1、Designation: G 160 03Standard Practice forEvaluating Microbial Susceptibility of Nonmetallic MaterialsBy Laboratory Soil Burial1This standard is issued under the fixed designation G 160; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revisi
2、on, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This practice is limited to the method of conducting anevaluation of a nonmetallic materials microbio
3、logical suscep-tibility when in contact with the natural environment of thesoil. This practice is intended for use on solid material testspecimens that are no larger than approximately 2 cm (34 in.)thick and 100 cm2(20 in.2) or on film forming materials suchas coatings which may be tested in the for
4、m of films at least 50by 50 mm (2 by 2 in.) in size. This practice may be applied toarticles that do not spend the majority of their service life insoil.1.2 A wide variety of properties may be affected by micro-bial attack depending on material or item characteristics.Standard methods (where availab
5、le) should be used for eachdifferent property to be evaluated. This practice does notattempt to enumerate all of the possible properties of interestnor specify the most appropriate test for those properties. Testmethods must, however, be appropriate to the material beingtested.1.3 It is recommended
6、that this practice be combined withappropriate environmental exposures (for example, sunlightsimulating weathering devices, the hydrolytic effects of ex-tended aqueous contact, or extraneous nutrients) or fabricationinto articles (for example, adhesive bonding of seams) whichmay promote microbiologi
7、cal susceptibility during the servicelife of the material.1.4 The values given in parentheses are provided for infor-mation purposes only.2. Significance and Use2.1 These results may be used to compare the susceptibilityof materials when exposed to this test procedure.2.2 Microbiological susceptibil
8、ity may be reflected by anumber of changes including staining, weight loss, or reductionin tensile or flexural strength.2.3 This practice may be considered an inoculation with amixed culture of fungi and bacteria.3. Soil3.1 Composition Soil shall be composed of equal parts offertile topsoil (soil wi
9、th a high clay content should not beused), well-rotted and shredded horse manure, and coarse sand(10 to 40 mesh).3.2 MixingThe soil composition of 3.1 should be pre-pared by simple mixing and sifting through14-in. mesh screen.3.3 AgingThe mixture is aged for three months andresifted twice at four-we
10、ek intervals during the three months.After three months, a viability control of untreated cotton cloth,400 to 475 g/m2(12 to 14 oz/yd2), buried in the soil shall havea tensile strength loss of at least 50 % after five days.NOTE 1The soil mixture may be used for sequential tests as long asthe cotton
11、cloth control degrades within the specified time period.3.4 pHThe soil shall have a pH between 6.5 to 7.5,checked periodically, and maintained by the addition of groundlimestone to raise the pH or flowers of sulfur to lower the pH.The soil pH may be taken by dispersing 1 weight part soil in 20parts
12、of water, shaking or stirring, then allowing the mix tosettle for 1 h. The pH is measured with indicator paper,electrodes, or by titration.3.5 MoistureThe soil shall be maintained at between 20and 30 % moisture, based on the dry weight of the soil. (Thepercent moisture is calculated by weighing appr
13、oximately 50mL of a representative portion and taking the portion toconstant weight by placing the soil in an oven at a temperatureof 101 to 106C.) Water lost during use as a result ofevaporation shall be replaced without deforming the soil bed. Ifthe surrounding atmosphere is maintained at 85 to 95
14、 %relative humidity, this loss is negligible, however, the moisturelevel should be periodically measured.1This practice is under the jurisdiction of Committee G3 on Weathering andDurability and is the direct responsibility of Subcommittee G03.04 on BiologicalDeterioration.Current edition approved De
15、c. 10, 2003. Published January 2004. Originallyapproved in 1998. Last previous edition approved in 1998 as G 16098.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.4. Apparatus4.1 Soil Container The container shall be any material ofs
16、uitable mechanical strength and chemical/microbial resistanceand, if porous, shall be lined with impermeable material. Itshall be of any size that is convenient to handle and having adepth of at least 12.7 cm (5 in.).4.2 External EnvironmentAn apparatus capable of main-taining a temperature of 30 6
17、2C (86 6 3.6F) and a relativehumidity to 85 to 95 %, into which the assembled container isinserted, is necessary. An incubator or controlled tropicalchamber is adequate.5. Test Specimens5.1 Completely fabricated parts or sections cut from fabri-cated parts may be used as test specimens. The simplest
18、specimen may be a 50- by 50-mm (2- by 2-in.) piece, a 50-mm(2-in.) diameter piece, or a piece (rod or tubing) at least 76 mm(3 in.) long cut from the material to be tested.5.2 Film-forming materials such as coatings may be testedin the form of films at least 50 by 50 mm (2 by 2 in.) in size.Such fil
19、ms may be prepared by casting on glass and strippingafter cure or by impregnating (completely covering) filter paperor ignited glass fabric.5.3 For visual evaluation, a minimum of three test speci-mens shall be used.5.4 In devising a test program intended to reveal quantita-tive changes occurring du
20、ring and after exposure, an adequatenumber of specimens should be evaluated to establish a validvalue for the original property. For example, if five replicatetest specimens are required to establish a tensile strength of afilm material, at least that number of test specimens shall beremoved and tes
21、ted for each exposure period. It is to beexpected that values of physical or mechanical properties atvarious stages of fungal attack will be variable. The ASTMManual 72may be used as a guide.6. Viability6.1 The viability must be recommended as in 3.3 concurrentwith the test specimen and exposed cons
22、istent with the testspecimen duration and number of test specimens.7. Replicates7.1 A minimum of four replicates are recommended.8. Duration8.1 The exposure period for soil burial, unless otherwisespecified, shall be for a minimum of 60 days.NOTE 2The test specimens cannot be removed for the soil be
23、d, oncethey have been buried, until the exposure period has been completed.Disturbing the soil bed in such a manner as removing the test specimensmay affect the growth of soil microbes and thus cause inconsistent results.A separate set of specimens must be used for each exposure interval (forexample
24、, a set of replicates for 30, 60, and 90 days as needed).9. Calculation and Interpretation of Results9.1 VisualAt the end of the exposure period, the speci-mens shall be removed from the soil bed and conditionedaccording to methods appropriate to the material being tested.For visual evaluation, the
25、material is rinsed under a stream oftap water while gently rubbing between fingers to remove soiland air-drying at 20C (68F) for minimum amount of time.Alternatively, the material may be gently vacuumed or verygently air-brushed.9.2 Microbial staining shall be evaluated as follows:Observed Growth or
26、 Stain RatingNone 0Trace (less than 10 % coverage) 1Light (10 to 30 % coverage) 2Moderate (30 to 60 % coverage) 3Heavy (60 % to complete coverage) 49.3 Property Changes Physical and mechanical changessuch as tensile strength, flexibility, weight loss, or other tests,may be performed as described in
27、appropriate ASTM or othertest methods. Tests shall be conducted on unexposed andexposed specimens for the purpose of comparison in determin-ing the extent of microbial degradation of the test material.9.4 Calculate the change in property for each replicatespecimen using one of the following equation
28、s:Ce, i5Xe, i2 Xo(1)Ce, i5 Xe, i2 Xf(2)where:Xe, i= measured property of each exposed specimen,Xo= mean of property from initial measurements onunexposed specimens, andXf= mean of property from measurements on file speci-mens.9.5 Use the following equation to determine the meanchange in property:C 5
29、(i 5 1nCe, in(3)where:n = number or exposed specimens.9.6 Use the following equation to determine the standarddeviation of the change in property:n (4)Sc5(Ci2C !2n 2 110. Report10.1 Report the following information: age of bed, speci-men size, number of replicates, performance of viabilitycontrol, v
30、isual staining in accordance with 9.1 and 9.2 orproperty change in accordance with 9.3, duration of burial, andany specific measurements requested.10.2 Satisfactory or unsatisfactory performance of a mate-rial is dependent on the applicable standard for that material ormethods agreed upon between th
31、e investigators.2Manual on Presentation of Data and Control Chart Analysis, 6th ed., Manual7, American Society for Testing and Materials, 1990.G16003211. Precision and Bias11.1 A precision and bias statement cannot be made at thistime.12. Keywords12.1 biodegradeable; biological deterioration; deface
32、ment;disfigurement; fungal resistance; fungi; laboratory soil culture;microbial susceptibility; microbiological deterioration; mil-dew; mixed microbial innoculum; mold growth; soilenvironmentASTM International takes no position respecting the validity of any patent rights asserted in connection with
33、 any item mentionedin this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the riskof infringement of such rights, are entirely their own responsibility.This standard is subject to revision at any time by the responsible techni
34、cal committee and must be reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standardsand should be addressed to ASTM International Headquarters. Your comments will receive careful consideratio
35、n at a meeting of theresponsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you shouldmake your views known to the ASTM Committee on Standards, at the address shown below.This standard is copyrighted by ASTM International, 100 Barr Harb
36、or Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org).G160033
