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ISO 846 Test
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Quick understanding about test
ISO 846: 1997 – Evaluation of the action of microorganisms on plastics
- Aspergillus niger (ATCC 6275)
- Penicillium funiculosum
- Paecilomyces variotii (ATCC 18502)
- Trichoderma virens (ATCC 9645) and more.
- 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
Microbial colonisation on plastic surfaces is influenced by environmental factors such as temperature, humidity and composition of air. Generally, deterioration of plastics by microorganisms occurs in two ways:
- Direct action
In this process, plastics act as a nutrient source and stimulate the growth of microorganisms. Microbial growth over an extended time leads to physical destruction and degradation of plastic material. - Indirect action
This includes metabolic by-products of microorganisms interacting chemically with plastic surfaces to bring about their breakdown.
These microbial attacks can remarkably alter the physical properties and functionality of plastics, leading to deterioration in service life and impairment in their performance. ISO 846 describes a test method to assess this breakdown by exposing non-porous plastic materials to selected microorganisms under conditions specified in guidelines and subsequent measurement of changes in mass, visual appearance and other physical properties.
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. Such information is useful for manufacturers in improving the durability and reliability of plastic products exposed to microbial environments.
Importance of ISO 846 Test
Industries where ISO 846 test is relevant
- Construction industry
These industries rely on this test to assess the performance of plastics in building materials, insulation and structural components, where microbial growth may cause serious damage over time. - Medical Industry:
Plastics used in medical devices, surgical instruments and packaging materials are often exposed to sensitive environments. Testing ensures that these materials do not support microbial growth and reduce contamination risks to the patients. - Agricuture Industry:
Due to the constant contact with soil and high moisture levels, plastics in agricultural machinery, irrigation systems and wrappings are most susceptible to microbial colonisation. Testing plastics using this standard confirms that these materials can withstand such conditions, ensuring durability and reliability in harsh environmental settings. - Consumer goods:
From household containers to everyday plastic items, consumer products should be resistant to microbial growth to maintain hygiene and extend the life of a product. The standard helps manufacturers ensure that their products remain safe for consumers and functional in homes and other environments where microbial exposure is common. - Electrical and electronics industry:
Plastic parts used in electrical devices and appliances are usually exposed to heat and moisture conditions that are most favourable for microbial growth. Testing ensures that these plastics will not lose their insulating properties and structural integrity, preventing potential failures due to microbial deterioration.
Test organisms
At MIS, the ISO 846 test is generally performed using the following strains:
- Bacteria: Pseudomonas aeruginosa (ATCC 15442)
- Fungi: Aspergillus niger (ATCC 6275), Penicillium funiculosum, Paecilomyces variotii (ATCC 18502), Trichoderma virens (ATCC 9645) and Chaetomium globosum (ATCC 6205)
ISO 846 test methods
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)
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.
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.
Benefits of testing
- Regulatory compliance
The standard helps manufacturers meet industry standards and regulatory requirements for plastics to ensure the product meets various global expectations on safety and durability especially in industries such as construction, medical and consumer goods.
- Market advantage
Plastics used in medical devices, surgical instruments and packaging materials are often exposed to sensitive environments. Testing ensures that these materials do not support microbial growth and reduce contamination risks to the patients. - Product development
By identifying potential issues in plastic formulations, testing provides valuable data for improving material composition. This aids manufacturers in making their products stronger and more resistant to degradation via microbial activity. - Consumer trust
Tested products instil confidence in consumers by confirming that the tested products will remain safe, hygienic and functional over time. This is very important for plastics used in medical devices, packaging and food-related applications.
Environmental impact
The standard indirectly helps reduce waste and environmental impact by guaranteeing product durability and microbial resistance, as products do not break down prematurely and end up in landfills.- Brand reputation
Customers perceive companies operating according to ISO standards as a reliable and responsible business partner in both B2B and consumer markets, thus enhancing their brand reputation.
- Regulatory compliance
Guidelines to follow for conducting ISO 846 Test
Specimen preparation
- Ensure plastic test specimens are clean and of the proper size (typically 50 mm x 50 mm) and shape as specified by the particular test method.
- Prepare test specimens in sufficient numbers to meet the requirements for all test methods being conducted (fungal, bacterial, soil-burial).
Selection of microorganisms
- Choose appropriate test organisms based on the environmental exposure of the plastic (e.g., fungi like Aspergillus niger or bacteria like Pseudomonas aeruginosa).
- Testing shall be performed with microorganisms from recognised culture collections, e.g. ATCC or equivalent in order to ensure standardised testing.
Testing conditions
- Maintain controlled environmental conditions during testing, such as temperature (typically 29°C) and relative humidity (≥95%) for fungal growth tests.
- In the case of the soil burial tests, the soil shall possess suitable water holding capacity and moisture content so as to simulate realistic environmental exposure.
Exposure time
- Test specimens should be exposed to microorganisms for a specified period of time, typically determined by the standard and application requirements (often weeks to months).
Visual and physical assessments
- After the exposure period, conduct a visual examination of the specimens to assess microbial growth or discoloration.
- Change in physical properties like mass loss, surface gloss flexural properties and hardness must be measured to determine the amount of deterioration.
Use of controls
- Always include control specimens, such as stainless steel discs, to validate test results by showing the extent of microbial growth in comparison to the plastic material.
- Use positive and negative controls (biocide-treated and untreated specimens) where applicable to determine fungistatic or antibacterial efficacy.
Test documentation
- Thoroughly observe the type of microbial growth, degree of physical changes and any other variations between treated and untreated test pieces.
- Prepare a standard test report in compliance with the requirements of ISO including test methods, microorganisms used, and results obtained.
At Microbe Investigations Switzerland (MIS), we offer comprehensive antimicrobial testing services for products claiming microbial protection, including textiles, disinfectants and coatings. Our advanced microbiology testing facility enables precise evaluation of antimicrobial efficacy, ensuring compliance with international standards.
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 customer’s request.
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