By Dr. Robert Rotzoll and Christian Geubert, Freudenberg Sealing Technologies
Food production and processing requires a high degree of cleanliness and hygiene in industrial operations. The materials used in food processing equipment must be impervious to ingredient and flavor-absorption and prevent leaks and other malfunctions that could expose the product to contamination.
Standards regulating which material ingredients are approved for food and beverage applications have been established throughout the world. These “positive lists” — lists of approved ingredients for food contact materials — can differ from country to country, however, and can limit the ability of food and beverage producers to use universal seals in the equipment they are using in different regions. This complicates equipment production and procurement and also introduces new cost and quality concerns across the industry.
In response to this challenge, Freudenberg Sealing Technologies has tested new EPDM (ethylene propylene diene rubber) materials, as well as other proven elastomer materials, for global use in the food and beverage industry.
The GB 4806 and GB 9685 standards that have been enforced in China for food and beverage applications since 2016 deviate considerably from relevant U.S. and EU regulations. In particular, the ingredients that may be contained in a seal in contact with a product, as listed in the GB 9685 standard, differ significantly. The list of chemical ingredients permitted for use in China — the positive list — does not include many chemicals that are compliant with FDA (Food and Drug Administration) and EU regulation 1935/2004 for elastomers.
For example, the positive list for China does not list the wide choice of crosslinking chemicals and antioxidants the material developer is used to choosing from when targeting U. S. and European markets. This exclusion reduces options for developing global material recipes.
Although it is possible to get a chemical ingredient added to the positive list, the requirements to do so are onerous. The immense effort that toxicological testing of each raw material would require represents a major hurdle that is not readily overcome by elastomer manufacturers alone. Therefore, for global food applications, new and existing compounds must be developed and tested for conformity using chemical ingredients allowed in China.
Challenge for material developers
EPDM offers outstanding resistance to hot water, steam, acids and bases, and accounts for 70% of all food production and processing material applications currently in use. To provide customers with EPDM materials that meet global food standards, material chemists at Freudenberg first compared the individual chemical ingredients of proven U.S. and EU-compliant materials with the Chinese positive list. The chemists identified several chemicals in use in the U.S. and Europe that had not been tested and approved in China.
Using the existing EPDM formula as a baseline, the chemists developed an alternate formula that included only chemical ingredients approved for use in China, the U.S, and the EU. Material characteristics like resistance to aggressive media, as well as material longevity in a variety of operating environments were important to the development of a global material solution. The outcome of this development is new compounds that are, indeed, compliant for food and beverage use throughout the world.
New EPDM high-performance materials with global approval
The three new material compounds, 70 EPDM 382, 75 EPDM 386, and 85 EPDM 387 offer, high resistance to aging and media that are comparable to the proven food-compatible elastomers.
70 EPDM 382 is specifically optimized for injection molding of uniquely engineered components developed upon request. 75 EPDM 386 and 85 EPDM 387 are suited for use in as O-rings or other standard machined seals and accommodate the need to quickly produce sample parts or small-series runs for customers to help them avoid costly downtime.
The portfolio of materials also includes two existing diaphragm materials, 60 EPDM 217952 and 70 EPDM 217937, that were found to be compliant with Chinese standards with no ingredient changes required.
All five of these material options have been tested and successfully meet sensory and migration requirements for food contact in China, the U.S., and Europe. Also, all of these premium elastomers meet the stringent requirements of the food industry when evaluating resistance to aggressive processes and cleaning media.
Conformity of proven VMQ silicone rubbers
Despite its versatility, EPDM is not the optimal material for all food applications. Foods that contain fat, such as dairy products, must be processed in equipment that uses fat-resistant seals.
Again, to offer globally compliant seals for these applications, the Freudenberg team tested two existing materials against Chinese food safety standards. The two VMQ silicone rubbers, 70 VMQ 117055, and 60 VMQ 117117, have been successfully used in numerous customer applications for years and meet requirements in every respect.
In addition, the materials demonstrate a significantly low level of migration, with a result of < 1 mg/dm2 for both silicones, which is far below the specified limit of ≤ 10 mg/dm2 in the migration measurement. They also have good resistance to CIP/SIP media and can be used in a high-temperature range.
Behavior in aggressive cleaning media and water vapor
In addition to the tests required to verify conformity with U.S., EU, and Chinese standards, additional application-related tests are performed in Freudenberg laboratories. These tests are designed to ensure that the respective materials meet the requirements of the food industry concerning resistance to process and cleaning media.
Cleaning media based on acids, bases, and peroxides sometimes present a greater challenge for sealing materials than the product medium itself. For storage tests, the test specimens are exposed to various media over one to four weeks and then examined for their properties.
In comparing the existing U.S.- and EU-compliant 70 EPDM 291 with the two new globally-compliant materials 75 EPDM 386 and 85 EPDM 387, only moderate changes in mass and volume — as well as minor changes in the mechanical characteristics elongation, modulus, and tensile strength — are observed when exposed to basic and acidic cleaning media. (See figure 1)
The same results are obtained under the influence of steam at 160 °C and the results of the globally compliant materials 75 EPDM 386 and 85 EPDM 387 are comparable to U.S.- and EU-compliant 70 EPDM 291 at 180 °C. (See figure 2) This difference of 20 °C, against the backdrop of the limited selection of ingredients, is a very good result.
When comparing the new materials, tested at 160°C, to a competitor’s China-compliant material tested at only 140°C, the results are even more impressive. Despite the competitive materials exposure to a 20 °C lower temperature, the new compounds outperformed the competitive material with smaller changes in key performance measures. (See figure 3).
Broad portfolio and customized seals
The sealing materials tested provide the market with materials for worldwide use in the food industry. They comply with the relevant standards and have often proven long service life and good media resistance. Both EPDM and VMQ materials are available as O-rings, diaphragms, and customer-specific parts. EPDM materials are also suited for the lathe-cut manufacturing of products.
Freudenberg Sealing Technologies