Modern industry is based on polymers as indispensable materials. They form an infrastructure that sustains megacities and advanced technologies that fuel the digital era. The plastic materials may seem durable but may not be safe from microbial attack. ISO 846 is an antimicrobial plastic testing standard that specifies the requirements for testing the resistance of plastics to microbial agents.
ISO 846 ensures that the manufacturers of the polymers are indeed capable of protecting their products against microbial degradation, which enhances longevity and performance in challenging environments. But what is included in ISO 846 and why would this be important to industries in the modern world?
What is ISO 846?
ISO 846 defines the test methods to determine the resistance of plastics to microorganisms. This International Standard specifies a method for determining the degree to which plastic materials resist the attacking action exerted by fungi, bacteria and soil microorganisms on the material when exposed to them. This International Standard does not apply to the determination of the biodegradability of plastics. The aim is to provide information about the resistance of plastics against biological attack, which may influence their mechanical and physical properties.
Scope of Application
ISO 846 antimicrobial plastic testing is applicable to all types of plastics, including those used in various industries, such as:
- Construction: The plastics used in building materials and infrastructure.
- Medical Devices: Polymers in healthcare settings that need to resist microbial contamination.
- Consumer Goods: Plastics used in everyday items like packaging, furniture and household products.
- Automotive and Electronics: Components that require long-term durability against microbial exposure.
The standard helps the manufacturer develop plastics that can resist microbial-induced deterioration, which thereby helps in product longevity and product safety for different applications.
Why is ISO 846 Important?
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. That will surely help them manufacture 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.
Regulatory Compliance
In areas such as health and construction, regulatory bodies often demand plastics to exhibit resistance to microbial growth. ISO 846 for antimicrobial plastic testing assesses compliance with these regulations, helping manufacturers avoid legal issues and possible recalls of their products.
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 the material under investigation and allows the estimation of the resistance of materials against microbial attack.
1. Resistance to Fungi (Method A)
This antimicrobial plastic testing method covers the determination of the inherent resistance of plastics to fungal attack. Plastic samples are exposed to selected fungal strains under suitable conditions for growth. The microbial growth can occur only if the plastic is providing a nutrient source, preventing plastic deterioration. The rate of fungal growth is assessed and marked on a 0 to 5 scale, where 0 indicates no growth and 5 indicates heavy growth.
2. Determination of Fungistatic Effect (Method B)
In this method, plastic samples are placed on a nutritive medium that promotes fungal growth. The fungistatic effect is evaluated by determining the absence of fungal growth on the surface of the plastic. The retarded growth means the resistance of the plastic to colonization with fungi.
3. Resistance to Bacteria (Method C)
This method assesses the resistance of plastics to bacterial attack. Antimicrobial plastic testing specimens are subjected to bacterial suspension under controlled conditions. At the end of incubation, the specimens are examined for evidence of bacterial growth and changes in physical properties.
4. Soil-Burial Test (Method D)
Samples are buried in soil and incubated under controlled conditions of temperature and humidity. This method is performed to determine the resistance of plastics to microorganisms in soil. After a defined period, the samples are evaluated for physical deterioration resulting from microbial attack in the soil.
Test Conditions and Requirements
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. Longer exposure times may be necessary for materials that are expected to remain in contact with microorganisms for extended periods, such as plastics used in construction or buried underground.
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.
How is the ISO 846 Test Conducted?
1. Preparation of Test Specimens
The plastic samples are prepared in accordance with the recommendations given in the standard, that would represent the intended application of the material. The samples are cleaned, sterilized and conditioned before testing to remove contaminants that might interfere with the test results.
2. Inoculation and Incubation
According to the selected method of antimicrobial plastic testing, specimens are inoculated with microorganisms in suspension. Specimens are incubated under fixed conditions of temperature and humidity for the defined period.
3. Evaluation of Results
After the incubation period, the samples are then evaluated for any change in physical properties like mass, appearance and tensile strength. Visual examination is extended by using the microscope, if necessary, to determine the extent of microbial growth on the samples.
4. Calculation of Microbial Resistance
The amount of physical deterioration and microbial growth on the test sample is measured against the microbial growth of the control samples. A material passing the test would present minimal changes and microbial growth.
Role of Testing Laboratories
ISO 846 antimicrobial plastic testing is done with involvement of accredited microbiological laboratories. These laboratories follow specific protocols to deliver complete assurance of the accuracy and reliability of the tests. In this way, the testing labs support the manufacturers to ensure their products meet the required standards related to microbial resistance.
ISO 846 is one of the most important standards that enable the manufacture of plastics resistant to microbial degradation. Manufacturers that adhere to the testing methods in this standard will ensure that their products are durable, safe and comply with industry regulations. From healthcare to construction and consumer goods, plastics meeting ISO 846 standards are more resistant to microbial attack, performing for longer periods under extreme environments.
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.
