ASTM_D_7723_-_11.pdf

Designation:D772311Standard Test Method forRubber PropertyMacro-Dispersion of Fillers inCompounds1This standard is issued under the fixed designation D7723;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 a procedure to measure themacro-dispersion of fillers in a rubber matrix by quantifyingthe surface roughness of a freshly cut specimen using anoptical microscope in reflection mode.1.2 The method provides a procedure to measure the qualityof mixing of reinforcing fillers such as silica and carbon black,as well as inert fillers such as chalk,clay and other solids.1.3 The method includes a sample preparation procedure forfilled uncured rubber compounds as well as filled cured rubbercompounds.1.4 The values stated in SI units are to be regarded asstandard.No other units of measurement are included in thisstandard.1.5 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:2D2663 Test Methods for Carbon BlackDispersion in Rub-berD3053 Terminology Relating to Carbon Black3.Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 agglomerates,nany number of filler aggregates heldtogether by van der Waals Forces(carbon black)or hydrogenbonding(silica).3.1.2 macro dispersion,ndegree of distribution of fillerinto a compound,generally on a scale of less than 100 m butgreater than 2 m;represents micron range agglomeration.3.1.3 nodges,nbumps in a cut surface caused by filleragglomerates in a rubber matrix.3.1.4 surface roughness,nthe bumps(nodges),or hillsand valleys that are on the visible side of a sample.3.1.5 white area,nthe portion of the scan area whichcontains nodges,or other surface defects;it is described here aswhite,because the reflected light from these surface defects iswhite.4.Summary of Test Method4.1 This standard uses mathematical algorithms to quantifythe surface roughness of freshly cut rubber specimens asmeasured by a reflected light optical method in two dimen-sions.4.2 The reflected light optical method,generally used todetermine a comparative dispersion rating,is expanded to givequantitative data as to the size and number of nodges.Nodgesdo not show the actual size of filler agglomerates.It is assumedthat as the sample is cut,large agglomerates are pushed to oneside or the other leaving a contoured surface.The diameter andfrequency of the surface contours are measured using imageprocessing.These contours are referred to as“nodges”todifferentiate them from actual agglomerates.This data ispresented in histogram form of count versus nodge diameter,and allows calculating a measure of dispersion.5.Significance and Use5.1 The incorporation of fillers into the rubber matrix ischaracterized by their macrodispersion as an indicator of thequality of mixing.This test method provides a measure of themacro-dispersion of reinforcing fillers,like silica and carbonblack,as well as of inert fillers.Based on their polymer nature,different types of rubbers can show a different degree ofacceptance for the incorporation of fillers,as indicated by theirmacro-dispersion.5.2 Macro-dispersion of carbon black and silica in rubbercompounds may be measured by different methods.Carbonblack provides a direct physical reinforcement;silica requires1This test method is under the jurisdiction of ASTM Committee D11 on Rubberand is the direct responsibility of Subcommittee D11.12 on Processability Tests.Current edition approved May 1,2011.Published July 2011.DOI:10.1520/D7723-11.2For 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.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 a silane coupling agent in order to initiate reinforcement,andtherefore,a different technology of mixing.Silica is also anon-conductor,making electrical methods of dispersion mea-surement impracticable.This test method is specifically appro-priate for the characterization of the microdispersion in silicatechnology.5.3 This test method also can measure the mixing quality ofcolored rubbers.It uses variable exposure in order to be able toimage a wide range of colors.5.4 This test method is intended for use in research anddevelopment as well as in quality control of filler processabilityin rubber and may be used for both the evaluation of produc-tion processes or referee purposes