Why ISO 846 Matters: Testing Plastic Resistance to Fungi and Bacteria

Key Takeaways

• ISO 846 is a qualitative test which evaluates biodeterioration of plastic due to action of bacteria and fungi
• It evaluates damage to plastic materials caused by microorganisms through visual assessment
• The test helps identify risks of surface deterioration, staining, or loss of mechanical strength caused by microbial activity.
• ISO 846 mentions multiple test methods (A–C ) to assess resistance against fungi and bacteria
• It does not evaluate biodegradability of plastic products

Summary

ISO 846 is an international standard used to evaluate biodeterioration of plastic due to action of bacteria and fungi. It helps manufacturers assess material durability by measuring visible growth, mass changes, and physical property degradation. The standard is widely used to validate antimicrobial performance and ensure product reliability in environments prone to microbial attack..

What is ISO 846?

ISO 846 is an international standard that determines how plastics are affected by microorganisms such as fungi, bacteria, and soil microbes. It evaluates deterioration caused by microbial activity rather than biodegradation.

Microorganisms affect plastics in two different ways and ISO 846 is designed to evaluate both.

• Direct action: Microorganisms use components of the plastic as a nutrient source.
• Indirect action: Microbial by-products (acids, pigments, enzymes) alter or damage the plastic.
  

 Why ISO 846 Testing Matters

Plastics in real-world environments are constantly exposed to fungi and bacteria, all of which can affect their appearance, performance, or longevity. Testing product efficacy with ISO 846 helps with a lot of things –

• Product development

In the case of polymer manufacturers, ISO 846 for antimicrobial plastic testing lays down a systematic method to test the resistance of plastics against microbial attacks. Testing helps to ensure that products that can withstand natural environmental exposure and remain durable over time.

• Quality assurance

ISO 846 ensures product quality by setting the criteria on testing and assessment of resistance to microbial attack. Hence, particular criteria set by the standard will allow the manufacturers to understand how resilient their plastics are before bringing them to market.

• Supports product credibility and compliance

ISO 846 testing provides standardized and reliable data to support performance claims.

Scope of Application

ISO 846 applies to solid, non-porous plastics and polymer-based materials commonly used in:

• Consumer and household goods
• Packaging
• Electrical and electronic components
• Construction materials

ISO 846 Test Methods

ISO 846 describes four methods for determining the action of microorganisms on plastics. Each of these methods is designed to simulate the natural environmental conditions relevant to intended application of products  and allows the estimation of the resistance of materials against microbial attack.

1. Fungal growth test ( Method A)

Plastic  samples are placed on a nutrient-deficient medium inoculated  with fungal spores  under conditions of ≥95% relative humidity. After the incubation period, samples are  observed for fungal growth and any changes in material.

2. Determination of Fungistatic Effect (Method B)

In this method, plastic samples are placed  on a complete nutrient medium that promotes fungal growth. The fungistatic effect is evaluated by determining the absence of fungal growth on the surface of the plastic. 

3. Resistance to Bacteria (Method C)

This method assesses the resistance of plastics to bacterial attack. Antimicrobial plastic testing specimens are placed on an incomplete medium which lacks a carbon source. At the end of incubation, the specimens are examined for evidence of bacterial growth and changes in physical properties.

For more details related to ISO 846 test, visit – https://microbe-investigations.com/plastic-testing/plastic-antibacterial/iso-846/

Test Conditions and Requirements testing

ISO 846 standard for antimicrobial plastic testing specifies precise conditions under which the tests should be conducted to ensure consistent and reliable results.

Test Microorganisms

• Fungi: Such as Aspergillus niger and Penicillium funiculosum, which are common in environmental settings.
• Bacteria: Typically, strains like Pseudomonas aeruginosa are used to assess bacterial resistance.

Incubation Temperature and Humidity

24°C to 29°C temperature range is used to incubate the specimens. The relative humidity is at least 90%. These conditions simulate the environments where microbial growth is most likely to occur.

Duration of Exposure

 The exposure time varies depending on the material and the test method but typically lasts for a minimum of 4 weeks.

Passing Criteria

For a plastic material to pass the ISO 846 antimicrobial plastic testing, it must exhibit minimal changes in its physical properties, such as mass or tensile strength, after exposure to microorganisms. The material must also show little to no visible microbial growth on its surface.

What is the difference between ISO 846 vs ASTM G 21

When to choose ISO 846 vs ASTM G21

Use ISO 846 when your product requires:

• Assessment of biodeterioration
• Claims covering both bacteria and fungi as target organisms
• Evaluation of long-term resistance to microbial induced material damage
• Alignment with European and global regulatory expectations

Use ASTM G21 when:

• Evaluating antifungal resistance of plastics and synthetic polymers
• The focus is to understand antifungal performance
• Products are primarily intended for US market requirements 

How MIS can help !

Polymer manufacturers looking to certify your products under ISO 846, Microbe Investigations Switzerland (MIS) can assist you. Contact us today to learn how we can help enhance the durability and safety of your polymer products.

FAQS

1. When is ISO 846 testing required?

 When the product is exposed to moisture, humidity, or environments where microbial growth is likely to happen over time.

2. Is ISO 846 enough to support antimicrobial claims?

No, ISO 846 alone is not sufficient to support antimicrobial claims. ISO 846  is primarily designed for biodeterioration and material resistance against microbial attack, not direct antimicrobial efficacy. For antimicrobial claims, dedicated standards like ISO 22196 or ISO 21702 are typically required.

3. How do ISO 846 results impact product development?

ISO 846 test results help developers understand how a material behaves when exposed to fungi and bacteria, especially in real-world conditions like humidity. Test data helps manufacturers to understand gaps with material selection, additives, and formulations to improve resistance to biodeterioration.

4. What does ISO 846 test measure in plastics?

ISO 846 measures biodeterioration of  plastics  due to microbial attack (bacteria and fungi). It evaluates whether fungi or bacteria can grow on the surface or cause physical damage to material  under controlled test conditions.

5. Is ISO 846 a qualitative or quantitative test?

ISO 846 is a qualitative test. Results are interpreted based on visual assessment of microbial growth and material damage.

6. What is the difference between ISO 846 and ASTM G21?

ISO 846 is used to evaluate potential biodeterioration of plastics against bacteria and fungi  using multiple test methods. ASTM G21 specifically assesses the fungal resistance of synthetic polymeric materials to fungal attack. 

7. Does ISO 846 test biodegradability?

No, ISO 846 does not measure biodegradability. It evaluates microbial resistance and biodeterioration properties of a product.