1、Designation: G21 13Standard Practice forDetermining Resistance of Synthetic Polymeric Materials toFungi1This standard is issued under the fixed designation G21; the number immediately following the designation indicates the year of originaladoption or, in the case of revision, the year of last revis
2、ion. A number in parentheses indicates the year of last reapproval. A superscriptepsilon () 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.1. Scope1.1 This practice covers determination of the
3、effect of fungion the properties of synthetic polymeric materials in the formof molded and fabricated articles, tubes, rods, sheets, and filmmaterials. Changes in optical, mechanical, and electrical prop-erties may be determined by the applicable ASTM methods.1.2 The values stated in SI units are to
4、 be regarded as thestandard. The inch-pound units given in parentheses are forinformation only.1.3 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health pr
5、actices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D149 Test Method for Dielectric Breakdown Voltage andDielectric Strength of Solid Electrical Insulating Materialsat Commercial Power FrequenciesD150 Test Methods for AC Loss Cha
6、racteristics and Permit-tivity (Dielectric Constant) of Solid Electrical InsulationD257 Test Methods for DC Resistance or Conductance ofInsulating MaterialsD495 Test Method for High-Voltage, Low-Current, Dry ArcResistance of Solid Electrical Insulation (Withdrawn2013)3D618 Practice for Conditioning
7、Plastics for TestingD638 Test Method for Tensile Properties of PlasticsD747 Test Method for Apparent Bending Modulus of Plas-tics by Means of a Cantilever BeamD785 Test Method for Rockwell Hardness of Plastics andElectrical Insulating MaterialsD882 Test Method for Tensile Properties of Thin PlasticS
8、heetingD1003 Test Method for Haze and Luminous Transmittanceof Transparent PlasticsD1708 Test Method for Tensile Properties of Plastics by Useof Microtensile SpecimensE96/E96M Test Methods for Water Vapor Transmission ofMaterialsE308 Practice for Computing the Colors of Objects by Usingthe CIE Syste
9、m2.2 TAPPI Standard:Test Method T 451-CM-484 Flexural Properties of Paper42.3 Federal Standards:FED STD 191 Method 5204 Stiffness of Cloth, Directional;Self Weighted Cantilever Method5FED STD 191 Method 5206 Stiffness of Cloth Drape andFlex; Cantilever Bending Method53. Summary of Practice3.1 The pr
10、ocedure described in this practice consists ofselection of suitable specimens for determination of pertinentproperties, inoculation of the specimens with suitableorganisms, exposure of inoculated specimens under conditionsfavorable to growth, examination and rating for visual growth,and removal of t
11、he specimens and observations for testing,either before cleaning or after cleaning and reconditioning.NOTE 1Since the procedure involves handling and working withfungi, it is recommended that personnel trained in microbiology performthe portion of the procedure involving handling of organisms andino
12、culated specimens.1This practice is under the jurisdiction of ASTM Committee G03 on Weatheringand Durability and is the direct responsibility of Subcommittee G03.04 onBiological Deterioration.Current edition approved Nov. 1, 2013. Published December 2013. Originallyapproved in 1961. Last previous ed
13、ition approved in 2009 as G21 09. DOI:10.1520/G0021-13.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3The l
14、ast approved version of this historical standard is referenced onwww.astm.org.4Available from Technical Association of the Pulp and Paper Industry (TAPPI),15 Technology Parkway South, Norcross, GA 30092, http:/www.tappi.org.5Available from Standardization Documents Order Desk, DODSSP, Bldg. 4,Sectio
15、n D, 700 Robbins Ave., Philadelphia, PA 19111-5098, http:/dodssp.daps.dla.mil.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States14. Significance and Use4.1 The synthetic polymer portion of these materials isusually fungus-resistant in th
16、at it does not serve as a carbonsource for the growth of fungi. It is generally the othercomponents, such as plasticizers, cellulosics, lubricants,stabilizers, and colorants, that are responsible for fungus attackon plastic materials. To assess materials other than plastics, useof this test method s
17、hould be agreed upon by all partiesinvolved. It is important to establish the resistance to microbialattack under conditions favorable for such attack, namely, atemperature of 2 to 38C (35 to 100F) and a relative humidityof 60 to 100 %.4.2 The effects to be expected are as follows:4.2.1 Surface atta
18、ck, discoloration, loss of transmission(optical), and4.2.2 Removal of susceptible plasticizers, modifiers, andlubricants, resulting in increased modulus (stiffness), changesin weight, dimensions, and other physical properties, anddeterioration of electrical properties such as insulationresistance, d
19、ielectric constant, power factor, and dielectricstrength.4.3 Often the changes in electrical properties are due prin-cipally to surface growth and its associated moisture and to pHchanges caused by excreted metabolic products. Other effectsinclude preferential growth caused by nonuniform dispersiono
20、f plasticizers, lubricants, and other processing additives.Attack on these materials often leaves ionized conductingpaths. Pronounced physical changes are observed on productsin film form or as coatings, where the ratio of surface tovolume is high, and where nutrient materials such as plasticiz-ers
21、and lubricants continue to diffuse to the surface as they areutilized by the organisms.4.4 Since attack by organisms involves a large element ofchance due to local accelerations and inhibitions, the order ofreproducibility may be rather low. To ensure that estimates ofbehavior are not too optimistic
22、, the greatest observed degree ofdeterioration should be reported.4.5 Conditioning of the specimens, such as exposure toleaching, weathering, heat treatment, etc., may have significanteffects on the resistance to fungi. Determination of these effectsis not covered in this practice.5. Apparatus5.1 Gl
23、asswareGlass or plastic vessels are suitable forholding specimens when laid flat. Depending on the size of thespecimens, the following are suggested:5.1.1 For specimens up to 75 mm (3 in.) in diameter, 100 by100 mm (414 by 414 in.) plastic boxes6or 150-mm (6-in.)covered Petri dishes, and5.1.2 For 75
24、 mm (3 in.) and larger specimens, such astensile and stiffness strips, large Petri dishes, trays of borosili-cate glass, or baking dishes up to 400 by 500 mm (16 by 20 in.)in size, covered with squares of window glass.5.2 IncubatorIncubating equipment for all test methodsshall maintain a temperature
25、 of 28 to 30C (82.4 to 86F) anda relative humidity not less than 85 %. Automatic recording ofwet and dry-bulb temperature is recommended.6. Reagents and Materials6.1 Purity of ReagentsReagent grade chemicals shall beused in all tests. Unless otherwise indicated, it is intended thatall reagents shall
26、 conform to the specifications of the Commit-tee on Analytical Reagents of the American Chemical Society,where such specification are available.7Other grades may beused, provided it is first ascertained that the reagent is ofsufficiently high purity to permit its use without lessening theaccuracy of
27、 the determination.6.2 Purity of WaterUnless otherwise indicated, referencesto water shall be understood to mean distilled water or water ofequal or higher purity.6.3 Nutrient-Salts AgarPrepare this medium by dissolvingin 1 L of water the designated amounts of the followingreagents:Potassium dihydro
28、gen orthophosphate (KH2PO4) 0.7 gMagnesium sulfate (MgSO47H2O) 0.7 gAmmonium nitrate (NH4NO3) 1.0 gSodium chloride (NaCl) 0.005 gFerrous sulfate (FeSO47H2O) 0.002 gZinc sulfate (ZnSO47H2O) 0.002 gManganous sulfate (MnSO4H2O) 0.001 gAgar 15.0 gPotassium monohydrogen orthophosphate (K2HPO4) 0.7 g6.3.1
29、 Sterilize the test medium by autoclaving at 121C(250F) for 20 min. Adjust the pH of the medium by theaddition of 0.01 N NaOH solution so that after sterilization thepH is between 6.0 and 6.5.6.3.2 Prepare sufficient medium for the required tests.6.3.3 Nutrient Salts BrothPrepare using the formula i
30、n6.3, omitting the agar. Broth may be filter sterilized to avoid theprecipitation of the salts that occurs with autoclaving.6.4 Mixed Fungus Spore Suspension:NOTE 2Since a number of other organisms may be of specific interestfor certain final assemblies or components, such other pure cultures oforga
31、nisms may be used if agreed upon by the purchaser and themanufacturer of the plastic. Reference (1)8illustrates such a choice.6Available from Tri-State, Inc., Henderson, KY.7Reagent Chemicals, American Chemical Society Specifications, AmericanChemical Society, Washington, DC. For suggestions on the
32、testing of reagents notlisted by the American Chemical Society, see Analar Standards for LaboratoryChemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeiaand National Formulary, U.S. Pharmaceutical Convention, Inc. (USPC), Rockville,MD.8The boldface numbers given in parentheses
33、refer to a list of references at theend of the practice.G211326.4.1 Use the following test fungi in preparing the cultures:Fungi ATCC No.AMYCO No.BAspergillus niger 9642 386Penicillium pinophilumC11797 391Chaetomium globosum 6205 459Trichoderma virensD9645 365Aureobasidium pullulans 15233 279cAAvail
34、able from American Type Culture Collection, 12301 Parklawn Drive,Rockville, MD 20852.BAvailable from Mycological Services, P.O. Box 1056, Crawfordsville, IN 47933.CHistorically known as P. funiculosm.DHistorically known as Gliocladium virens.6.4.1.1 Maintain cultures of these fungi separately on ana
35、ppropriate medium such as potato dextrose agar. The stockcultures may be kept for not more than four months atapproximately 3 to 10C (37 to 50F). Use subculturesincubated at 28 to 30C (82 to 86F) for 7 to 20 days inpreparing the spore suspension.6.4.1.2 Prepare a spore suspension of each of the five
36、 fungiby pouring into one subculture of each fungus a sterile 10-mLportion of water or of a sterile solution containing 0.05 g/L ofa nontoxic wetting agent such as sodium dioctyl sulfosucci-nate. Use a sterile platinum or nichrome inoculating wire togently scrape the surface growth from the culture
37、of the testorganism.6.4.2 Pour the spore charge into a sterile 125-mL glass-stoppered Erlenmeyer flask containing 45 mL of sterile waterand 10 to 15 solid glass beads, 5 mm in diameter. Shake theflask vigorously to liberate the spores from the fruiting bodiesand to break the spore clumps.6.4.3 Alter
38、natively, the spore charge can be poured into asterile glass tissue grinder and gently ground to break up thespore clumps and liberate the spores from the fruiting bodies.6.4.4 Filter the shaken or ground suspension through a thinlayer of sterile glass wool in a glass funnel into a sterile flaskin o
39、rder to remove mycelial fragments.6.4.5 Centrifuge the filtered spore suspension aseptically,and discard the supernatant liquid. Resuspend the residue in analiquot of sterile water and centrifuge.6.4.6 If large mycelia fragments or clumps of agar weredislodged during the harvesting, wash the spores
40、in this mannerthree times to remove possible nutrient carryover from theoriginal cultures. Dilute the final washed residue with sterilenutrient-salts solution (see 6.3.3) in such a manner that theresultant spore suspension shall contain 1 000 000 6 200 000spores/mL as determined with a counting cham
41、ber.6.4.7 Repeat this operation for each organism used in thetest and blend equal volumes of the resultant spore suspensionto obtain the final mixed spore suspension.6.4.8 The mixed spore suspension may be prepared fresheach day or may be held in the refrigerator at 3 to 10C (37 to50F) for not more
42、than four days. The individual sporesuspensions may be held in the refrigerator at 3 to 10C (37 to50F) for not more than fourteen days.7. Viability Control7.1 With each daily group of tests place each of three piecesof sterilized filter paper, 25 mm (1 in.) square, on hardenednutrient-salts agar in
43、separate Petri dishes. Inoculate these withthe spore suspension by spraying the suspension from asterilized atomizer9so that the entire surface is moistened withthe spore suspension. Incubate these at 28 to 30C (82 to 86F)at a relative humidity not less than 85 % and examine themafter 14 days incuba
44、tion. There shall be copious growth on allthree of the filter paper control specimens. Absence of suchgrowth requires repetition of the test.8. Test Specimens8.1 The simplest specimen may be a 50 by 50-mm (2 by2-in.) piece, a 50-mm (2-in.) diameter piece, or a piece (rod ortubing) at least 76 mm (3
45、in.) long cut from the material to betested. Completely fabricated parts or sections cut from fabri-cated parts may be used as test specimens. On such specimens,observation of effect is limited to appearance, density ofgrowth, optical reflection or transmission, or manual evaluationof change in phys
46、ical properties such as stiffness.8.2 Film-forming materials such as coatings may be testedin the form of films at least 50 by 25 mm (2 by 1 in.) in size.Such films may be prepared by casting on glass and strippingafter cure, or by impregnating (completely covering) filterpaper or ignited glass fabr
47、ic.8.3 For visual evaluation, three specimens shall be inocu-lated. If the specimen is different on two sides, three specimensof each, face up and face down, shall be tested.NOTE 3In devising a test program intended to reveal quantitativechanges occurring during and after fungal attack, an adequate
48、number ofspecimens should be evaluated to establish a valid value for the originalproperty. If five replicate specimens are required to establish a tensilestrength of a film material, the same number of specimens shall beremoved and tested for each exposure period. It is to be expected thatvalues of
49、 physical properties at various stages of fungal attack will bevariable; the values indicating the greatest degradation are the mostsignificant (see 4.4). Reference (2) may be used as a guide.9. Procedure9.1 InoculationPour sufficient nutrient-salts agar into suit-able sterile dishes (see 5.1) to provide a solidified agar layerfrom3to6mm(18 to14 in.) in depth. After the agar issolidified, place the specimens on the surface of the agar.Inoculate the surface, including the surface of the testspecimens, with the composite spore suspension by sprayin
