1、Designation: D3849 14D3849 14aStandard Test Method forCarbon BlackMorphological Characterization of CarbonBlack Using Electron Microscopy1This standard is issued under the fixed designation D3849; the number immediately following the designation indicates the year oforiginal adoption or, in the case
2、 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 (1) the morphological (for example, size and shape) characterization
3、 of carbon black fromtransmission electron microscope images which are used to derive the mean particle and aggregate size of carbon black in the dry(as manufactured) state, from CAB chip dispersion or removed from a rubber compound and (2) the certification of mean particlesize using a correlation
4、based on statistical thickness surface area measurements.1.2 The values stated in SI units are to be regarded as the standard. The values in parentheses are for information only.1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the respo
5、nsibilityof the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatorylimitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D3349 Test Method for Absorption Coefficient of Ethylene Polymer Material Pigmented with Carbon
6、BlackD6556 Test Method for Carbon BlackTotal and External Surface Area by Nitrogen Adsorption3. Terminology3.1 Definitions:3.1.1 General:3.1.1.1 carbon black particlea small spheroidally shaped, paracrystalline, non-discrete component of an aggregate; it can onlybe separated from the aggregate by fr
7、acturing; carbon black particle size is a distributional property; therefore, the term particlesize implies the mean value from multiple measurements.3.1.1.2 carbon black aggregatea discrete, rigid colloidal entity that is the smallest dispersible unit; it is composed ofextensively coalesced particl
8、es; carbon black aggregate size is a distributional property; therefore, the term aggregate size impliesthe mean value from multiple measurements.3.1.1.3 statistical thickness surface area (STSA)the external specific surface area of carbon black that is calculated fromnitrogen adsorption data using
9、the de Boer theory and a carbon black-specific model.3.1.1.4 glow dischargea plasma of ionized gas that is formed in a high-voltage field at pressures of about 3 to 20 Pa (25 to150 10-3 torr); an alternating current (a-c) glow discharge using air is effective in cleaning and oxidizing the surface of
10、 carbonsubstrates to improve the wetting characteristics of polar vehicles containing pigment dispersions.3.1.1.5 substratea thin film that is used to support electron microscope specimens; evaporated carbon films are commonlyused because of relatively good mechanical strength, stability, and conduc
11、tivity.3.1.2 Aggregate Dimensional Properties from Image Analysis:3.1.2.1 area (A)the two-dimensional projected area of the carbon black aggregate image.3.1.2.2 perimeter (P)the total boundary length of an aggregate.1 This test method is under the jurisdiction of ASTM Committee D24 on Carbon Black a
12、nd is the direct responsibility of Subcommittee D24.81 on Carbon BlackMicroscopy and Morphology.Current edition approved Jan. 1, 2014Nov. 1, 2014. Published January 2014November 2014. Originally approved in 1980. Last previous edition approved in 20132014as D3849 13.D3849 14. DOI: 10.1520/D3849-14.1
13、0.1520/D3849-14A.2 For referencedASTM standards, visit theASTM website, 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
14、 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, ASTM recommends that users consult prior editions as appropriate. In all cases only the
15、current versionof the standard as published by ASTM is to be considered the official document.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States13.1.2.3 volume (V)an estimate of the volume of the carbon black aggregate using stereologica
16、l principles.3.1.3 Image Analysis:3.1.3.1 dilationthe converse of erosion; this process is accomplished by changing any OFF pixel to ON if it has greater thana preset minimum of ON neighbors, causing image features to grow in size, which fills in small breaks in features, internal voids,or small ind
17、entations along the feature surface.3.1.3.2 erosionthe process by which image features are reduced in size by selectively removing pixels from their periphery;it consists of examining each binary pixel and changing it from ON to OFF if it has greater than a preset minimum of neighborsthat are OFF; i
18、t serves a number of useful functions, such as smoothing feature outlines and separating features touching each other.3.1.3.3 featureareas within a single continuous boundary that have gray-level ranges that allow them to be distinguished fromthe background area outside the feature via thresholding.
19、3.1.3.4 thresholdingselecting a range of brightness such that discrimination is possible between the feature and thebackground; the gray levels within carbon black images become lower with decreasing particle size.4. Significance and Use4.1 Carbon black morphology significantly affects the transient
20、 and end-use properties of carbon black loaded polymer systems.Acarbon blacksblacks particle size distribution is its single most important property, and it relates to degree of blackness, rubberreinforcement, and ability to impart UV protection. For a given loading of carbon black, blackness, reinf
21、orcement, and UVprotection increase with smaller particle size. Aggregate size and shape (structure) also affect a carbon blacks end-useperformance, as higher carbon black structure increases viscosity and improves dispersion. The stiffness (modulus) of elastomersystems becomes significantly higher
22、with increasing structure. The preferred method for measuring carbon black morphology (forexample, size and shape) is transmission electron microscopy (TEM), but due to the semi-quantitative nature of TEM, it is notsuited for mean particle size (MPS) certification. While useful morphological informa
23、tion can be obtained from TEMmeasurements within a laboratory, due to their inherent between-laboratory variability, TEM generated values should not be usedfor specification purposes.4.2 Certification of carbon blacks for UV protection (weatherability) in certain plastics applications has historical
24、ly beenperformed using TEM generated mean particle size values. ASTM Committee D24 has demonstrated that due to challenges withobtaining quantitative primary particle size data, particularly between laboratories, a qualification test based on surface area hasbeen implemented, as detailed in Test Met
25、hod B.4.3 Carbon black aggregate dimensional and shape properties are dependent upon the nature of the system in which the sampleis dispersed, as well as the mixing procedure.Test Method A Morphological Evaluation (Semi-Quantitative) Via Transmission Electron Microscopy5. Summary of Test Method5.1 T
26、ransmission electron microscopy (TEM) is utilized to measure the morphological properties of carbon black. A variety ofdispersion methods are offered depending upon the sample type. Both dry black and CAB chip dispersions are used for measuringthe morphology of bulk carbon black.Apyrolysis technique
27、 is included that facilitates the removal of carbon black from vulcanizedrubber. This aforementioned technique can be employed to identify the carbon black type from an end use product. It should benoted that the accuracy and precision of Method A is insufficient for generating quantitative data as
28、required in the case of MPScertification. Please refer to Method B for MPS certification.6. Apparatus6.1 Electron Microscope, transmission-type, with a point-to-point resolution of 1.0 nm or better. Operating voltages should behigh enough to provide the desired resolution and low enough to produce i
29、mages of sufficient contrast. Recommended voltagescan be in the 60 to 120 kV range. The microscope column should contain a liquid nitrogen-cooled anti-contamination device ora “cold finger” to reduce sample contamination and to maintain column cleanliness. For image acquisition, the microscope shoul
30、dinclude a charge-coupled device (CCD) camera mounted either above or below the instruments viewing chamber.6.2 Image Analysis System, consisting at minimum of a TEM-interfaced camera capable of 640 480 pixel or better resolution,a computer equipped with frame grabbing hardware to capture TEM images
31、 digitally, and software to perform morphologicaloperations and measurements on image features and store resulting data. Operations must include background/noise elimination,thresholding, and edge smoothing. Area and perimeter are then measured on features in the processed images.6.3 Two-Roll Mill.6
32、.4 Vacuum Evaporator, standard-type, for preparing carbon films to be used as substrates for electron microscopy. Theevaporator should be capable of reducing the absolute pressure to 1.3 mPa (1 10-5 torr) and should also contain the necessaryapparatus for a-c glow discharge.6.5 Ultrasonic Generator,
33、 variable power tank-type or probe that provides sufficient energy to give acceptable dispersion.D3849 14a26.6 Dry Box, capable of maintaining a relative humidity level of no greater than 30 %.6.7 Analytical Balance, with an accuracy of about 0.5 mg.6.8 Electrically Heated Tube Furnace, capable of b
34、eing heated to 800 to 900C under an inert environment, with the ability tointroduce and remove the sample boat to the heated zone without allowing oxygen intrusion.6.9 Pyroprobe, capable of being heated from 150 to 1000C in an inert environment.6.10 Carbon Rods, approximately 3.1 mm in diameter.6.11
35、 Carbon Rod Sharpener.6.12 Glass Microscope Slides, 25 by 75-mm.6.13 Test Tubes, 75 by 10-mm, 4-cm3 capacity, 0.5-mm wall thickness, with corks.6.14 Transfer Pipets, disposable Pasteur-type, 225 mm long, 1-mm inside diameter at tip.6.15 Rubber Bulbs, for pipets.6.16 Glass Vials, 40-cm3 capacity, wit
36、h solvent-resistant tops.6.17 Bchner Funnel, No. 3, 111-mm inside diameter.6.18 Filter Paper, general purpose.6.19 Carbon Coated Electron Microscope Specimen Grids, 3-mm diameter, 200 to 300 mesh. Commercially available or canbe prepared as described in Annex A1.6.20 Wire Screening, with openings ap
37、proximately 1 mm2.6.21 Tweezers, fine-tipped.6.22 Spatulas, micro-type with V-shaped spoon that is approximately 2 mm wide at top and 12.5 mm long.6.23 Fluorocarbon Duster.6.24 Lens Tissue, lint-free.6.25 Porcelain Boats, for pyrolysis, 98 mm long, 15 mm wide at top.6.26 Centrifuge, high speed (15 0
38、00 to 20 000 r/min) with head for 75 by 10 mm test tubes.6.27 Beakers, 2000-cm3 capacity.7. Reagents and Materials7.1 Chloroform, reagent grade.7.2 Tetrahydrofuran (THF), reagent grade.7.3 1,2-Dichloroethane, reagent grade.7.4 Ethyl Acetate, reagent grade.7.5 Poly (Vinyl Formal) Resin, Grade 15/95.7
39、.6 Cellulose Acetate Butyrate Resin (CAB).7.7 Phthalate-Type Plasticizer (such as santicizer).8. Sample PreparationDispersion Procedures8.1 Dry Carbon Black (Sonic Bath):8.1.1 Weigh 8 to 10 mg of carbon black into a test tube containing 1 cm3 of solvent (typically chloroform or THF).NOTE 1With exper
40、ience, it may not be necessary to weigh each carbon black sample, as an estimated amount from the microspatula may be sufficient.There is considerable latitude in the amount of carbon black used. The finer N100 and N200 blacks may require somewhat less carbon black than thecoarser semi-reinforcing t
41、ypes.8.1.2 Adjust the power of the ultrasonic bath for maximum agitation; this may require that the water level be adjusted. As theultrasonic energy heats the water in the bath, ice should be added to control the temperature in order to maintain maximumdispersive capability.8.1.3 Place the stoppered
42、 test tube containing the carbon black and solvent mixture into the most intense part of the ultrasonicfield and allow the mixture to agitate for 3 to 5 min. The test tube should be held with tongs or mounted in a simple wire holder.8.1.4 Transfer a small portion of the concentrated carbon black-sol
43、vent mixture into another test tube containing 1 cm3 of freshsolvent. The amount of concentrate required increases with particle size. Blend the mixture by repeatedly transferring the samplebetween the transfer pipet and the test tube, then cork the test tube and repeat the ultrasonic dispersion pro
44、cedure.D3849 14a38.1.5 Check the concentration of the diluted dispersion by extracting a small amount into the tip of the pipet and viewing againsta white background. For tread grade carbon blacks, the dispersions should be relatively transparent, becoming somewhat darkerwith increasing particle siz
45、e. The diluted dispersions for very coarse carbon blacks such as N700 to N900 series will be on thethreshold of complete opacity. If necessary, adjust the concentration by adding more concentrate or solvent as required, then repeatthe ultrasonic agitation. The volume of the carbon black-solvent mixt
46、ure should be maintained at approximately 1 cm3. Ifconsiderable dilution is required, the excess volume above 1 cm3 should be discarded.NOTE 2Areasonable degree of latitude exists for achieving the proper concentration levels in the final dispersions for different grades of carbon black.Concentratio
47、n and overall dispersion quality are best determined by screening the actual specimens in the electron microscope and then making thenecessary adjustments.8.1.6 Place a specimen grid with carbon substrate (film side up) on a piece of filter paper. Remove a small amount of the finaldiluted dispersion
48、 using a fresh pipet and place one drop on the grid as close to the center as possible, from a height of about 12mm.Allow the specimen to dry for about 1 min on a piece of filter paper.This specimen preparation procedure should be performedin a dry box if the relative humidity in the room exceeds 30
49、 %.8.1.7 ForTEM grids that contain formvar or residual CAB (CAB chip dispersions), place theTEM grid in an appropriate sampleholder, place in the pyrolysis chamber and allow adequate time for the chamber to be purged by an inert gas to prevent oxidationof the sample. Pyrolize the specimen grid at a sufficient temperature (typically greater than 550C) to remove the poly (vinylformal) film or CAB, or both.8.1.8 Acceptable dispersions of a carbon black in the dry state and removed from a rubber compound (SBR) are illustrated forN-220 and N-774 car
