1、Designation: D 6814 02 (Reapproved 2008)Standard Test Method forDetermination of Percent Devulcanization of Crumb RubberBased on Crosslink Density1This standard is issued under the fixed designation D 6814; the number immediately following the designation indicates the year oforiginal adoption or, i
2、n the case of revision, 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. Scope1.1 This test method covers the procedure for determiningpercent devulcanization from
3、crosslink density measurementsof devulcanized rubber and control crumb rubber in thelaboratory. Percent devulcanization is a quantitative determi-nation.1.2 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.3 This standard does
4、not purport 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 Standa
5、rds:2D 297 Test Methods for Rubber ProductsChemicalAnalysis3. Terminology3.1 Definitions:3.1.1 rubber, nnatural or synthetic elastomer that hasbeen chemically crosslinked/vulcanized to enhance its usefulproperties.3.2 Definitions of Terms Specific to This Standard:3.2.1 devulcanization, na process o
6、f breaking downchemical crosslinks in cured rubber.4. Summary of Test Method4.1 The crumb rubber sample is extracted in hot acetone perTest Methods D 297 and dried at 70 6 2C in a forced-ventilating air oven for 16 6 1 h. The dried crumb rubber isswollen in a solvent (for examples of polymer-solvent
7、 pairing,seeAppendix X1) with reagent grade purity, selection based onrubber type, for 24 h at room temperature. The solvent isreplaced with fresh solvent three times during the swellingprocess. After swelling, the solvent is wiped quickly from thesurface of the swollen crumb rubber using a clean pa
8、per towel.Measure the weight of the swollen sample in a preweighted andtared weighing bottle with closure. Dry it at 70 6 2C in aforced-ventilating air oven for 16 6 1 h. Cool to roomtemperature in a desiccator and weigh. The density of the driedcrumb rubber sample is measured using methanol instead
9、 ofdistilled water as an immersion liquid because of good wetta-bility of methanol to rubber. Using the swelling ratio, polymerdensity, polymer-solvent interaction parameter, and the Flory-Rehner equation,3the crosslink density of the sample iscalculated. Percent devulcanization is calculated usingc
10、rosslinking density data of devulcanized crumb rubber and thecontrol.5. Significance and Use5.1 It is important for rubber compounders to know theextent of devulcanization a rubber might have undergoneduring recycling. It allows the compounder to determine ifmore curing agents are needed during mixi
11、ng of devulcanizedrubber when used either as partial replacement or stand alone.6. Apparatus6.1 Analytical Balance, precision 0.0001 g.6.2 Extraction Apparatus, glass conical flask, extractioncup, and condenser.6.3 Beaker,50mL.6.4 Oven, temperature controlled within 62C.6.5 Paper Towel.6.6 Weighing
12、Bottles with Caps.7. Reagents and Materials7.1 The following reagents are used:7.1.1 Acetone, USP grade,7.1.2 Toluene, ACS grade, and1This test method is under the jurisdiction of ASTM Committee D11 on Rubberand is the direct responsibility of Subcommittee D11.20 on Compounding Materialsand Procedur
13、es.Current edition approved July 1, 2008. Published September 2008. Originallyapproved in 2002. Last previous edition approved in 2002 as D 6814 021.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStanda
14、rds volume information, refer to the standards Document Summary page onthe ASTM website.3Flory, P. J., Principles of Polymer Chemistry, Cornell University Press, Ithaca,NY, 1953, Chap. 13 (Equation 38), p. 578.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 1
15、9428-2959, United States.7.1.3 Methanol, ACS grade.7.2 Purity of ReagentsReagent grade chemicals shall beused in all tests. Unless otherwise indicated, it is intended thatall reagents conform to the specifications of the Committee onAnalytical Reagents of the American Chemical Society wheresuch spec
16、ifications are available.4Other grades may be used,provided it is first ascertained that the reagent is of sufficientlyhigh purity to permit its use without lessening the accuracy ofthe determination.8. Procedure8.1 Weigh 10 6 0.5 g of crumb rubber.8.2 Extract the sample with hot acetone for 16 h us
17、ing theextraction apparatus per Test Methods D 297 to eliminate theacetone-solubles.8.3 Dry the solids in an oven for 16 6 1hat706 2C ina forced-ventilating air oven. Discard the acetone.8.4 Cool the sample to 23 6 2C.8.5 Pour 200 6 10 cm3of toluene onto the dried sample(different rubber based crumb
18、 rubber may need differentsolvent). See Appendix X1. Let the sample swell at roomtemperature for 72 h. Do not stir during the swelling process.Replace the solvent with fresh solvent every 24 h during theswelling period.8.6 Remove liquid from the swollen sample and “pat dry”quickly with a soft paper
19、towel to remove excess liquid.8.7 Weigh the sample in a closed, tared, weighing bottle andrecord the weight of the swollen sample.8.8 Remove the cap from the weighing bottle and put boththe cap and the swollen rubber into a 70 6 2C forced-ventilating air oven overnight.8.9 Remove the dried sample bo
20、ttle and cap from the oven,immediately recap the bottle and allow to cool at roomtemperature. Weigh the closed bottle and calculate the weightof dried sample.8.10 For density measurement, weigh 0.5 6 0.1 g of thedried crumb rubber sample up to 0.0001 g on a tared aluminumfoil for easy handling of sa
21、mple. Record the weight. Thedifference between this weight and tared weight of aluminumfoil is the weight of dry sample.8.11 Take out the sample from the balance with aluminumfoil. Wet the sample with several drops of methanol. Transferthe wet sample to the weighing pan of the balance that is tareda
22、nd immersed in methanol. Record the weight of the sample inmethanol.8.12 Calculate the density of dry crumb rubber using theequation that is given below.Density at 23 6 2C in g/cm35 0.7913 3 A/A 2 B! (1)where:A = weight of specimen measured in air, g,B = weight of specimen measured in methanol, g, a
23、nd0.7913 = density of methanol at 23 6 2C in g/cm3.9. Calculation of Crosslink Density (ne)9.1 The Flory-Rehner3equation is used for calculation ofcrosslinking density.ne52ln1 2 Vr! 1 Vr1x1Vr2#V1Vr1/32 Vr! /2#(2)where:ne= effective number of chains in a real network per unitvolume,Vr= volume fractio
24、n of polymer in a swollen network inequilibrium with pure solvent and is calculated as:Vr5Weight of dry rubber / density of dry rubberWeight of dry rubberDensity of dry rubber1Weight of solvent absorbed by sampleDensity of solvent(3)NOTE 1The difference between the weights of swollen and driedsample
25、 are calculated from Procedures 7 and 9.where:x1= polymer-solvent interaction parameter, see AppendixX1, andV1= molecular volume of solvent.10. Calculation of Percent Devulcanization10.1 See Eq 4.% Devulcanization 5F1 2SCrosslink density of devulcanized rubberCrosslink density of control crumb rubbe
26、rDG3 100 (4)where the control crumb rubber is the compound beforeduvulcanization.11. Precision and Bias11.1 Round-robin testing will be conducted and precisionand bias statements will be balloted for inclusion when testingis completed.12. Keywords12.1 devulcanization; rubber4Reagent Chemicals, Ameri
27、can Chemical Society Specifications, AmericanChemical Society, Washington, DC. For suggestions on the testing of reagents notlisted by the American Chemical Society, see Analar Standards for LaboratoryChemicals, BDH Ltd., Poole, Dorset, U.S., and the United States Pharmacopeia andNational Formulary,
28、 U.S. Pharmacopeial Convention, Inc. (USPC), Rockville, MD.D 6814 02 (2008)2APPENDIX(Nonmandatory Information)X1. EXAMPLE OF SOLVENT FOR SWELLING CRUMB RUBBERX1.1 Solvents for swelling crumb rubber are listed in TableX1.1.ASTM International takes no position respecting the validity of any patent rig
29、hts asserted in connection with any item mentionedin this standard. 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
30、 time by the responsible technical committee and must be reviewed every 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 wi
31、ll receive careful consideration at a meeting of theresponsible technical 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 AS
32、TM 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); o
33、r through the ASTM website(www.astm.org).TABLE X1.1 Example of Solvents for Swelling Crumb RubberAPolymer Solvent Interaction ParameterBCis-polyisoprene Toluene 0.391 (at 25C)Benzene 0.437 (at 25C)Polyisobutylene Toluene 0.557 (at 25C)Cyclohexane 0.436 (at 25C)Butadiene-styrene Benzene 0.442 (at 25C
34、)(7.15:28.5) Cyclohexane 0.489 (at 25C)Butadiene-acrylonitrile82:18 Benzene 0.390 (at 25C)70:30 Benzene 0.486 (at 25C)61:39 Benzene 0.564 (at 25C)ARodriguez, F., Principle of Polymer Systems, 2nd Ed., McGraw-Hill, New York,1982, Ch. 2.BFor calculation of other interaction parameters, refer to the same reference asFootnote A.D 6814 02 (2008)3
