1、Designation: F3203 16F3203 18Standard Test Method forDetermination of Gel Content of Crosslinked Polyethylene(PEX) Pipes and Tubing1This standard is issued under the fixed designation F3203; the number immediately following the designation indicates the year oforiginal adoption or, in the case of re
2、vision, the 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. Scope Scope*1.1 The gel content of pipe and tubing produced from crosslinked polyethylene plastics as descr
3、ibed in Specification F876 andother pipe or tubing standards is determined by extracting with solvents such as xylenes. A test method for quantitativedetermination of gel content is described herein. The method is applicable to PEX pipe and tubing of all densities, including thosecontaining fillers,
4、 and provides correction for the inert fillers present in some of those compounds.1.2 Continuous extraction (see definition in Section 3) is used in this method to test the gel content of crosslinked polyethylenespecimens. Continuous extraction when used for testing gel content has the advantages of
5、 decreased the cost of testing, increasedaccuracy and consistency of results, and decreased test time. This is because extraction with a pure solvent is more efficient thanextraction with a partially saturated solvent.1.3 While extraction tests may be made on articles of any shape, this test method
6、is applicable for determining the gel contentof crosslinked polyethylene pipes and tubing.1.4 This test method makes use of xylenes or alternative solvents which have lower toxicity than xylenes. The alternativesolvents are also potentially beneficial from an economic and environmental viewpoint. Xy
7、lenes are used for referee tests.1.5 The values stated in SI units are to be regarded as standard. The inch-pound units in brackets are for information onlyonly.1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibilityof the u
8、ser of this standard to establish appropriate safety safety, health, and healthenvironmental practices and determine theapplicability of regulatory limitations prior to use.1.7 This international standard was developed in accordance with internationally recognized principles on standardizationestabl
9、ished in the Decision on Principles for the Development of International Standards, Guides and Recommendations issuedby the World Trade Organization Technical Barriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2D883 Terminology Relating to PlasticsD1603 Test Method for Carbo
10、n Black Content in Olefin PlasticsD2765 Test Methods for Determination of Gel Content and Swell Ratio of Crosslinked Ethylene PlasticsD7567 Test Method for Determining Gel Content in Crosslinked Ethylene Plastics Using Pressurized Liquid Extraction(Withdrawn 2015)3E177 Practice for Use of the Terms
11、Precision and Bias in ASTM Test MethodsE691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test MethodF876 Specification for Crosslinked Polyethylene (PEX) Tubing2.2 ISO Standard:4ISO 10147 Pipes and Fittings Made of Crosslinked Polyethylene (Pe-X) Estimation of the
12、 Degree of Crosslinking byDetermination of the Gel Content1 This test method is under the jurisdiction of ASTM Committee F17 on Plastic Piping Systems and is the direct responsibility of Subcommittee F17.40 on Test Methods.Current edition approved Aug. 1, 2016Aug. 1, 2018. Published September 2016Se
13、ptember 2018. Originally approved in 2016. Last previous edition approved in 2016 asF320216. DOI: 10.1520/F32031610.1520/F3203182 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information
14、, refer to the standards Document Summary page on the ASTM website.3 The last approved version of this historical standard is referenced on www.astm.org.4 Available from International Organization for Standardization (ISO), ISO Central Secretariat, BIBC II, Chemin de Blandonnet 8, CP 401, 1214 Verni
15、er, Geneva,Switzerland, http:/www.iso.org.This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Becauseit may not be technically possible to adequately depict all changes accurately, AS
16、TM recommends that users consult prior editions as appropriate. In all cases only the current versionof the standard as published by ASTM is to be considered the official document.*A Summary of Changes section appears at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO
17、 Box C700, West Conshohocken, PA 19428-2959. United States13. Terminology3.1 Terms as shown in Terminology D883 are applicable to this test method.3.2 Definitions of Terms Specific to This Standard:3.2.1 continuous extractor, ntest apparatus for performing a continuous extraction.3.2.1.1 DiscussionS
18、oxhlet, Knofler-Bohm, and Kumagawa extractors are examples of continuous extractors. A continuous extractor has three maincomponents which are a boiling flask or vessel for the solvent, a condenser, and a siphon cup. There are various designs for thesiphon cup; the Soxhlet, Knofler-Bohm, and Kumagaw
19、a designs are the most common.3.2.2 continuous extraction, nan extraction performed in a continuous extractor where a solvent (normally xylenes) is heatedin a vessel and boils forming vapors, the vapors rise and condense on a condenser to form droplets, the droplets fall into a cupwhere one or more
20、specimens are placed, there the solvent in the tray dissolves some of the un-crosslinked polyethylene in thespecimens, and when the cup holding the specimens is filled with solvent, the solvent now containing some of the un-crosslinkedpolyethylene drains out through a siphon tube back into the vesse
21、l where it started. The solvent and the sample specimens in thecup are kept warm by solvent vapor rising toward the condenser. The extraction steps repeat automatically and continuously aslong as heat is applied to the vessel holding the solvent. Because only the solvent evaporates and not the mater
22、ial dissolved in it,the concentration of un-crosslinked polyethylene in the boiling solvent increases, while the concentration of un-crosslinkedpolyethylene in the specimens continually decreases.3.2.3 gel content, nthe percentage by mass of polymer insoluble in a specified solvent after extraction
23、under the specifiedconditions.4. Summary of Test Method4.1 Specimens of the crosslinked ethylene plastic are prepared, weighed and then extracted using a heated extraction solventin a continuous extractor for the time designated by the procedure. After extraction, the specimens are removed from thec
24、ontinuous extractor, dried, and weighed as directed. The gel content is calculated using the final and initial specimen weights asdirected in the calculations section of this test method.5. Significance and Use5.1 Many important properties of crosslinked ethylene plastics vary with the gel content.
25、Hence, determination of the gel contentprovides a basis for controlling production processes and a means of establishing the quality of finished products.5.2 Extraction tests permit verification of the proper gel content of any given crosslinked ethylene plastic and they also permitcomparison betwee
26、n different crosslinked ethylene plastics, including those containing fillers, provided that, for the latter, thefollowing conditions are met:5.2.1 The filler is not soluble in the solvent used in this method at the extraction temperature.5.2.2 The amount of filler present in the compound either is
27、known or can be determined.5.2.3 Sufficient crosslinking has been achieved to prevent migration of filler during the extraction. It has been found that, at gelcontent above 30 %, the solvent remains clear and free of filler.5.3 Since some oxidative degradation of the material and solvent may occur a
28、t the reflux temperature of the solvents, a suitableantioxidant is added to the solvent to inhibit such degradation.5.4 This test method is normally used for specimens consisting of an equal representation of the entire cross section of theproduct, but may also be used to examine specific portions o
29、f a product for differences in extent of cross-linking when comparedto either a product standard or another sample.5.5 This test method is intended for testing crosslinked polyethylene compounds that are not hygroscopic. If compounds thatare hygroscopic are tested using this method, specimen conditi
30、oning before and after extraction is required.5.6 This standard differs from test methods Test Methods D2765, and Test Method D7567 which also describe procedures fordetermining the gel content of crosslinked polyethylene. It allows for the use of naphthenic blend or isoparaffin solvent as analterna
31、tive to xylenes. Xylenes are the only solvent allowed to be used for referee tests.The preferred method of sample preparationin this standard is to use a lathe to create thin ribbons of PEX material. This standard requires the use of a continuous extractorin order to provide consistent results and t
32、o allow for reliable solvent re-use. Specialized specimen holders are used to minimizevariability resulting from loss of specimen particles.NOTE 1Pressurized extraction techniques have been found to yield useful results in a shorter time frame, however not all grades of PEX tolerate theelevated extr
33、action temperatures without substantial degradation. For this reason pressurized extraction techniques are recommended for control tests onlyif it is possible to determine that the crosslinked matrix of the PEX does not break down at the temperature of extractionF3203 1826. Conditioning6.1 Condition
34、ingConditioning of the test specimens is not required, unless specified by the manufacturer of the material beingsampled.6.2 Test ConditionsTest conditions do not affect results, with the exception of atmospheric pressure. Conduct tests in alaboratory with atmospheric pressure greater than 80 kPa (l
35、ess than 6000 ft above average sea level).NOTE 2The altitude above sea level of the lab will influence the atmospheric pressure, which in turn will affect the boiling temperature of the solventused and the rate at which it will be able to extract un-crosslinked polyethylene from the matrix.7. Appara
36、tus7.1 Continuous Extractor, of the following general type, as illustrated in Fig. 1. Further information regarding possible sourcesof components is included in the Appendix X3.7.1.1 Boiling Flask, with a ground-glass joint. The flask may be either flat bottom or round bottom. For one or twodetermin
37、ations at a time, the minimum appropriate size is 500- mL. For routine testing with several determinations at one time,but not exceeding six, a 2000-mL flask is suitable.7.1.2 Heating Mantle or Hot Plate, to fit the flask and with sufficient heating capacity to boil the solvent used. If a flat botto
38、mflask is used a hotplate shall be used instead of a heating mantle, and shall have sufficient heating capacity to boil the solvent used.7.1.3 Extractor Cup, with a ground-glass joint to fit the boiling flask, a large mouth ground-glass joint on the top and sufficientcapacity to hold specimen cages
39、as described in 7.3.2. The extractor cup shall be of a jacketed design so that the specimens areFIG. 1 Continuous ExtractorF3203 183extracted at as near as possible to the boiling temperature of the solvent. The extractor cup and the boiling flask must be of matedcapacity, as the boiling flask must
40、have sufficient solvent in to safely be used as the extractor cup fills and drains. The extractorcup will be described with different names by laboratory glassware suppliers. These names include modified Soxhlet extractor,jacketed Soxhlet extractor, and Knofler-Bohm extractor. Review appendix X3.3 f
41、or supplier information.7.1.4 Reflux Condenser, with ground-glass joint to fit into the extractor cup. This will typically be an Allihn or Dimrothcondenser.7.1.5 Ring Stand and Appropriate Clamps7.2 Lathe, Drill Press, Plane or Planer, suitable for reducing the sample to a thickness of 0.15 to 0.05
42、mm. A bench top latheis preferred, although any procedure which will produce a sample of the required fineness without generating excessive heat isacceptable. Appendix X2 presents examples of devices suitable for sample preparation.7.3 Specimen Holders or Cages:7.3.1 Specimen Holders, of the general
43、 type illustrated in Fig. 2, machined aluminum with an internal volume of 6 to 7 cm3.The recommended design consists of two end caps and a spacer ring. The end caps shall be held together either by rare earth(samarium cobalt) magnets or a threaded connection to the spacer ring. The end caps shall ha
44、ve US No. 150 stainless steel wiremesh nested inside of the openings. The wire mesh is held between the spacer ring and the end caps to prevent specimen particlesfrom escaping when the specimen holder is closed. The exposed surface area of the wire mesh in the end caps shall be a minimumof 11 cm2. I
45、ndividual specimen holders are identified by an engraved number or letter on the end caps. Specimen holders arereusable. Construction drawings for suitable specimen holders are available in Appendix X1.7.3.2 Specimen Cages, made from U.S. No 150 stainless steel wire cloth. Prepare specimen cages by
46、cutting pieces of stainlesssteel wire cloth measuring 80 by 50 mm (3 by 2 in.). Fold these in half to form rectangles measuring approximately 40 by 50 mm(1 12 by 2 in.) Fold two sides of these rectangles closed by folding at the edges about 6 to 7 mm (14 in.). In this manner, cagesopen at the top is
47、 obtained. Specimen cages may be reused several times provided that they are completely free of any polymerresidue and do not have holes in them that would allow specimen particles to escape.7.4 Oven, capable of heating specimen holders to 150C (300F)150 C (300 F) with temperature indication. This o
48、ven shallbe of such construction and design to maximize air circulation. Convection toaster ovens sold for kitchen use have been found tobe adequate provided they are used in a fume hood. Alternatively a vacuum oven may be used.7.5 Analytical Balance, , minimum capacity of 100 g and capable of weigh
49、ing to 6 0.0001 g.7.6 Wood Block, Wood Block, 62 mm (212 in.) by 37 mm (112 in.) by 37 mm (112 in.).7.7 Timer, capable of timing intervals up to 10 hours, accurate to 6 30 s per hour or better, and with an audible alarm at thecompletion of the timed interval.FIG. 2 Specimen HolderF3203 1848. Reagents8.1 Extraction solvent, xylenes are the preferred solvent and must be used for referee tests; however any one of the followingsolvents may be used for control tests:8.1.1 Naphthenic hydrocarbon blend, boiling range 113 to 145C.145 C. See Appendix X4.8.1.2 Is
