1、Designation: F 2466 05Standard Practice forDetermining Silicone Volatiles in Silicone Rubber forTransportation Applications1This standard is issued under the fixed designation F 2466; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision,
2、 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 covers a means to determine the percentsilicone-producing volatiles present in heat-cured
3、siliconerubber 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 therespon
4、sibility 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:2D 3182 Practice for RubberMaterials, Equipment, andProcedures for Mixing Standard Compounds a
5、nd Prepar-ing Standard Vulcanized Sheets3. Summary of Practice3.1 This practice consists of four (4) basic steps: (1) thesilicone is cured 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
6、 GCresults are quantified using a siloxane calibration.4. Significance and Use4.1 Use of this practice in conjunction with realistic maxi-mum volatility tolerance level can help minimize the risk ofoxygen sensor dysfunction from formed-in-place-sealants intransportation applications. This practice p
7、rovides a method fordetermination of percentage volatiles in silicone elastomers.The volatile silicones from a commercial silicone are primarilycyclo dimethyl-siloxane. Other species present having GCretention times similar to those of the cyclics are assumed to besilicone as well.5. Apparatus5.1 Ga
8、s Chromatograph, equipped with a dual column, dualthermal conductivity detectors, differential flow control, lineartemperature programming capability, and an appropriate 1 mVpotentiometric recorder. An alternative unit may be the equiva-lent of a Hewlett Packard 5880A, equipped with a flameionizatio
9、n detector, or as agreed upon between producer anduser.5.2 Column, to be used with the first GC is 2.4 m by 0.32 cmstainless steel with a 5 % OV-101 coating and 80/100 Chro-mosorb W, HP. The HP 5880Atype GC uses a column 60 m by0.25 mm with 0.25-1 m DB-1 or SE30 fused silica capillarycolumn or equiv
10、alent.5.3 Operating conditions for first GC type are:5.3.1 Column50 to 320C at 10C/min.5.3.2 Injector290C.5.3.3 Detector290C.5.3.4 He Flow Velocity4 cm/s.5.3.5 Sample Size40 L.5.4 Operating conditions for the alternative GC type are:5.4.1 Column60 to 250C at 10C/min.5.4.2 Injector250C.5.4.3 Detector
11、300C.5.4.4 He Flow Velocity1-2 mL/min (column flow).5.4.5 Sample Size1 L.5.5 Helium or Nitrogen, for the carrier gas.5.6 Humidity Chamber, or controlled lab environment.5.7 Wrist-Action Mechanical Shaker.5.8 Analytical Balance, with glass draft shield capable of0.0001 g accuracy.5.9 30-mL Vials, fli
12、nt glass, with screw cap (polyethylenelined).5.10 Syringe, capable of accurately delivering 20 6 0.1 L(no plastic elements used due to solvents used).5.11 Solvents and standards used are pentane (99 %) anddodecane (99 %), both spectral grade.1This practice is under the jurisdiction ofASTM Committee
13、F03 on Gaskets andis the direct responsibility of Subcommittee F03.50 on Analytical Test Methods.Current edition approved March 1, 2005. Published April 2005.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of A
14、STMStandards volume information, refer to 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.5.12 Rigid Plates (glass or aluminum), 0.90 mm thick, forcutting the wet formed-in-place
15、 sealant.5.13 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 (Practice D 3182). Cure condi-tions of the tensile plaque
16、s shall mirror cure conditions used onthe production parts.6.2 Room 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
17、 cut from the plaque. Thesesamples shall be taken from near one corner, 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
18、). Ten millilitres 6 0.1 mL pentane is added andthe container is sealed to prevent evaporation. New standardmixtures should be prepared if existing one is more than seven(7) days old.7.2 Calibration of the standard solution is achieved usingone of the two operating conditions (dependent on the type
19、ofGC) described in 5.3 and inject 1 L (need verify use with SE30 column will need to attenuate response or dilute solution)standard solution sample. Response factors for the individualcyclics are calculated using the following equation:RfDn 5Amt. Dn in standard solutionArea Dn in chromatogramxArea d
20、odecane in chromatogramWt. dodecane in standard solution(1)7.3 Response factors for cyclic species vary in a relativelylinear manner from D5through D10, so that response factors forcyclics net in the standard solution can be calculated from theknown response factors of the cyclics in the standard so
21、lution.7.4 All of the unknowns 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
22、for 24 h, but not to exceed72 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 0.020 6 0.005 g of dodecane (record weight tothe nearest 0.0001 g) and place sample into the 30-m
23、L vial. Tothis add 10 mL of pentane. Immediately place the pre-weighedsample into the vial, and seal the container to prevent evapo-rative loss. Weight precision is extremely important for repro-ducible results. The sample vial is placed on a wrist shaker for16 h.NOTE 1The sequence is important due
24、to the volatility of the solvents.used.9.3 Inject 20 L into the GC injection port.9.4 After the elution is complete (about 35 min) identify thepeaks and quantify them by integration using the followingequations:%Dn 5RfDn Area Dn in chromatogram!Area dodecane in chromatogram!xWt. dodecane in sample!P
25、erform the calculation for D4 D10x 100 (2)% Unknown 5RfD4210Area unknown in chromatogram!Area dodecane in chromatogram!xWt. dodecane in sample!RfD12105 Average response factors of D4210x 100(3)9.4.1 Perform the calculation for all unknowns that elutebetween D4and D10.9.4.2 % Siloxane Volatiles = Sum
26、 of % cyclics D4-10andsum of % unknowns eluting from D4D10.NOTE 2Silicone 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 thebeginning of the first unknown. Any D3not
27、lost would be masked byimpurities in pentane. Weight precision is extremely important if theresults are to be reproducible.10. Reporting10.1 Three data points shall be reported for each sample as% total volatiles.10.2 Final results for siloxane should be expressed as0.00 %. Report D4through D10for t
28、otal volatiles as cyclicsplus unknowns (L4through L10).10.3 All observed and recorded data on which calculationsare based.10.4 Date of the test, cure conditions, and thickness of thesample.11. Keywords11.1 percent volatiles; silicone; transportation and oxygensensor systems3The sole source of supply
29、 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, Catalog number 34569/Cyclic Standard Kit D3 throughD10. If you are aware of alternative suppliers, please provide this information toASTM Intern
30、ational Headquarters. Your comments will receive careful consider-ation at a meeting of the responsible technical committee,1which you may attend.F2466052ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard.
31、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 technical committee and must be reviewed ev
32、ery 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 consideration at a meeting of theresponsible tech
33、nical 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 Harbor 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).F2466053
