1、Designation: D1278 91a (Reapproved 2011)Standard Test Methods forRubber from Natural SourcesChemical Analysis1This standard is issued under the fixed designation D1278; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of la
2、st 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 These test methods cover the sampling and chemicalanalysis of solid natural rubber in the forms supplied to therubber in
3、dustry.1.2 The analytical procedures appear in the following order:SectionsSampling 5Volatile Matter 6-8Dirt 9-13Ash 14-17Copper (Referee Colorimetric Method) 18-22Copper (Alternative Colorimetric Method) 23-27Copper (Alternative Flame Atomic Absorption Method) 28Manganese (Colorimetric Method) 29-3
4、3Manganese (Alternative Flame Atomic Absorption Method) 34Iron (Colorimetric Method) 35-39Acetone Extract 40-41Rubber Hydrocarbon 42-43Nitrogen 44-451.3 The values stated in SI units are to be regarded as thestandard. The values in parentheses are for information only.1.4 This standard does not purp
5、ort 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 practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D29
6、7 Test Methods for Rubber ProductsChemicalAnaly-sisD1193 Specification for Reagent WaterD1485 Practice for Rubber from Natural SourcesSampling and Sample PreparationD3533 Test Method for RubberNitrogen Content3D4004 Test Methods for RubberDetermination of MetalContent by Flame Atomic Absorption (AAS
7、) AnalysisD4483 Practice for Evaluating Precision for Test MethodStandards in the Rubber and Carbon Black ManufacturingIndustriesE11 Specification for Woven Wire Test Sieve Cloth and TestSievesE131 Terminology Relating to Molecular Spectroscopy3. Significance and Use3.1 These test methods are intend
8、ed for quality controlacceptance of natural rubber and may be used for refereepurposes.4. Reagents4.1 Purity of ReagentsReagent grade chemicals shall beused in all tests. Unless otherwise indicated, it is intended thatall reagents shall conform to the specifications of the Commit-tee on Analytical R
9、eagents of the American Chemical Society,where such specifications are available.4Other grades may beused, provided it is first ascertained that the reagent is ofsufficiently higher purity to permit its use without lessening theaccuracy of the determination.4.2 Purity of WaterUnless otherwise indica
10、ted, referencesto water shall be understood to mean reagent water conformingto Specification D1193.5. Sampling5.1 A lot of natural rubber shall be sampled, the sampleprepared for test, and the acceptability of the lot determinedfrom tests on the sample in accordance with Test MethodsD1485.VOLATILE M
11、ATTER6. Procedure6.1 Weigh a 10 to 12-g specimen of homogenized rubber tothe nearest 1 mg and then dry it in a circulating-air oven at 1006 5C to constant mass. If it is suspected that volatile1These test methods are under the jurisdiction of ASTM Committee D11 onRubber and are the direct responsibi
12、lity of Subcommittee D11.22 on NaturalRubber.Current edition approved Nov. 1, 2011. Published January 2012. Originallyapproved in 1953. Last previous edition approved in 2007 as D1278 91a (2007).DOI: 10.1520/D1278-91AR11.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact
13、 ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Withdrawn. The last approved version of this historical standard is referencedon www.astm.org.4Reagent Chemicals, American Chemical Society
14、 Specifications, AmericanChemical Society, Washington, DC. For Suggestions on the testing of reagents notlisted by the American Chemical Society, see Annual Standards for LaboratoryChemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeiaand National Formulary, U.S. Pharmacopeial
15、Convention, Inc. (USPC), Rockville,MD.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.hydrocarbon oils are present, they should be determined byheating the rubber in a circulating-air oven at 160 6 5C toconstant weight. The drying is
16、 facilitated by cutting the rubberinto 25-mm strips having a maximum width and thickness of2.5 by 1.25 mm or by passing it through a laboratory mill witha clearance between rolls set at 0.5 6 0.1 mm (0.020 6 0.004in.). Keep the dried specimen in a covered weighing vessel orin a desiccator after its
17、removal from the oven until it is readyto be weighed.7. Calculation7.1 Calculate the percentage of volatile matter as follows:V 5 1 2 B 3 D!/A 3 C!# 3 100 (1)where:V = percentage of volatile matter,A = mass of piece taken from bale,B = mass of piece after homogenizing,C = mass of specimen before ove
18、n drying, andD = mass of specimen after oven drying.8. Precision and Bias8.1 Task groups for the purpose of obtaining precision andbias data in accordance with Practice D4483 are being orga-nized and precision and bias statements will be added to thistest method when available.DIRT9. Apparatus9.1 Si
19、eveA45-m (No. 325) sieve conforming to Specifi-cation E11.10. Reagents10.1 Petroleum, Light, boiling between 60 and 80C.10.2 Rubber Peptizing Agent.NOTE 1The peptizing agent selection is not critical but, where one isused that contains inert mineral filler, the peptizer should be added to therubber
20、solvent and filtered5prior to addition of the rubber.10.3 Rubber Solvent, Xylene, or a Hydrocarbon Solvent,with a distillation range within 135 to 220C.11. Procedure11.1 Weigh a 10 to 12-g specimen of homogenized rubber tothe nearest 0.1 g and cut into pieces having a maximumdimension of less than 3
21、 mm. Place the pieces in a 250-cm3conical flask and cover with 150 cm3of rubber solventcontaining about 0.5 g of peptizing agent. Heat the mixture andmaintain it at a temperature of 125 to 130C (Note 2) untildissolution is complete (about 3 h).NOTE 2Overheating or boiling may cause gelling or charri
22、ng. Infra-red heating lamps and magnetic stirring are aids that will induce rubbersolution.11.2 Pour the hot solution through a 45-m (No. 325) sievepreviously weighed to the nearest 0.1 mg. Rinse the flask threetimes with about 25 cm3of hot rubber solvent and pour therinsings through the sieve. Tran
23、sfer any dirt remaining in theflask to the sieve by means of a jet of light petroleum and washthe dirt on the sieve until free of rubber solution. Dry the sieveand contents at 100 6 5C and weigh to the nearest 0.1 mg.12. Calculation12.1 Calculate the dirt content as follows:D 5 C 2 B!/A 3 100 (2)whe
24、re:D = percentage of dirt,A = mass of the specimen,B = mass of the clean, dry sieve, andC = mass of the sieve plus dirt.13. Precision and Bias13.1 Task groups for the purpose of obtaining precision andbias data in accordance with Practice D4483 are being orga-nized and precision and bias statements
25、will be added to thistest method when available.ASH14. Apparatus14.1 CrucibleAn unetched porcelain crucible having acapacity of 50 cm3. If copper is subsequently to be determined,a smooth unetched silica crucible is preferred, but a Vycorcrucible or an ignited, acid-washed unetched No. 2 Coorsporcel
26、ain crucible may be used.NOTE 3In cases of dispute where the greatest accuracy is required,use a new, smooth silica crucible each time the test is run.14.2 Muffle Furnace, with temperature indicator and con-trol.14.3 Filter Paper, Ashless, about 150 mm in diameter.15. Procedure15.1 Weigha5to6-gspeci
27、men of homogenized rubber tothe nearest 1 mg and place it in a crucible previously ignitedand weighed to the nearest 0.1 mg. Place the crucible and itscontents in a furnace controlled at a temperature of 550 6 25Cuntil free from carbon (Note 4). When ashing is complete, coolthe crucible in a desicca
28、tor and then weigh it to the nearest 0.1mg.NOTE 4The rubber may be charred over a small flame or on a hotplate before it is placed in the furnace. When the rubber is not previouslycharred before placing it in the furnace, the crucibles shall be placed on asuitable tray to permit placing them in the
29、furnace simultaneously, and thedoor of the furnace shall then be kept closed for at least 1 h whileflammable vapors are evolved. If copper, manganese, or iron is to bedetermined, the specimen shall be wrapped in a 150-mm ashless filterpaper previous to ashing.5The sole source of supply of the appara
30、tus (Number 40 Watman filter paper)known to the committee at this time is Fischer Scientific, 1600 W. Glenlake Ave.,Itasca, IL 60143. If you are aware of alternative suppliers, please provide thisinformation to ASTM International Headquarters. Your comments will receivecareful consideration at a mee
31、ting of the responsible technical committee,1whichyou may attend.D1278 91a (2011)216. Calculation16.1 Calculate the ash content as follows:A 5 C 2 B!/D 3 100 (3)where:A = percentage of ash,D = mass of the specimen,B = mass of the empty crucible, andC = mass of the crucible plus ash.17. Precision and
32、 Bias17.1 Task groups for the purpose of obtaining precision andbias data in accordance with Practice D4483 are being orga-nized and precision and bias statements will be added to thistest method when available.COPPER(Referee Colorimetric Method)618. Apparatus18.1 PhotometerA spectrophotometer or a
33、photoelectricphotometer with a band pass filter having maximum transmit-tance at about 435 nm. Matched absorption cells, 1 to 5 cm inpath length may be used, however, cells 2 to 5 cm in pathlength are preferred.NOTE 5For definitions of terms used in this procedure, refer toTerminology E131. The cm u
34、nit is not a preferred submultiple of the metrebut it is used by Committee E13 on Molecular Microscopy. (SeeTerminology E131).19. Reagents and Materials19.1 Carbon Tetrachloride (CCl4).19.2 Copper Sulfate, Standard Solution (1 cm3= 0.1 mgCu)Dissolve 0.393 g of copper sulfate (CuSO45H2O) inwater, add
35、 3 cm3of concentrated sulfuric acid (H2SO4,density = 1.84 Mg/m3), and dilute to 1 cm3with water. Thissolution should remain stable for at least a month.19.3 Copper Sulfate, Standard Solution (1 cm3= 0.01 mgCu)Dilute 10 cm3of the CuSO4solution (1 cm3= 0.1 mgCu) to 100 cm3with water. Make up this solu
36、tion fresh eachday.19.4 Nitric Acid (1 + 2)Mix 1 volume of concentratednitric (HNO3, density = 1.42 Mg/m3) with 2 volumes of water.19.5 Zinc Dibenzyldithiocarbamate Solution7Dissolve0.1 g of zinc dibenzyldithiocarbamate in 1 cm3of CCl4.NOTE 6The commercial grade of zinc dibenzyldithiocarbamate7isusu
37、ally suitable for use as a reagent. Lower blanks and more rapidextractions, however, may be obtained with the purified reagent.Amethodof preparation of pure reagent is available in the literature.620. Preparation of Calibration Curve20.1 Pipet 0, 1, 2, 3, and 4-cm3separate portions of standardCuSO4s
38、olution (1 cm3= 0.01 mg Cu) into separate separatoryfunnels. Add 5 cm3of HNO3(19.4) to each funnel and diluteto about 100 cm3. With a pipet add 25 cm3of zinc dibenzyl-dithiocarbamate solution to each funnel if 2 to 5-cm absorptioncells are to be used, or 10 cm3of the solution if 1-cm cells areto be
39、used.20.2 Proceed with the extraction as described in 21.1 andmeasure the absorbance of the CCl4solution as described in21.1, using the solution with no added copper as the referencesolution.20.3 Prepare a calibration curve by plotting the relationshipbetween copper concentration and absorbance. The
40、 calibrationcurve should be checked whenever necessary, depending onlocal conditions and on the type of instrument used.21. Procedure21.1 Ash a 10-g specimen wrapped in filter paper inaccordance with Section 15. Ash a blank consisting of the filterpaper in the same manner and carry it through the pr
41、ocedure inthe same manner as the specimen. Add 10 cm3of HNO3(19.4)to the crucible and digest the mixture on a steam bath for 30min. Transfer the solution to a 100-cm3volumetric flask. Cooland dilute it to the 100-cm3mark with water. Pipet 50 cm3ofthe solution into a separatory funnel and dilute to a
42、bout 100cm3with water. With a pipet add 25 cm3of zinc dibenzyldi-thiocarbamate solution if 2 to 5-cm absorption cells are to beused or add 10 cm3of the solution if the 1-cm cells are to beused. Shake the mixture vigorously for 1 min, allow the layersto separate, and draw off the CCl4layer through a
43、funnelcontaining a plug of absorbent cotton, directly into the absorp-tion cell. Leave a small amount of CCl4in the separatoryfunnel so as to avoid introducing water into the cell. If thereagents are sufficiently pure, this one extraction is sufficient.Each new reagent solution shall be tested. If a
44、 second succes-sive extraction removes additional copper, it will be necessaryto make additional extractions and combine the extracts. In thiscase combine the extracts in a 50-cm3volumetric flask anddilute with the reagent to the 50-cm3mark.21.2 Measure the absorbance with a spectrophotometer at435
45、nm or, if a photoelectric photometer is used, by using theappropriate filter. Use the blank solution as the referencesolution. Determine the concentration of copper in the testsolution from the absorbance reading and the calibration curve(20.3). Express the result in milligrams of copper per kilogra
46、mof rubber (parts per million).22. Precision and Bias22.1 Task groups for the purpose of obtaining precision andbias data in accordance with Practice D4483 are being orga-nized and precision and bias statements will be added to thistest method when available.COPPER(Alternative Colorimetric Method)23
47、. Apparatus23.1 See Section 18 and Note 4.6Martens, R. I., and Githens, Sr., R. E., “Small Amounts of Copper in Dyes andRubber Chemicals,” Analytical Chemistry , Vol 24, 1952, pp. 9913. Reprinted inRubber Chemistry and Technology, Vol 26, 1953, pp. 257262.7The sole source of supply of this salt (tra
48、de name Arazate) known to thecommittee at this time is Uniroyal Chemical, Elm Street, Naugatuck, CT 06770. Ifyou are aware of alternative suppliers, please provide this information to ASTMInternational Headquarters. Your comments will receive careful consideration at ameeting of the responsible tech
49、nical committee,1which you may attend.D1278 91a (2011)324. Reagents and Materials24.1 Ammonium Hydroxide (density = 0.90 Mg/m3)Concentrated ammonium hydroxide (NH4OH).24.2 Chloroform (CHCl3).24.3 Citric Acid Solution (33.33 %)Dissolve 50 g of citricacid in 100 cm3of water.24.4 Copper Sulfate, Standard Solution (1 cm3= 0.1 mgCu)See 19.2.24.5 Copper Sulfate, Standard Solution (1 cm3= 0.01 mgCu)See 19.3.24.6 Hydrochloric Acid-Nitric Acid MixtureMix 2 vol-umes of concentrated hydrochloric acid (HCl, density = 1.19Mg/m3) with 1 volume of co
