Overview
EN ISO 846:2019 (ISO 846:2019) - Plastics - Evaluation of the action of microorganisms - specifies standardized laboratory methods to determine the deterioration of plastics caused by fungi, bacteria and soil microorganisms. The standard is intended to assess microbial deterioration (biodeterioration) - not to measure biodegradability or the breakdown of natural-fibre composites. Tests apply to plastics with even, cleanable surfaces (porous materials such as foams are excluded).
Key topics and technical requirements
- Test methods: Four principal procedures are defined:
- Method A – Fungal‑growth test (visual assessment of fungal colonization).
- Method B – (Note: Test B from earlier editions has been deleted in this edition.)
- Method C – Resistance to bacteria.
- Method D – Soil‑burial (resistance to microbially active soil).
- Assessment metrics:
- Visual examination of surface growth and damage.
- Change in mass of specimens.
- Changes in other physical properties (mechanical, optical, etc.) as specified by the user.
- Specimen requirements:
- Standardized specimen size defined (50 mm × 50 mm) to allow consistent evaluation and to check edge effects (area within 5 mm from the edge).
- Tests require even-surfaced, cleanable plastics; porous foams are excluded.
- Controls and reproducibility:
- Introduction of stainless‑steel negative control coupons to indicate background fungal growth in test containers.
- Positive control specimens are included to assess baseline fungistatic effects.
- A grid is provided (Annex C) to quantify area of fungal surface growth for objective visual scoring.
- Test environment:
- Fungal tests use the same test fungi as IEC 60068-2-10; the IEC approach (assembled specimens inoculated with a spore suspension, incubation and assessment) is referenced.
- Incubation humidity is achieved using a water reservoir in closed containers (target ~95% RH) rather than agar as a moisture source.
Applications and users
Who benefits from EN ISO 846:2019:
- Plastics manufacturers and compounders assessing material resistance to microbial attack.
- Quality control and testing laboratories performing standardized acceptance or routine tests.
- Product designers and specifiers selecting materials for applications exposed to high humidity, soil contact or microbial environments.
- R&D teams evaluating additives (antimicrobials, fungistats) and formulations for improved microbial resistance.
Practical uses include material selection, failure investigation, claims substantiation and comparative screening of formulations.
Related standards
- IEC 60068-2-10 (test fungi and assembled‑specimen fungal‑growth approach) - referenced for fungal strains and inoculation technique.
- The standard supersedes EN ISO 846:1997; consult normative references and annexes (A–D) in EN ISO 846:2019 for test details, soil water‑holding determinations and strain information.
Keywords: EN ISO 846:2019, ISO 846, plastics testing, fungal resistance test, soil‑burial test, fungistatic assessment, microbial deterioration of plastics.