ASTM G21-15 (2021)e1 PDF

Full title and description

ASTM G21-15(2021)e1 — Standard Practice for Determining Resistance of Synthetic Polymeric Materials to Fungi. This practice describes a laboratory procedure for exposing molded and fabricated polymeric specimens to a defined fungal challenge under controlled temperature and humidity, visually rating fungal growth, and optionally measuring changes in optical, mechanical, or electrical properties after exposure.

Abstract

This standard practice provides a repeatable test method to assess the susceptibility of synthetic polymeric materials (films, sheets, molded articles, coatings, foams, tubes, etc.) to colonization and deterioration by fungi. The test uses a multi-species fungal inoculum, controlled incubation (warm, high-humidity conditions), and a 0–4 visual rating scale to describe the degree of visible fungal growth; microscopic examination and property measurements may be used to confirm or quantify effects. Results assist material selection, product development, and comparative performance claims for fungal resistance.

General information

• Status: Active standard (current edition with editorial update/erratum designated G21-15(2021)e1).
• Publication date: Original designation G21-15 (2015); editorial update/erratum published/recorded in 2021 (designation shown as G21-15(2021)e1; last document update recorded June 22, 2021).
• Publisher: ASTM International (American Society for Testing and Materials).
• ICS / categories: 83.080.01 (Plastics in general).
• Edition / version: G21-15 with 2021 editorial update (G21-15(2021)e1).
• Number of pages: 6 pages (concise practice).

Scope

The practice covers determination of the effect of fungi on synthetic polymeric materials in the form of molded and fabricated articles, tubes, rods, sheets, and film materials. It is intended to establish resistance under conditions favorable to fungal growth; changes in optical, mechanical, and electrical properties can be measured by appropriate ASTM methods. The procedure is a laboratory accelerated challenge and does not attempt to simulate every environmental scenario — conditioning or other pre-treatments that affect resistance are outside the basic practice unless agreed by parties.

Key topics and requirements

• Test organisms: a defined multi-species fungal inoculum typically including Aspergillus (A. brasiliensis / historically A. niger), Penicillium funiculosum, Chaetomium globosum, Trichoderma virens, and Aureobasidium pullulans.
• Incubation conditions: warm, high-humidity incubation — commonly 28–30 °C with relative humidity ≥85% (incubation maintained for the exposure period specified in the practice).
• Exposure duration: specimens are observed during the test and commonly evaluated at 14 and 28 days (many labs report a 28-day exposure as the routine interval; shorter checks at 14–21 days are used for interim assessment).
• Visual rating scale: a 0–4 macroscopic rating system quantifies growth (0 = no growth; 1 = traces, <10%; 2 = light 10–30%; 3 = medium 30–60%; 4 = heavy ≥60% to complete coverage). Microscopy may be used to confirm low-level results.
• Specimen size and replication: typical specimens are ~50 × 50 mm squares, 50 mm diameter discs, or pieces ≥76 mm long; three replicates per material/face are commonly used. Controls (viability/positive control) are included.
• Optional measurements: after exposure, changes in transmission, mechanical properties, mass, dimensions, or electrical properties can be determined using applicable ASTM test methods to quantify deterioration beyond visual growth.

Typical use and users

Used by materials scientists, polymer formulators, product developers, quality laboratories, and test houses to evaluate and compare fungal resistance of plastics, coatings, sealants, elastomers, foams, and related products. Also used by procurement and compliance teams for specification and acceptance testing where fungal resistance is required. Testing is typically performed in microbiology-equipped labs by personnel trained in handling fungi.

Related standards

Related ASTM and international methods and guides referenced for specimen preparation, environmental conditioning, and property measurement (see referenced ASTM methods for optical, mechanical, and electrical testing). The standard has revisions/history tied to earlier G21 editions (reapprovals and past revisions such as G21-09/G21-13/G21-15) and is listed in ASTM’s Book of Standards volume for plastics/microbiological testing.

Keywords

fungal resistance, polymer, plastics, ASTM G21, fungi, mold, antimicrobial, inoculum, incubation, Sabouraud (nutrient-salts) agar, visual rating, accelerated challenge, biodegradation.

FAQ

Q: What is this standard?

A: ASTM G21-15(2021)e1 is a short standardized laboratory practice that describes how to test synthetic polymeric materials for susceptibility to fungal growth and to report visible fungal colonization and consequential changes in material properties.

Q: What does it cover?

A: It covers specimen selection, inoculation with a defined multi-species fungal challenge, controlled incubation at warm/high-humidity conditions, visual scoring of fungal growth (0–4), and optional post-exposure property measurements. It is designed for molded/fabricated polymeric forms and film/coating samples.

Q: Who typically uses it?

A: Polymer formulators, product developers, test laboratories, quality assurance teams, and researchers who need objective, reproducible data on fungal colonization and material deterioration for selection, claims, or regulatory/specification purposes. Testing is normally done by labs with microbiology capability.

Q: Is it current or superseded?

A: The practice is an active ASTM standard identified as G21-15 with a 2021 editorial update (designated G21-15(2021)e1). Users should check ASTM’s official document summary for the latest administrative status and any further amendments.

Q: Is it part of a series?

A: G21 belongs to ASTM’s G03 committee work on biological effects and biodegradation and is related to other microbiological and material durability standards — it has a revision history (earlier G21 editions) and cross-references to ASTM methods for measuring material properties impacted by microbial exposure.

Q: What are the key keywords?

A: Fungi, mold, polymeric materials, fungal resistance, ASTM G21, incubation, visual rating, antimicrobial testing, plastics durability.