1、Designation: F2466 10Standard Practice forDetermining Silicone Volatiles in Silicone Rubber forTransportation Applications1This standard is issued under the fixed designation F2466; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, t
2、he year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This practice covers a means to determine the percentsilicone-producing volatiles present in heat-cured sil
3、iconerubber and room temperature-cured silicones (RTV).1.2 Silicone-producing volatiles contribute to fouling ofoxygen sensor systems used in the control of vehicle emis-sions.1.3 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsib
4、ility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D3182 Practice for RubberMaterials, Equipment, andProcedures for Mixing Standard Compounds and P
5、repar-ing Standard Vulcanized SheetsE177 Practice for Use of the Terms Precision and Bias inASTM Test MethodsE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method3. Summary of Practice3.1 This practice consists of four (4) basic steps: (1) thesilicone is cu
6、red to its elastomeric form, (2) the volatiles areextracted from the cured material, (3) the extract is separatedand measured by gas chromatography (GC), and (4) the GCresults are quantified using a siloxane calibration.4. Significance and Use4.1 Use of this practice in conjunction with realistic ma
7、xi-mum volatility tolerance level can help minimize the risk ofoxygen sensor dysfunction from formed-in-place-sealants intransportation applications. This practice provides a method fordetermination of percentage volatiles in silicone elastomers.The volatile silicones from a commercial silicone are
8、primarilycyclo dimethyl-siloxane. Other species present having GCretention times similar to those of the cyclics are assumed to besilicone as well.5. Apparatus5.1 Gas Chromatograph, fused silica capillary column sys-tem equipped with a flame ionization detector, split-typecapillary column injector,
9、temperature programming capabilityand an appropriate data recording system. An alternative unitmay be an equivalent instrument equipped with a thermalconductivity detector, or as agreed upon between producer anduser. Specific column and operating conditions should beselected to optimize instrument r
10、esponse and chromatographicresolution, particularly separation of the internal standard fromextracted sample components.5.2 Column, suggested to be used is 30 to 60 m by 0.25 mmwith 0.25 to 1.5 m DB-1 or DB-5 fused silica capillarycolumn or equivalent.5.3 Operating conditions are:5.3.1 Column50 to 3
11、20C at 10C/min (a post-analysisperiod may be required to elute higher boiling componentsprior to subsequent analyses).5.3.2 Injector290C.5.3.3 Detector325C.5.3.4 Sample Size1 L.5.3.5 Injector Split Ratio2:1 to 50:1 (adjusted as needed).5.3.6 Helium or Nitrogen, for the carrier gas.5.3.7 Carrier Gas
12、Flow Velocity1 to 2 mL/min (adjustedas needed for column dimensions).5.4 Humidity Chamber, or controlled lab environment.5.5 Wrist-Action Mechanical Shaker.5.6 Analytical Balance, with glass draft shield capable of0.0001 g accuracy.5.7 30-mL Vials, flint glass, with screw cap (polyethylenelined).5.8
13、 Syringe, capable of accurately delivering 20 6 0.1 L(no plastic elements used due to solvents used).1This practice is under the jurisdiction ofASTM Committee F03 on Gaskets andis the direct responsibility of Subcommittee F03.50 on Analytical Test Methods.Current edition approved May 1, 2010. Publis
14、hed June 2010. Originallyapproved in 2005. Last previous edition approved in 2005 as F2466 05. DOI:10.1520/F2466-10.2For 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
15、the standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.5.9 Solvents and standards used are pentane (99 %) anddodecane (99 %), both spectral grade.5.10 Rigid Plates (Glass or Aluminum),
16、0.90 mm thick, forcutting the wet formed-in-place sealant.5.11 Automated devices shall be used for measuring andcalculating peaks.6. Test Specimens6.1 Heat-cured silicone rubber samples shall be procuredfrom either actual production parts, or shall be compression-molded ASTM tensile plaques (Practic
17、e D3182, 2.0 6 0.2 mmthick). Cure conditions of the tensile plaques shall mirror cureconditions used on the production parts. If actual productionparts are used to obtain test samples, best practice would be tocut sample so that it is not thicker than the above stated tensileplaque thickness.6.2 Roo
18、m temperature-vulcanized (RTV) samples shall beprepared by spreading the liquid using a suitable device, intoconsistent 0.90 6 0.20 mm plaques. Avoid entrapped air andknit lines when preparing the sample.6.3 Three 1-g samples shall be cut from the plaque. Thesesamples shall be taken from near one co
19、rner, at the center of theplaque, and near the corner at a diagonal from the first.7. Standard Solutions37.1 Add 0.1 g (weighed to the nearest 0.1 mg) of each purecyclic (98 %) to 1.0 g of dodecane (99 %) (weighed to thenearest 0.1 mg). Ten millilitres 6 0.1 mL pentane is added andthe container is s
20、ealed to prevent leakage/evaporation. Newstandard mixtures should be prepared if existing one is morethan seven (7) days old.7.2 Calibration of the standard solution is achieved byinjecting 1 L (need verify use with SE 30 column will needto attenuate response or dilute solution) standard solutionsam
21、ple. Response factors for the individual cyclics are calcu-lated using the following equation:RfDn 5Wt DnADn*ADoDWtDoD(1)where:Rf = response factorDn = the cyclic siloxane species from a 4 member to a10 member ringRfDn = the response factor for each siloxane speciesfrom4to10WtDn = the weight of each
22、 siloxane species from 4 to 10used in the standard solutionADn = the area under the curve for each siloxanespecies from 4 to 10DoD = the dodecane standard, which is arbitrarily givena response factor of “1” (one), and is used as thebasis for calculating the response factors of thevarious know and un
23、know siloxane speciesADoD = the area under the curve for the dodecane stan-dardWtDoD = the weight of the dodecane used in the standardsolutions7.3 Response factors for cyclic species vary in a relativelylinear manner from D5through D10, so that response factors forcyclics not in the standard solutio
24、n can be calculated from theknown response factors of the cyclics in the standard solution.A sample calculation for response factors of standards avail-able, and a Linear Least Squares Analysis to determineresponse factors of cyclics that are unavailable can be found inAppendix X1.7.4 All of the unk
25、nowns that appear in the analysis (betweenD4and D10) are assumed to be dimethyl siloxanes. Allunknowns are given, as response factors, the average responsefactor calculated for the difunctional cyclosiloxane monomersD4through D10.8. Conditioning8.1 Allow RTV samples to cure for 24 h, but not to exce
26、ed72 h at 25C and 50 6 10 % relative humidity.9. Procedure9.1 ExtractionPre-weigh each cured sample to 1.0 6 0.2g (record weight to the nearest 0.0001 g) and set aside.9.2 Weigh 0.010 6 0.005 g of dodecane (record weight tothe nearest 0.0001 g) and place sample into the 30-mL vial. Tothis add 10 mL
27、of pentane. Immediately place the pre-weighedsample into the vial, and seal the container to prevent leakage/evaporation. Weight precision of the dodecane and test sampleare extremely important for reproducible results. The samplevial is placed on a wrist shaker for 16 h.NOTE 1The sequence is import
28、ant due to the volatility of the solvents.used.NOTE 2See 10.1.1 regarding dodecane measurement.9.3 Inject 1 to 5 L into the GC injection port. (Injectionvolume is dependant on the injector split ratio).9.4 After the elution is complete (about 35 min) identify thepeaks and quantify them by integratio
29、n using the followingequations (sample calculations are shown in Appendix X2):%Dn 5RfDn * ADnADoD*WtDoDSaWt* 100 (2)whereSaWt = the weight of the silicone part9.4.1 Perform Eq 2 for D4through D10.% Un 5AveRfDn * AUnADoD*WtDoDSaWt* 100 (3)where:Un = the unknown cyclic siloxanes in the sampleAveRfDn =
30、 the average of the response factors from D3toD109.4.2 Perform Eq 3 for all unknowns that elute between D4and D10.3The sole source of supply of the standards solutions known to the committee atthis time is Ohio Valley Specialty Chemicals, 115 Industrial Road, Marietta, OH,45750, 1-800-729-6972, Cata
31、log number 34569/Cyclic Standard Kit D3 throughD10. If you are aware of alternative suppliers, please provide this information toASTM International Headquarters. Your comments will receive careful consider-ation at a meeting of the responsible technical committee,1which you may attend.F2466 1029.4.3
32、 % Siloxane Volatiles = Sum of % cyclics D4throughD10and sum of % unknowns eluting from D4through D10.NOTE 3Silicone volatiles below D5may not be detected at theircorrect levels due to their loss from the sealant as it cures for 24 h at 25Cand 50 % relative humidity. Dodecane can mask D5forms and th
33、ebeginning of the first unknown. Any D3not lost would be masked byimpurities in pentane. Weight precision is extremely important if theresults are to be reproducible.10. Potential Failure Modes of Test Procedure10.1 Methods/techniques of weighing can be a major sourceof error. Its imperative that th
34、e technician be as exacting aspossible when weighing the following materials:(1) Each standard cyclic siloxane species,(2) Dodecane added to standard solutions, and to extractionsample vials, and(3) Each cut test sample to be added to extraction vial.10.1.1 In order to reduce error associated with w
35、eighing thesmall quantity of dodecane directly into the sample vial, it isrecommended to first prepare a standard solution using a largerdodecane weight. This is done by weight out approximately 0.1g dodecane (record weight to the nearest 0.0001g) into a10-mL classAvolumetric flask. Dilute to the li
36、ne with pentane,and calcualte the actual concentration per mL of dodecane,based on the previously recorded weight. One millilitre (1 mL)of this standard solution is added to each sample vial using aHamilton pipette.10.2 Loss of Small Amounts of DoD From Extraction VialDue to Incidental SplashInciden
37、tal fluid loss due to splashwhen adding dodecane, pentane, and pre-weighed siliconesample to extraction vial will greatly affect results. Care shouldbe taken when adding materials to extraction vial, and until capis tightly sealed. Any loss of material, no matter how small,must result in discarding
38、that sample and preparing a new one.11. Reporting11.1 Three data points shall be reported for each sample as% total volatiles.11.2 Final results for siloxane should be expressed as0.00 %. Report D4through D10for total volatiles as cyclicsplus unknowns (Un4through Un10).11.3 All observed and recorded
39、 data on which calculationsare based.11.4 Date of the test, cure conditions, and thickness of thesample.12. Precision and Bias412.1 The precision of this test method is based on aninterlaboratory study conducted in 2008. Each of four labora-tories tested five different materials for silicone volatil
40、es (theresults from these five tested in one of the laboratories wereunusable due to the utilization of improper response factors).Every “test result” represents an individual determination. Alllaboratories were asked to report three replicate results for eachsample. Except for the limited number of
41、 participating labora-tories, Practice E691 was followed for the design and analysisof the data.12.1.1 Repeatability limit (r)Two test results obtainedwithin one laboratory shall be judged not equivalent if theydiffer by more than the “r” value for that material; “r”istheinterval representing the cr
42、itical difference between two testresults for the same material, obtained by the same operatorusing the same equipment on the same day in the samelaboratory.12.1.1.1 Repeatability limits are listed in Table 1 below.12.1.2 Reproducibility limit (R)Two test results shall bejudged not equivalent if the
43、y differ by more than the “R” valuefor that material; “R” is the interval representing the criticaldifference between two test results for the same material,obtained by different operators using different equipment indifferent laboratories.12.1.2.1 Reproducibility limits are listed in Table 1 below.
44、12.1.3 The above terms (repeatability limit and reproduc-ibility limit) are used as specified in Practice E177.12.1.4 Any judgment in accordance with statements 12.1.1and 12.1.2 would normally have an approximate 95 % prob-ability of being correct; however, the precision statisticsobtained in this I
45、LS must not be treated as exact mathematicalquantities which are applicable to all circumstances and uses.The limited number of laboratories reporting results guaranteesthat there will be times when differences greater than predictedby the ILS results will arise, sometimes with considerablygreater o
46、r smaller frequency than the 95 % probability limitwould imply. Consider the repeatability limit and the repro-ducibility limit as general guides, and the associated probabil-ity of 95 % as only a rough indicator of what can be expected.12.2 BiasAt the time of the study, there was no acceptedreferen
47、ce material suitable for determining the bias for this testmethod, therefore no statement on bias is being made.12.3 The precision statement was determined through sta-tistical examination of 45 results, from three laboratories, onfive materials. These five materials were described as thefollowing:(
48、1) Material 1: Acetoxy RTV -Q3-7057LV(2) Material 2: Alkoxy RTV - 3-0115(3) Material 3: Amine RTV - A2000(4) Material 4: High viscosity Oxime - 5900(5) Material 5: Low Viscosity Oxime RTV - 591012.4 To judge the equivalency of two test results, it isrecommended to choose the material closest in char
49、acteristicsto the test material.4Supporting data have been filed at ASTM International Headquarters and maybe obtained by requesting Research Report RR:F03-1017.TABLE 1 Silicone Volatiles (%)Material AverageARepeatabilityStandardDeviationReproducibilityStandardDeviationRepeatabilityLimitReproducibilityLimitx SrSRrR1 0.286 0.038 0.099 0.107 0.2782 0.236 0.048 0.092 0.133 0.2583 0.216 0.035 0.059 0.098 0.1664 0.137 0.020 0.077 0.057 0.2165 0.171 0.023 0.077 0.063 0.215AThe average of the laboratories calculated averages.F2466 10313. Keywords13.1 percent
