully does require specialized laboratory equipment and knowledge of proper laboratory procedures. Five ASTM Standards are referenced and the rubber samples must be prepared and tested according to carefully prescribed procedures.