ASTM_D_6814_-_02_2013.pdf

Designation:D681402(Reapproved 2013)Standard Test Method forDetermination of Percent Devulcanization of Crumb RubberBased on Crosslink Density1This standard is issued under the fixed designation D6814;the number immediately following the designation indicates the year oforiginal adoption or,in 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 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 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 Standards:2D297 Test Methods for Rubber ProductsChemical Analy-sis3.Terminology3.1 Definitions:3.1.1 rubber,nnatural or synthetic elastomer that has beenchemically crosslinked/vulcanized to enhance its useful prop-erties.3.2 Definitions of Terms Specific to This Standard:3.2.1 devulcanization,na process of breaking downchemical crosslinks in cured rubber.4.Summary of Test Method4.1 The crumb rubber sample is extracted in hot acetone perTest Methods D297 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 pairing,see Appendix 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 paper 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 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 using cross-linking 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 mixing 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,50 mL.6.4 Oven,temperature controlled within 62C.6.5 Paper Towel.6.6 Weighing Bottles with Caps.7.Reagents and Materials7.1 The following reagents are used:7.1.1 Acetone,USP grade,1This test method is under the jurisdiction of ASTM Committee D11 on Rubberand is the direct responsibility of Subcommittee D11.20 on Compounding Materialsand Procedures.Current edition approved Nov.1,2013.Published January 2014.Originallyapproved in 2002.Last previous edition approved in 2008 as D6814 02(2008).DOI:10.1520/D6814-02R13.2For referenced ASTM standards,visit the ASTM website,www.astm.org,orcontact ASTM Customer Service at serviceastm.org.For Annual Book of ASTMStandards 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.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 7.1.2 Toluene,ACS grade,and7.1.3 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 specifications 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 using theextraction apparatus per Test Methods D297 to eliminate theacetone-solubles.8.3 Dry the solids in an oven for 16 6 1 h at 70 6 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 tolue