ASTM G21-15(2021)e1
(Practice)Standard Practice for Determining Resistance of Synthetic Polymeric Materials to Fungi
Standard Practice for Determining Resistance of Synthetic Polymeric Materials to Fungi
SIGNIFICANCE AND USE
4.1 The synthetic polymer portion of these materials is usually fungus-resistant in that it does not serve as a carbon source for the growth of fungi. It is generally the other components, such as plasticizers, cellulosics, lubricants, stabilizers, and colorants, that are responsible for fungus attack on plastic materials. To assess materials other than plastics, use of this test method should be agreed upon by all parties involved. It is important to establish the resistance to microbial attack under conditions favorable for such attack, namely, a temperature of 2 to 38 °C (35 to 100 °F) and a relative humidity of 60 to 100 %.
4.2 The effects to be expected are as follows:
4.2.1 Surface attack, discoloration, loss of transmission (optical), and
4.2.2 Removal of susceptible plasticizers, modifiers, and lubricants, resulting in increased modulus (stiffness), changes in weight, dimensions, and other physical properties, and deterioration of electrical properties such as insulation resistance, dielectric constant, power factor, and dielectric strength.
4.3 Often the changes in electrical properties are due principally to surface growth and its associated moisture and to pH changes caused by excreted metabolic products. Other effects include preferential growth caused by nonuniform dispersion of plasticizers, lubricants, and other processing additives. Attack on these materials often leaves ionized conducting paths. Pronounced physical changes are observed on products in film form or as coatings, where the ratio of surface to volume is high, and where nutrient materials such as plasticizers and lubricants continue to diffuse to the surface as they are utilized by the organisms.
4.4 Since attack by organisms involves a large element of chance due to local accelerations and inhibitions, the order of reproducibility may be rather low. To ensure that estimates of behavior are not too optimistic, the greatest observed degree of deterioration should be reported...
SCOPE
1.1 This practice covers determination of the effect of fungi on the properties of synthetic polymeric materials in the form of molded and fabricated articles, tubes, rods, sheets, and film materials. Changes in optical, mechanical, and electrical properties may be determined by the applicable ASTM methods.
1.2 The values stated in SI units are to be regarded as the standard. The inch-pound units given in parentheses are for information only.
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.
1.4 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
General Information
Relations
Standards Content (Sample)
This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
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Designation: G21 − 15 (Reapproved 2021)
Standard Practice for
Determining Resistance of Synthetic Polymeric Materials to
Fungi
ThisstandardisissuedunderthefixeddesignationG21;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginal
adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.Asuperscript
epsilon (´) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the U.S. Department of Defense.
ε NOTE—Editorial corrections were made to the footnote in 5.1.1 and to 6.4.1 in June 2021.
1. Scope D495 Test Method for High-Voltage, Low-Current, DryArc
Resistance of Solid Electrical Insulation
1.1 This practice covers determination of the effect of fungi
D618 Practice for Conditioning Plastics for Testing
on the properties of synthetic polymeric materials in the form
D638 Test Method for Tensile Properties of Plastics
of molded and fabricated articles, tubes, rods, sheets, and film
D747 Test Method for Apparent Bending Modulus of Plas-
materials. Changes in optical, mechanical, and electrical prop-
tics by Means of a Cantilever Beam (Withdrawn 2019)
erties may be determined by the applicable ASTM methods.
D785 Test Method for Rockwell Hardness of Plastics and
1.2 The values stated in SI units are to be regarded as the
Electrical Insulating Materials
standard. The inch-pound units given in parentheses are for
D882 Test Method for Tensile Properties of Thin Plastic
information only.
Sheeting
1.3 This standard does not purport to address all of the
D1003 Test Method for Haze and Luminous Transmittance
safety concerns, if any, associated with its use. It is the of Transparent Plastics
responsibility of the user of this standard to establish appro-
D1708 Test Method forTensile Properties of Plastics by Use
priate safety, health, and environmental practices and deter- of Microtensile Specimens
mine the applicability of regulatory limitations prior to use.
E96/E96M Test Methods for Water Vapor Transmission of
1.4 This international standard was developed in accor- Materials
dance with internationally recognized principles on standard-
E308 PracticeforComputingtheColorsofObjectsbyUsing
ization established in the Decision on Principles for the the CIE System
Development of International Standards, Guides and Recom-
2.2 TAPPI Standard:
mendations issued by the World Trade Organization Technical
Test Method T 451-CM-484 Flexural Properties of Paper
Barriers to Trade (TBT) Committee.
2.3 Federal Standards:
FED STD 191 Method 5204 Stiffness of Cloth, Directional;
2. Referenced Documents
Self Weighted Cantilever Method
2.1 ASTM Standards:
FED STD 191 Method 5206 Stiffness of Cloth Drape and
D149 Test Method for Dielectric Breakdown Voltage and
Flex; Cantilever Bending Method
DielectricStrengthofSolidElectricalInsulatingMaterials
at Commercial Power Frequencies
3. Summary of Practice
D150 Test Methods forAC Loss Characteristics and Permit-
3.1 The procedure described in this practice consists of
tivity (Dielectric Constant) of Solid Electrical Insulation
selection of suitable specimens for determination of pertinent
D257 Test Methods for DC Resistance or Conductance of
properties, inoculation of the specimens with suitable
Insulating Materials
organisms, exposure of inoculated specimens under conditions
favorable to growth, examination and rating for visual growth,
This practice is under the jurisdiction ofASTM Committee G03 on Weathering
and Durability and is the direct responsibility of Subcommittee G03.04 on
Biological Deterioration.
Current edition approved May 15, 2021. Published June 2021. Originally The last approved version of this historical standard is referenced on
approved in 1961. Last previous edition approved in 2015 as G21 – 15. DOI: www.astm.org.
10.1520/G0021-15R21E01. Available from TechnicalAssociation of the Pulp and Paper Industry (TAPPI),
For referenced ASTM standards, visit the ASTM website, www.astm.org, or 15 Technology Parkway South, Norcross, GA 30092, http://www.tappi.org.
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Available from Standardization Documents Order Desk, DODSSP, Bldg. 4,
Standards volume information, refer to the standard’s Document Summary page on Section D, 700 Robbins Ave., Philadelphia, PA 19111-5098, http://
the ASTM website. dodssp.daps.dla.mil.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
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G21 − 15 (2021)
and removal of the specimens and observations for testing, 5.1.1 For specimens up to 75 mm (3 in.) in diameter, 100 by
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either before cleaning or after cleaning and reconditioning. 100 mm (4 ⁄4 by 4 ⁄4 in.) plastic boxes or 150-mm (6-in.)
covered Petri dishes, and
NOTE 1—Since the procedure involves handling and working with
5.1.2 For 75 mm (3 in.) and larger specimens, such as
fungi, it is recommended that personnel trained in microbiology perform
tensile and stiffness strips, large Petri dishes, trays of borosili-
the portion of the procedure involving handling of organisms and
inoculated specimens. categlass,orbakingdishesupto400by500mm(16by20in.)
in size, covered with squares of window glass.
4. Significance and Use
5.2 Incubator—Incubating equipment for all test methods
4.1 The synthetic polymer portion of these materials is shall maintain a temperature of 28 to 30 °C (82.4 to 86 °F) and
usually fungus-resistant in that it does not serve as a carbon a relative humidity not less than 85 %.Automatic recording of
source for the growth of fungi. It is generally the other wet and dry-bulb temperature is recommended.
components, such as plasticizers, cellulosics, lubricants,
6. Reagents and Materials
stabilizers, and colorants, that are responsible for fungus attack
6.1 Purity of Reagents—Reagent grade chemicals shall be
on plastic materials.To assess materials other than plastics, use
used in all tests. Unless otherwise indicated, it is intended that
of this test method should be agreed upon by all parties
all reagents shall conform to the specifications of the Commit-
involved. It is important to establish the resistance to microbial
tee onAnalytical Reagents of theAmerican Chemical Society,
attack under conditions favorable for such attack, namely, a
where such specification are available. Other grades may be
temperature of 2 to 38 °C (35 to 100 °F) and a relative
used, provided it is first ascertained that the reagent is of
humidity of 60 to 100 %.
sufficiently high purity to permit its use without lessening the
4.2 The effects to be expected are as follows:
accuracy of the determination.
4.2.1 Surface attack, discoloration, loss of transmission
6.2 Purity of Water—Unless otherwise indicated, references
(optical), and
to water shall be understood to mean distilled water or water of
4.2.2 Removal of susceptible plasticizers, modifiers, and
equal or higher purity.
lubricants, resulting in increased modulus (stiffness), changes
in weight, dimensions, and other physical properties, and 6.3 Nutrient-Salts Agar—Preparethismediumbydissolving
in 1 L of water the designated amounts of the following
deterioration of electrical properties such as insulation
resistance, dielectric constant, power factor, and dielectric reagents:
strength.
Potassium dihydrogen orthophosphate (KH PO ) 0.7 g
2 4
Magnesium sulfate (MgSO ·7H O) 0.7 g
4 2
4.3 Often the changes in electrical properties are due prin-
Ammonium nitrate (NH NO ) 1.0 g
4 3
Sodium chloride (NaCl) 0.005 g
cipally to surface growth and its associated moisture and to pH
Ferrous sulfate (FeSO ·7H O) 0.002 g
4 2
changes caused by excreted metabolic products. Other effects
Zinc sulfate (ZnSO ·7H O) 0.002 g
4 2
include preferential growth caused by nonuniform dispersion
Manganous sulfate (MnSO ·H O) 0.001 g
4 2
Agar 15.0 g
of plasticizers, lubricants, and other processing additives.
Dipotassium monohydrogen orthophosphate (K HPO ) 0.7 g
2 4
Attack on these materials often leaves ionized conducting
6.3.1 Sterilize the test medium by autoclaving at 121 °C
paths. Pronounced physical changes are observed on products
(250 °F) for 20 min.Adjust the pH of the medium so that after
in film form or as coatings, where the ratio of surface to
sterilization the pH is between 6.0 and 6.5.
volume is high, and where nutrient materials such as plasticiz-
6.3.2 Prepare sufficient medium for the required tests.
ers and lubricants continue to diffuse to the surface as they are
6.3.3 Nutrient– Salts Broth—Prepare using the formula in
utilized by the organisms.
6.3,omittingtheagar.Brothmaybefiltersterilizedtoavoidthe
4.4 Since attack by organisms involves a large element of
precipitation of the salts that occurs with autoclaving.
chance due to local accelerations and inhibitions, the order of
6.4 Mixed Fungus Spore Suspension:
reproducibility may be rather low. To ensure that estimates of
behavior are not too optimistic, the greatest observed degree of
NOTE 2—Since a number of other organisms may be of specific interest
deterioration should be reported. for certain final assemblies or components, such other pure cultures of
organisms may be used if agreed upon by the purchaser and the
4.5 Conditioning of the specimens, such as exposure to
manufacturer of the plastic. Reference (1) illustrates such a choice.
leaching, weathering, heat treatment, etc., may have significant
effectsontheresistancetofungi.Determinationoftheseeffects
Available from Tri-State Plastics, Inc., Latonia, KY.
is not covered in this practice. Reagent Chemicals, American Chemical Society Specifications, American
Chemical Society, Washington, DC. For suggestions on the testing of reagents not
listed by the American Chemical Society, see Analar Standards for Laboratory
5. Apparatus
Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia
and National Formulary, U.S. Pharmaceutical Convention, Inc. (USPC), Rockville,
5.1 Glassware—Glass or plastic vessels are suitable for
MD.
holding specimens when laid flat. Depending on the size of the 8
The boldface numbers given in parentheses refer to the list of references at the
specimens, the following are suggested: end of the practice.
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G21 − 15 (2021)
6.4.1 Use the following test fungi in preparing the cultures: along with the test items, with the spore suspension by
A
spraying the suspension from a sterilized atomizer so that the
Fungi ATCC No.
entire surface is moistened with the spore suspension. Incubate
B
Aspergillus brasiliensis 9642
these at 28 to 30 °C (82 to 86 °F) at a relative humidity not less
C
Talaromyces pinophilus 11797
than 85 % and examine them after 14 days’ incubation. There
Chaetomium globosum 6205
D
Trichoderma virens 9645
shall be copious growth on all three of the filter paper control
Aureobasidium pullulans 15233
specimens. Absence of such growth requires repetition of the
test.
A
Available from American Type Culture Collection, 12301 Parklawn Drive,
Rockville, MD 20852.
B
Historically known as A. niger.
8. Test Specimens
C
Historically known as P. pinophilum.
D
8.1 The simplest specimen may be a 50 by 50-mm (2 by
Historically known as Gliocladium virens.
2-in.) piece, a 50-mm (2-in.) diameter piece, or a piece (rod or
6.4.1.1 Maintain cultures of these fungi separately on an
tubing) at least 76 mm (3 in.) long cut from the material to be
appropriate medium such as potato dextrose agar. The stock
tested. Completely fabricated parts or sections cut from fabri-
cultures may be kept for not more than four months at
cated parts may be used as test specimens. On such specimens,
approximately 3 to 10 °C (37 to 50 °F). Use subcultures
observation of effect is limited to appearance, density of
incubated at 28 to 30 °C (82 to 86 °F) for 7 to 20 days in
growth,opticalreflectionortransmission,ormanualevaluation
preparing the spore suspension.
of change in physical properties such as stiffness.
6.4.1.2 Prepare a spore suspension of each of the five fungi
8.2 Film-forming materials such as coatings may be tested
by pouring into one subculture of each fungus a sterile 10-mL
in the form of films at least 50 by 25 mm (2 by 1 in.) in size.
portion of water or of a sterile solution containing 0.05 g/L of
Such films may be prepared by casting on glass and stripping
a nontoxic wetting agent such as sodium dioctyl sulfosucci-
after cure, or by impregnating (completely covering) filter
nate. Use a sterile platinum, plastic, or nichrome inoculating
paper or ignited glass fabric.
wire to gently scrape the surface growth from the culture of the
test organism.
8.3 For visual evaluation, three specimens shall be inocu-
6.4.2 Pour the spore charge into a sterile flask or tube
lated.Ifthespecimenisdifferentontwosides,threespecimens
containing 45 mLof sterile water with wetting agent and 10 to
of each, face up and face down, shall be tested.
15 solid glass beads. Cap and shake the flask vigorously to
NOTE 3—In devising a test program intended to reveal quantitative
liberate the spores from the fruiting bodies and to break the
changes occurring during and after fungal attack, an adequate number of
spore clumps.
specimens should be evaluated to establish a valid value for the original
6.4.3 Alternatively, the spore charge can be poured into a
property. If five replicate specimens are required to establish a tensile
strength of a film material, the same number of specimens shall be
sterile glass tissue grinder and gently ground to break up the
removed and tested for each exposure period. It is to be expected that
spore clumps and liberate the spores from the fruiting bodies.
values of physical properties at various stages of fungal attack will be
6.4.4 Filter the shaken or ground suspension through a thin
variable; the values indicating the greatest degradation are the most
layer of sterile glass wool in a glass funnel into a sterile flask
significant (see 4.4). Reference (2) may be used as a guide.
in order to remove mycelial fragments.
6.4.5 Centrifuge the filtered spore suspension aseptically,
9. Procedure
and discard the supernatant liquid. Resuspend the residue in an
9.1 Inoculation—Poursufficientnutrient-saltsagarintosuit-
aliquot of sterile water and centrifuge.
able sterile dishes (see 5.1) to provide a solidified agar layer
6.4.6 If large mycelia fragments or clumps of agar were
1 1
from3to6mm( ⁄8 to ⁄4 in.) in depth. After the agar is
dislodgedduringtheharvesting,washthesporesinthismanner
solidified, place the specimens on the surface o
...
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