ASTM G 21 - Antimicrobial / Antifungal Resistance Test

Standard Practice for Determining Resistance of Synthetic Polymeric Materials to Fungi

The ASTM G 21 testing service determines the effect of fungi on certain properties and characteristics of synthetic polymeric materials. These "materials" may include but are not limited to: paint, plastics, paper, cardboard, dry wall, etc. These materials might be in different physical forms such as tubes, rods, film materials, sheets, etc.

The part of the materials that is synthetic polymer material is usually fungus resistant. This is because the synthetic polymer material itself doesn't provide or act as a source of carbon, which is what promotes the growth of fungi.

Most of the time, what allows the growth of fungus on plastic materials are the other components and constituents of the plastic materials such as lubricants, colorants, etc.

Conditions that are favorable for microbial or fungal production are important to understand when producing these plastic materials. The ASTM G 21 test method determines whether synthetic polymeric materials have established resistance to microbial / fungal invasion under various conditions such as varying temperatures and humidity environments.

Examples of how the ASTM G21 test is applied:

• Assessing the antifungal / antimicrobial activity of paints
• Evaluating the antimicrobial / antifungal activity of plastic materials such as pvc piping, plumbing materials, etc.
• Analyzing fungus, mold, and / or bacterial resistance of construction materials made of or consisting partly of synthetic polymer plastics

ASTM G21 Test Method

ASTM G 21 antimicrobial test method is very commonly used to test the resistance of materials to fungal attacks. High concentration of spore suspensions of each of the five fungi is prepared. Nutrient Salt Agar is poured into sterile petri dishes. Antimicrobial treated Test specimens are placed on the surface of solidified agar. Composite Spore suspension is sprayed onto the surface of agar and test specimens. Inoculated antimicrobial treated test specimens, Antimicrobial untreated Positive controls ( Fungal growth control) and negative control ( Solid agar medium without inoculating mold) controls are incubated at 28 to 30 C for 28 days and under more than 90 % relative humidity.

ASTM G21 Test Sample Requirements

• Three to five pieces of 2 x 2 inch size
• The simplest specimen may be a 50 by 50-mm (2 by 2-in.) piece, a 50-mm (2-in.) diameter piece, or a piece (rod or tubing) at least 76 mm (3 in.) long cut from the material to be tested.

• Film-forming materials such as coatings may be tested in the form of films at least 50 by 25 mm (2 by 1 in.) in size.
• If the specimen is different on two sides, three specimens of each, face up and face down, will be tested upon Sponsor request.

ASTM G21 Turn Around Time

Test itself is 28 days test. Turn around time for ASTM G21 test is 4 to 5 weeks.

Time Lapse / Growth Progression photos can be provided to complement the report results.

Accugen Laboratories, Inc. provides quality testing services of plastic materials using the ASTM G21 test method and other standardized test methods. Call 800-282-7102 for this and other testing services and to receive personalized and customized price quotes.