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ISO 846 Test
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Quick understanding about test
ISO 846: 2019 โ Evaluation of the action of microorganisms on plastics
Applicable to a wide range of plastic products that are used in construction, medical, and agricultural industries.
- Aspergillus niger (ATCC 6275)
- Penicillium pinophilum (ATCC 36839)
- Paecilomyces variotii (ATCC 18502)
- Trichoderma virens (ATCC 9645)
- Method A: Fungal-growth test
- Method B: Determination of fungistatic effects
- Method C: Resistance to bacteria
- Method D: Resistance to microbially active soil (soil-burial test)
- Help manufacturers in optimizing plastic formulations.
- Ensures compliance with industry standards .
Results
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Abstract
ISO 846 specifies test conditions and requirements for the measurement of the resistance of plastics to microbial attack, specifically fungi, bacteria, and other soil microorganisms. Plastics are generally highly durable. However, they are not completely immune to avoid microbial degradation. Therefore, evaluating their resistance to microbial attack is crucial to ensure their durability.
The deterioration of plastic materials by microorganisms (bacteria and fungus) is affected by two processes –
- Direct action – Plastics act as a nutrient medium for the growth of microorganisms. This subsequently results in the deterioration of plastic.
- Indirect action – Metabolic products of microorganisms cause the deterioration of plastic.
It’s important to note that this standard does not test the biodegradability of plastics. The standard specifically tests the resistivity of plastics to microbial attack.
Industries where ISO 846 test is relevant
ISO 846 tests are designed for products used in high humidity and soil-rich environments. The industries covered are:
- Construction
- Agriculture
- Healthcare
- Consumer goods
- Electronics
Test organisms
- Bacteria: Pseudomonas aeruginosa (ATCC 15442)
- Fungi: Aspergillus niger (ATCC 6275), Penicillium pinophilum (ATCC 36839), Paecilomyces variotii (ATCC 18502), Trichoderma virens (ATCC 9645) and Chaetomium globosum (ATCC 6205)
ISO 846 test methods
All test methods use a test specimen of the dimensions (50 mm ยฑ 1 mm) ร (50 mm ยฑ 1 mm) to harmonize the growth evaluation. Positive controls, materials which support the growth of fungi are used to ensure fungi and test conditions are viable.
Method A: Fungal-growth test
In this method, plastic test specimens treated with antimicrobial treatments are exposed to a mixed suspension of fungal spores with insufficient nutritive medium (no carbon source) under conditions of โฅ95% relative humidity. The fungi grow only if the plastic acts as a nutrient source. Negative controls, stainless steel coupons, confirm that any growth observed is due to the plastic itself. Suppose the material does not contain nutritive components; the fungal mycelium does not develop, preventing plastic degradation. The test is applicable for comparing the inherent resistance of plastics to attack by fungi in the absence of other organic materials.
Method B: Determination of fungistatic effects
Method C: Resistance to bacteria
In this method, the resistance of plastics to bacterial action is evaluated by placing test specimens on an incomplete medium which lacks a carbon source. If no bacterial growth is observed in the agar surrounding the specimen, it implies that the material does not contain nutritive components to support bacterial growth. This method is typically applied to assess the inherent microbial resistance of plastics.
However, if the material claims added antibacterial or hygienic functionality, it should also be tested according to ISO 22196, which specifically measures the antibacterial performance of non-porous plastics by treating them with biocides.
Method D: Resistance to microbially active soil (soil-burial test)
This test method evaluates plastics which are in contact with soil for long-term periods, such as those used in outdoor applications. Test specimens are buried in microbially active soil of known water-holding capacity and moisture content. The aim is to determine the resistance of the plastic material to microbial attack during an extended period of exposure to high humidity and soil microbiota.
Importance of ISO 846 Test
The ISO 846 test is essential as it:
- Evaluates the long-term performance of plastics when exposed to environments prone to microbial growth.
- Replicates real-world usage conditions to assess microbial resistance of plastic materials.
- Critical test for sectors where plastic degradation can compromise safety, functionality, and service life.
- Test involves both visual inspections and measurements of physical properties to determine material impact.
- Ensures plastics meet durability and performance standards in microbial-rich environments.
Conclusion
At Microbe Investigations Switzerland (MIS), we offer comprehensive antimicrobial testing services for products claiming microbial protection, including plastics, coatings, textiles and disinfectants. Our advanced microbiology testing facility enables precise evaluation of antimicrobial efficacy, ensuring compliance with international standards.
In addition to ISO 846 microbial testing for plastics, MIS performs other testing methods such as ISO 22196, JIS Z 2801, ASTM G21 and ISO 21702 to check the antimicrobial efficacy of treated plastic materials.
For more information on ISO 846 testing or to explore our antimicrobial plastic testing services, contact us today.
Frequently Asked Questions
DR. Martinoz Scholtz
At Microbe Investigations, we perform the test using Pseudomonas aeruginosa (ATCC 15442) and Aspergillus niger (ATCC 16888). Other strains can also be added as per the customerโs request.
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