1、Designation: D 2765 01 (Reapproved 2006)Standard Test Methods forDetermination of Gel Content and Swell Ratio ofCrosslinked Ethylene Plastics1This standard is issued under the fixed designation D 2765; the number immediately following the designation indicates the year oforiginal adoption or, in the
2、 case of revision, 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. Scope*1.1 The gel content (insoluble fraction) produced in ethyl-ene plastics by crosslinking c
3、an be determined by extractingwith solvents such as decahydronaphthalene or xylenes. Suchextraction test methods are described herein. They are appli-cable to crosslinked ethylene plastics of all densities, includingthose containing fillers, and all provide corrections for the inertfillers present i
4、n some of those compounds.1.2 Test MethodA, which permits most complete extractionin least time, is to be used for referee tests, but two alternativenonreferee Test Methods B and C are also described. The firstof these differs from the referee test method only in samplepreparation; that is, it requi
5、res use of shavings taken at selectedpoints in cable insulation, for example, rather than the groundsample required by the referee test method. Because the shavedparticles are larger, less total surface per sample is exposed tothe extractant, so this test method ordinarily yields extractionvalues ab
6、out 1 to 2 % lower than the referee method. Thesecond of the alternative test methods requires that a specimenin one piece be extracted in xylenes at a constant temperatureof 110C. At this temperature and with a one-piece specimen,even less extraction occurs (from 3 to 9 % less than the refereetest
7、method) but swell ratio (a measure of the degree ofcrosslinking in the gel phase) can be determined.1.3 Extraction tests can be made on articles of any shape.They have been particularly useful for electrical insulationssince specimens may be selected from those portions of theinsulation most suscept
8、ible to insufficient crosslinking.1.4 The values stated in SI units are to be regarded asstandard. The inch-pound units in brackets are for informationonly.NOTE 1ISO 10147 is similar to this test, but is not equivalent.1.5 This standard does not purport to address all of thesafety concerns, if any,
9、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. Specific precau-tionary statements are given in Sections 6, 10, and 25.2. Referenced Documents2
10、.1 ASTM Standards:2D 297 Test Methods for Rubber ProductsChemicalAnalysisD 618 Practice for Conditioning Plastics for TestingD 883 Terminology Relating to PlasticsD 1603 Test Method for Carbon Black Content in OlefinPlasticsD 1998 Specification for Polyethylene Upright StorageTanksD 3351 Test Method
11、 for Gel Count of Plastic Film3E 691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method3. Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 gel contentthe percentage by mass of polymerinsoluble in a specified solvent after extraction under t
12、hespecified conditions.3.1.2 solublecapable of being loosened or dissolved, sus-ceptible of being dissolved in or as if in a fluid. (See WebstersNinth New Collegiate Dictionary, 1988.)3.1.3 swell ratiothe ratio of the gel volume in the swollenstate to its volume in the unswollen state.3.2 Terms as s
13、hown in Terminology D 883 are applicable tothis test method.4. Summary of Test Methods4.1 Specimens of the crosslinked ethylene plastic areweighed and then immersed in the extracting solvent at thetemperature specified by the procedure selected and for thetime designated by that procedure. After ext
14、raction, the speci-mens are removed, dried, and reweighed as directed. Theamount of material extracted is calculated and, if desired, swell1These test methods are under the jurisdiction of ASTM Committee D20 onPlastics and are the direct responsibility of Subcommittee D20.15 on ThermoplasticMaterial
15、s.Current edition approved April 1, 2006. Published April 2006. Originallyapproved in 1968. Last previous edition approved in 2001 as D 2765 01.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards v
16、olume information, refer to the standards Document Summary page onthe ASTM website.3Withdrawn.1*A Summary of Changes section appears at the end of this standard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.ratio also may be determi
17、ned by the means described inalternative Test Method C.5. Significance and Use5.1 Many important properties of crosslinked ethylene plas-tics vary with the gel content. Hence, determination of the gelcontent provides a means of both controlling the process andrating the quality of finished products.
18、5.2 Extraction tests permit verification of the proper gelcontent of any given crosslinked ethylene plastic and they alsopermit comparison between different crosslinked ethyleneplastics, including those containing fillers, provided that, forthe latter, the following conditions are met:5.2.1 The fill
19、er is not soluble in either decahydronaphtha-lene or xylenes at the extraction temperature.5.2.2 The amount of filler present in the compound either isknown or can be determined.5.2.3 Sufficient crosslinking has been achieved to preventmigration of filler during the extraction. Usually it has beenfo
20、und that, at extraction levels up to 50 %, the extractantremains clear and free of filler.5.3 Since some oxidative degradation of the material canoccur at the reflux temperature of the extractants, a suitableantioxidant is added to the extractant to inhibit such degrada-tion.5.4 Before proceeding wi
21、th this test method, referenceshould be made to the specification of the material being tested.Any test specimen preparation, conditioning, dimensions, ortesting parameters, or a combination thereof, covered in thematerials specification shall take precedence over those men-tioned in this test metho
22、d. If there are no material specifica-tions, then the default conditions apply.6. Precautions6.1 This test method measures a much larger three dimensional polymer network than that measured by TestMethod D 3351 and should not be confused with it.6.2 It has been reported that crosslinked ultra-high m
23、olecu-lar weight polyethylene fails to completely dissolve in thisprocedure at times.7. Conditioning7.1 ConditioningCondition the test specimens at 23 62C 73.4 6 3.6F for not less than 40 h prior to test inaccordance with Procedure A of Practice D 618, for those testswhere conditioning is required.
24、In cases of disagreement, thetolerance shall be 6 1C 61.8F.7.2 Test ConditionsPrepare samples in the standard labo-ratory atmosphere of 23 6 2C 73.4 6 3.6F, unlessotherwise specified in the test methods. In cases of disagree-ment, the tolerance shall be 61C 61.8F.TEST METHOD A (REFEREE TEST METHOD)8
25、. Apparatus8.1 The extraction apparatus shall be of the followinggeneral type, as illustrated in Fig. 1:8.1.1 Round-Bottom Flask, with large-mouth ground-glassor cork joint. For one or two determinations at one time, a500-mL flask is appropriate. For several determinations at onetime, but not exceed
26、ing six, a 2000-mL flask is suitable.8.1.2 Heating Mantle to fit the flask and with sufficientheating capacity to boil decahydronaphthalene (boiling point190 to 193C) or xylenes (boiling point 138 to 141C).8.1.3 Reflux Condenser with ground-glass or cork joint tofit into flask.8.1.4 Ring Stand and A
27、ppropriate Clamps.8.2 Grinding Equipment, suitable for reducing the sample toa fineness between 30 and 60 mesh. A bench-top laboratorymill4,5is satisfactory, although any procedure which willproduce a sample of the required fineness without generatingexcessive heat may be used.8.2.1 U.S. No. 30 and
28、U.S. No. 60 Sieves.8.2.2 U.S. No. 120 Stainless Steel Wire Cloth.8.3 Vacuum Oven, with vacuum source capable of creatinga vacuum of at least 710 mm 28 in. Hg and equipped with athermometer capable of measuring 150C.8.4 Analytical Balance, capable of weighing to 0.001 g.NOTE 2If a slightly higher deg
29、ree of accuracy is desired (about 1 to2 %) a modified Soxhlet Extractor; Kontes Catalog No. 586100-0023,Size C, Kontes Glass Co., Vineland, NJ or equivalent may be employedwherein the specimen is held in an extraction thimble. The extractionthimble, with extra-coarse fritted glass disk sealed in; Ko
30、ntes 586500-0023, 45-mm body diameter, 130-mm height or equivalent (height mustsubsequently be cut to 75 mm). The fritted disk is extra-coarse with fusededge; Kontes 952000-4025, 40-mm diameter or equivalent. Glass wool 13to 19 mm thick 12 to34 in. placed on the bottom of the extraction thimbleto su
31、pport one gram 3060 mesh ground sample which is covered with 13to 19 mm thick layer of glass wool, a fritted glass disk and a small glassweight. The extraction thimble assembly rests upon the 55-mm portion ofthe thimble previously cut off, the latter inserted into the modified Soxhlet.9. Reagents9.1
32、 Decahydronaphthalene, anhydrous, boiling point 189 to191C.9.2 Xylenes,ACS reagent grade, boiling point 138 to 141C.9.3 2,28-methylene-bis (4-methyl-6-tertiary butyl phenol)5,610. Safety Precautions10.1 Xylenes and decahydronaphthalene are toxic and flam-mable solvents and as such should be handled
33、carefully. Useonly in a ventilated hood. Check the effectiveness of the hoodbefore starting the tests. Do not inhale the vapors. Excessiveinhalation of the vapors may cause dizziness or headache, orboth. In the event of excessive inhalation, seek fresh clean air.11. Test Specimens11.1 At least two s
34、pecimens each containing 0.300 6 0.015g of ground polymer weighed to the nearest 0.001 g shall betested.4A Wiley Cutting Mill, Intermediate Model, or equivalent, Catalog No. 08-338,available from Fisher Scientific Co., 711 Forbes Ave., Pittsburgh, PA 15219, hasbeen found satisfactory for this purpos
35、e.5If 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.6Antioxidant, available from Cytec under the trade name Cyanox
36、2246, has beenfound satisfactory for this purpose. Cytec Industries, PolymerAdditive Department,5 Garret Mountain Plaza, West Paterson, NJ 07424.D 2765 01 (2006)211.2 The test samples shall be ground to a fineness that willpass through a 30-mesh sieve. Shake this sieved material overa 60-mesh sieve
37、and reject any material that passes through.11.3 Test specimens originating from insulation cut fromwire should be homogeneous and consist of an equal mixtureof samples representative of insulation nearest to the conductorand samples representative of insulation nearest the outerperiphery of the con
38、struction unless specific portions of theinsulation are being examined for insufficient crosslinking.12. Procedure12.1 Prepare a specimen holder by cutting a piece of120-mesh stainless steel cloth measuring approximately 80 by40 mm 3 by 112 in. Fold this to form a square measuringapproximately 40 mm
39、 112 in. Fold two sides of this squareclosed by folding the cloth at the edges about 6 to 7 mm 14 in.and stapling those folds. In that manner, a pouch open at thetop is obtained. Weigh this pouch (W1).12.2 Place approximately 0.3 g of the ground and screenedsample in the weighed pouch. Weigh the pou
40、ch and specimen(W2). Fold over the open side of the pouch and staple the edgeto form a cage. Weigh the cage and sample (W3).12.3 Fill a round-bottom flask as described in 8.1.1 withenough solvent to immerse the 120-mesh cage and samplecompletely. Three hundred fifty grams in a 500-mL flask or1000 g
41、in a 2000-mL flask is sufficient. Dissolve 1 % ofantioxidant in the decahydronaphthalene or xylenes to inhibitfurther crosslinking of the specimen.12.4 Boil the decahydronaphthalene or xylenes vigorouslyenough to ensure good agitation of the solution. Twenty to 40drops/min from the condenser, while
42、using 1000 g of solvent,is a satisfactory boiling rate. Suspend the cage and specimen inthe solvent so that the bottom edge of the cage is almosttouching the bottom of the flask. A small wire, attached to thecage and extending through the reflux condenser can be usedfor suspending the cage. Extract
43、the specimen for6hindecahydronaphthalene or for 12 h in xylenes.NOTE 3Since most of the extraction occurs within less than thespecified time, the period of extraction may be shortened for control testson the basis of experience. If this is done, the time of extraction must bereported. For referee te
44、sts, extraction time is to be as specified by this testmethod.12.5 After extraction, place the cage and specimen imme-diately in a vacuum oven preheated to 150C. Dry theAIdentification tag and fine wire attached to cage.BReflux condenser.CRing stand clamp.DWater inlet.EGround-glass or cork joint.FLa
45、rge-mouth round-bottom flask.GVariable transformer.HWater outlet.IRing stand.JDecahydronaphthalene or xylene.KHeating mantle.L120-mesh wire cage containing the specimen.FIG. 1 Extraction ApparatusD 2765 01 (2006)3specimen to constant weight under at least 710 mm 28 in. Hgvacuum. Cool and weigh (W4).
46、 If the compound absorbsmoisture, cool the specimen in a desiccator before weighing.NOTE 4It has been reported that drying time sometimes can bematerially shortened if the cage and sample are cooled for 15 min and thenare placed either on a suspended screen or on lint-free absorbent materialto remov
47、e excess solvent before being put into the vacuum drying oven.12.6 If extraction tests are regularly made, the apparatusmay be left assembled and the extracting solvent (containinginhibitor as directed) may be reused until it darkens. However,if there is any doubt about the values obtained with reus
48、edextractant, the test should be repeated with fresh extractant.NOTE 5If the modified Soxhlet apparatus is used, the completethimble assembly containing1gofsample is weighed to the nearest60.0001 g before extraction and after vacuum drying.13. Calculation13.1 Calculate the solvent extraction in perc
49、ent as follows:Extract, % 5weight lost during extraction!/weight of original specimen 2 weight of filler! (1)5 W32 W4!/W22 W1! 2 FW22 W1!# 3 1005 W32 W4!/1 2 F! W22 W1!# 3 100where:W1= weight of the pouch (sealed on three sides, one sideopen),W2= weight of the specimen and the pouch (sealed onthree sides, one side open),W3= weight of the specimen and the cage, after beingstapled shut,W4= weight of the specimen and the cage after extractionand drying,F = fraction of filler (which must be insoluble in d
