1、Designation: D7723 17D7723 18Standard 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
2、 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 the macro-dispersion of fillers in a rubber matrix by quantifying the surfa
3、ceroughness of a freshly cut specimen using an optical microscope in reflection mode.1.2 The method provides a procedure to measure the quality of mixing of reinforcing fillers such as silica and carbon black, aswell as inert fillers such as chalk, clay and other solids.1.3 The method includes a sam
4、ple preparation procedure for filled uncured rubber compounds as well as filled cured rubbercompounds.1.4 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.1.5 This standard does not purport to address all of the safety concerns
5、, if any, associated with its use. It is the responsibilityof the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability ofregulatory limitations prior to use.1.6 This international standard was developed in accordance with internat
6、ionally recognized principles on standardizationestablished 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:2D2663 Test
7、 Methods for Carbon BlackDispersion in RubberD3053 Terminology Relating to Carbon Black3. Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 agglomerates, nany number of filler aggregates held together by van der Waals Forces (carbon black) or hydrogenbonding (silica).3.1.2 macro di
8、spersion, ndegree of distribution of filler into a compound, generally on a scale of less than 100 m but greaterthan 2 m; represents micron range agglomeration.3.1.3 nodges, nbumps in a cut surface caused by filler agglomerates in a rubber matrix.3.1.4 surface roughness, nthe bumps (nodges), or hill
9、s and valleys that are on the visible side of a sample.3.1.5 white area, nthe portion of the scan area which contains nodges, or other surface defects; it is described here as white,because the reflected light from these surface defects is white.4. Summary of Test Method4.1 This standard uses mathem
10、atical algorithms to quantify the surface roughness of freshly cut rubber specimens as measuredby a reflected light optical method in two dimensions.1 This test method is under the jurisdiction of ASTM Committee D11 on Rubber and Rubber-like Materials and is the direct responsibility of Subcommittee
11、 D11.12 onProcessability Tests.Current edition approved Dec. 1, 2017Nov. 1, 2018. Published January 2018November 2018. Originally approved in 2011. Last previous edition approved in 20112017as D7723 11.D7723 17. DOI: 10.1520/D7723-17.10.1520/D7723-18.2 For referencedASTM standards, visit theASTM web
12、site, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indicati
13、on of what changes have been made to the previous version. Becauseit may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current versionof the standard as published by ASTM is to be consi
14、dered the official document.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States14.2 The reflected light optical method, generally used to determine a comparative dispersion rating, is expanded to givequantitative data as to the size and n
15、umber of nodges. Nodges do not show the actual size of filler agglomerates. It is assumed thatas the sample is cut, large agglomerates are pushed to one side or the other leaving a contoured surface.The diameter and frequencyof the surface contours are measured using image processing. These contours
16、 are referred to as “nodges” to differentiate them fromactual agglomerates. This data is presented in histogram form of count versus nodge diameter, and allows calculating a measureof dispersion.5. Significance and Use5.1 The incorporation of fillers into the rubber matrix is characterized by their
17、macrodispersion as an indicator of the qualityof mixing. This test method provides a measure of the macro-dispersion of reinforcing fillers, like silica and carbon black, as wellas of inert fillers. Based on their polymer nature, different types of rubbers can show a different degree of acceptance f
18、or theincorporation of fillers, as indicated by their macro-dispersion.5.2 Macro-dispersion of carbon black and silica in rubber compounds may be measured by different methods. Carbon blackprovides a direct physical reinforcement; silica requires a silane coupling agent in order to initiate reinforc
19、ement, and therefore,a different technology of mixing. Silica is also a non-conductor, making electrical methods of dispersion measurementimpracticable. This test method is specifically appropriate for the characterization of the microdispersion in silica technology.5.3 This test method also can mea
20、sure the mixing quality of colored 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 and development as well as in quality control of filler processability inrubber and may be used for both the evaluation of pro
21、duction processes or referee purposes.6. Apparatus6.1 Razor Blade (recommended) or Sharp KnifeThe specimen may be prepared using a static cut as shown in Fig. 1 or cutwhile being bi-directionally elongated as shown in Fig. 2.6.2 Reflected Light Microscope, with the following specifications:6.2.1 Ima
22、ging power to resolve to 1 m, 3 m, or 10 m depending on the instrument used.6.2.2 Dark field illumination as shown in Fig. 3.6.3 The light microscope is to be equipped with an image sensor. The sensor used to capture the image is a common CCD(Charged Coupled Device) or CMOS (Complementary Metal Oxid
23、e Semiconductor) sensor. In the dark field mode, an apertureis lit at a 30 angle for analysis. The sensor picks up the reflection of bumps on the surface, nodges representing undispersed filler.Flat areas of the sample surface are dark.6.4 A scan is made by taking a digital gray-level image in the d
24、ark field mode of the microscope with 1 m, 3 m, or 10 mresolution.6.5 The image captured by the sensor shall be digitized and analyzed by the image processing software. The area of nodges isrepresented as “White Area.” The percent White Area, URF%, is the percentage of the white area representing th
25、e nodges to thetotal area of the image. Based on this area ratio, percent dispersion can be calculated.7. Calculation7.1 As the specimen is cut, the underlying agglomerates are pushed to one side or another resulting in hills and valleys on thecut surface. They represent agglomerates under the surfa
26、ce of the cut. The nodge diameter that is calculated from these images islarger than the underlying agglomerate. For simplification, nodge size is reported as Agglomerate Size and represented by ahistogram (Fig. 4).FIG. 1 Static CutD7723 1827.2 In order to stay within the 2-100 m range of macro-disp
27、ersion defined in Terminology D3053, it is necessary to disregardsmall nodges that are covering the smaller agglomerates by introducing a threshold. Two different values for the threshold maybe used: 5 m and 23 m. The threshold value cannot be selected below the resolution of the microscope as state
28、d in 6.2.1. Thefrequency of occurrence of nodges decreases with a higher level of dispersion. Dispersion, therefore, is calculated from the whitearea, which is determined from the radius and frequency of all nodges greater than the nodge threshold.7.3 Calculate the White Area, URF, as a ratio to the
29、 total scan area.7.4 Calculate the percent dispersion of fillers as follows:Dispersion %5100 2 100 3 URF!/L (1)Dispersion %510021003URF/L (1)where:URF = fraction of total scan area from undispersed filler measured in reflectionL = the filler volume fraction in the compound7.4.1 For maximum accuracy,
30、 the filler volume fraction can be calculated from the following expression, which also appearsin Test Methods D2663:L 5 compound density 3filler massfiller density 3compound mass (2)FIG. 2 Bi-Directional CutFIG. 3 Darkfield IlluminationD7723 1837.5 If the volume percentage of filler in the rubber c
31、ompound L is either not given or unknown, calculate the weighted percentdispersion or Z Value as follows:Z value5100 2 100 3 URF!/0.35 (3)Z value510021003URF/0.35 (3)NOTE 1The Z Value assumes a maximum of 35 % white area. Fixing the volume fraction at a maximum value of 0.35 allows the user to skip
32、thetime-consuming step of determining the volume fraction, which is not necessary for quality control of a specific compound.8. Test Specimen8.1 The test specimen is prepared from a vulcanized or unvulcanized sample of a filled rubber compound.Arazor blade cut shallbe made, so that two similar surfa
33、ces are exposed. The surfaces shall be bigger than 5 by 5 mm.8.1.1 When preparing the test specimen, it is recommended that a new razor blade be used for each cut. The abrasiveness ofthe rubber as well as contaminates from the rubber left on the blade may affect successive cuts.8.1.2 The thickness o
34、f the uncut specimen shall be 5 to 10 mm. Thicker specimens cause excessive drag between the razor bladeand rubber and may affect the quality of the cut.8.1.3 The specimen shall be cut in one continuous motion.8.2 For unvulcanized samples, porosity which is generated during the slab preparation proc
35、ess should be eliminated. This isaccomplished by pressing a hot sample while cooling. The cut is made by placing the unvulcanized sample in a sample preparationsystem, where it is pulled bi-directionally, while a razor cuts. This is not required, but also recommended for cured specimens. Theprocedur
36、es specified in 7.1 shall be followed for bi-directionally cut specimens.9. Procedure9.1 A specimen cut according to 8.1 or 8.2 shall be placed in front of the testing window within two minutes after cutting.9.2 Set the threshold to 5 m or 23 m, and adjust the exposure time of the camera if possible
37、 (50 ms is recommended).9.3 A minimum of three scans of different locations of the freshly cut surface shall be taken. Five scans of different locationsare recommended. Calculate the average values of the scans. The user does not need to make a fresh cut for each of the five scans.9.4 Apply the calc
38、ulations expressed in Section 7.10. Report10.1 Percent Dispersion ValuesReport measured dispersion ratings to the nearest 0.1 %.10.2 If the calculation of percent dispersion in 7.4 is used, report the L value used in the calculation. If the calculation of theZ value in 7.5 is used, report the use of
39、 the 0.35 Z factor in the calculation.10.3 Agglomerate SizeReport the agglomerate size as histogram in classes of a width of 3 m.10.4 Report the average agglomerate size. In instances where a bimodal agglomerate distribution exists, two categories may belisted.10.5 Report the setup of the digital ac
40、quisition and evaluation: exposure time and threshold value.10.6 White AreaReport the ratio of area of the undispersed filler to the total area.FIG. 4 Example HistogramD7723 18410.7 Compound IdentificationWhen possible, list pertinent information regarding the following:10.7.1 Filler, type and loadi
41、ng,10.7.2 Other fillers, type and loading,10.7.3 Polymer type, and10.7.4 Extender oil, type and loading.11. Precision and Bias11.1 A precision and bias study for this test method is currently being planned.12. Keywords12.1 filler; incorporation; macro-dispersion; micro-roughness; reflected light mic
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