1、Designation: D351 14Standard Classification forNatural Muscovite Block Mica and Thins Based on VisualQuality1This standard is issued under the fixed designation D351; 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.This standard has been approved for use by agencies of the U.S. Department of Defense.1. Scope1.1 This classification covers the deter
3、mination of commer-cially available natural muscovite block mica and is intended tobe independent of the basic color of the mica or its source.1.2 Muscovite mica is characterized by having an opticalaxial angle between 50 and 75 (see Appendix X1); and has aweight loss when heated for 5 min at 600C n
4、ot exceeding0.2 % (based on the weight after drying at 120C).1.3 The visual system of classifying the quality of naturalmuscovite mica covered by this specification is based uponrelative amounts of visible foreign inclusions such as airbubbles, stains, and spots in combination with relative amountsa
5、nd types of waviness, as well as other physical properties. Inthis system, a perfectly clear, transparent, flat specimen of micais the visual standard of perfection. Increasing amounts ofvisual defects lower the visual quality, and a total of 13 levelsof visual quality are covered by this standard.
6、This method ofclassification, generally known as the Bengal India System, ispurely qualitative and is entirely dependent on personal opin-ion and judgment.1.4 The standards for visual quality classification that arecovered in this classification are the best commercially avail-able concept of the va
7、rious qualities and their relative posi-tions. Variations in the methods of using and applying thesestandards from those herein defined may be specified by thepurchaser, or defined by agreement between the supplier andthe purchaser.1.5 Standard size classifications are defined, based uponavailable u
8、sable rectangular areas and the minimum dimen-sions of the rectangles that the pieces will yield. Precautions tobe taken in making thickness measurements are also described.1.6 This standard covers the following two definite forms ofcommercial preparation:1.6.1 Form 1Full-trimmed natural block mica,
9、 0.007 in.(0.178 mm) minimum thickness.1.6.2 Form 2Partially-trimmed natural block mica, 0.007in. minimum thickness.1.7 The basic color of mica, such as white, ruby, light green,dark green, brownish green, and rum, as well as other colors,and the method of controlling the color and other problemsass
10、ociated with the basic color, are not a part of this classifi-cation.1.8 The values stated in inch-pound units are to be regardedas standard. The values given in parentheses are mathematicalconversions to SI units that are provided for information onlyand are not considered standard.1.9 Section 5 is
11、 technically identical to procedures specifiedin ISO 67-1981.1.10 Section 6 differs somewhat in procedure from ISO5972-1978, but data obtained by either should be identical.1.11 Section 7 is technically identical to procedures speci-fied in ISO 2185-1972.2. Referenced Documents2.1 ASTM Standards:2D3
12、74 Test Methods for Thickness of Solid Electrical Insu-lation (Metric) D0374_D0374MD1711 Terminology Relating to Electrical Insulation2.2 ISO Publications:ISO 67-1981 Muscovite Mica Blocks, Thins, and FilmsGrading by Size3ISO 2185-1972 Muscovite Mica Blocks, Thins, and FilmsVisual Classification3ISO
13、 5972-1978 Mica Blocks, Thins, Films, and SplittingsMeasurement of Thickness31This classification is under the jurisdiction of ASTM Committee D09 onElectrical and Electronic Insulating Materials and is the direct responsibility ofSubcommittee D09.01 on Electrical Insulating Products.Current edition
14、approved Jan. 15, 2014. Published March 2014. Originallyapproved in 1932. Last previous edition approved in 2008 as D351 97 (2008)1.DOI: 10.1520/D0351-14.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMS
15、tandards volume information, refer to the standards Document Summary page onthe ASTM website.3Available from American National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036, http:/www.ansi.org.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohoc
16、ken, PA 19428-2959. United StatesThis international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organiz
17、ation Technical Barriers to Trade (TBT) Committee.13. Terminology3.1 For definitions of terms relating to mica refer to Termi-nology D1711, Part III.3.2 Definitions of Terms Specific to This Standard:3.2.1 “A”a series of rulings or striations intersecting at anangle of about 60.3.2.2 blocksmica thic
18、kness of 0.007 in. (0.178 mm) mini-mum thickness, full-trimmed, unless otherwise designated.3.2.3 buckleone or more large depression(s) and eleva-tion(s).3.2.4 cracksirregular fractures within the crystal that maybe natural or may arise from blasting, rough handling, etc.3.2.5 full-trimmed micamica
19、trimmed on all sides with allcracks, reeves, and cross-grains removed.3.2.6 haircracks or hairline cracksminute, irregularcracks that are barely noticeable until mica is split into films,resulting in production of torn films.3.2.7 reeves or cross grainstangled laminations givingimperfect cleavage, t
20、hat results in tears or breaks duringsplitting.3.2.8 ribboned or rules micamica that breaks into narrowstrips because of parallel fractures.3.2.9 ribs or ridgescrenulations in the form of steps.3.2.10 ripplemultiple short waves.3.2.11 stainsstains arise from foreign materials, resultingin a partial
21、or total loss of transparency. They may be in theform of specks or patches of appreciable area for example,slight stain, “vegetable” stain, clay stain, black stain, red stain,black speckled, light dot or spot, black, red or green dot or spot,etc. (see “inclusions” in Terminology D1711).3.2.12 stones
22、 and stone holessmall embedded crystals orholes resulting from them.3.2.13 thinsknife-dressed mica, 0.002 in. (0.05 mm) toless than 0.007 in. (0.18 mm) in thickness. They may beclassified as follows:3.2.13.1 Thins, 0.002 to 0.004 in. (0.05 to 0.10 mm), and3.2.13.2 Thick-thins, 0.004 to 0.007 in. (0.
23、10 to 0.18 mm).3.2.14 unmanufactured micacommercial form of micaknown as blocks, thins, films, and splittings, as described.3.2.15 wavesalternate elevations and depressions thatmay be classified as slight, medium, or heavy.4. Significance and Use4.1 The properties included in this standard are those
24、required to control the visual quality, usable area, thickness,hardness, and stiffness.5. Grading for Size5.1 Full-TrimmedAll full-trimmed mica blocks and thinsshall be fully trimmed to remove all cracks, holes, reeves, andcross-grains according to the quality desired.As far as possible,all marginal
25、 cracks should be removed by recutting. Theaverage area of the pieces for Grade 4 and larger shall be notmore than 1.54 times the average area of the largest usablerectangles. This would constitute a minimum yield of 65 %.For Grades 5 and smaller, the average area of the pieces shallbe not more than
26、 two times the average area of the largestusable rectangles. This would constitute a yield of 50 %.5.2 Half-TrimmedFor half-trimmed mica, follow the grad-ing described in 5.1 for trimmed sides with no cracks extendingfrom the trimmed sides, except for sizes 6 and 512 on whichonly side must be trimme
27、d free of cracks. On the untrimmedsides, no defects of the designated quality are acceptable withinthe minimum rectangle of the designated grade.5.3 Natural Block and ThinsNatural block and thins,muscovite mica shall be graded for size according to the areaof the rectangle (maximum rectangle for ful
28、l-trimmed, maxi-mum rectangle of designated quality for half-trimmed) havingat least the minimum dimension of one side for the specifiedgrade. The area within such a rectangle shall meet therequirements of the quality specified by the purchaser as listedin Table 1.5.4 Method of Grading for SizeThe S
29、tandardASTM Chartshown in Fig. 1 shall be used for grading natural block andthins, muscovite mica according to size. In grading naturalblock mica and thins for size, all dimensions apply to thesmaller surface measured from the foot of the bevel-trimmededge. The specimen to be graded shall be laid up
30、on the chart sothat it covers point O and has its maximum and minimumdimensions extending along and covering lines OA and OB,respectively. The specimen shall be shifted until the usable areacompletely covers the largest rectangle, determined by adiagonal extending from point O to or beyond a point o
31、n anyof the curves. The number of the curve at the greatest distancefrom O cut by the diagonal of the rectangle designates thegrade of the specimen.6. Thickness of Block Mica6.1 Measure the thickness with a micrometer as specified inTest Methods D374. In determining thickness of mica thatmust be kep
32、t within small permissible variations, or where twoor more specimens are to be measured at once, use Method ATABLE 1 ASTM Grade Sizes of Muscovite Uncut Mica Block andThinsASTMGradeSizesArea ofMinimumRectangleMinimumDimen-sion ofOne Sidein.2Equiva-lent, cm2in.Equiva-lent, mmOOEE Special 100 650 4 10
33、0OEE Special 80 520 4 100EE Special 60 390 4 100E Special 48 310 4 100A-1 (Special) 36 235 312 89No. 1 24 155 3 76No. 2 15 97 2 51No. 3 10 65 2 51No. 4 6 40 112 38No. 5 3 20 1 25No. 512 214 1578 22No. 6 1 6.534 19D351 142of Test Methods D374. Where the maximum accuracy is notrequired, Method B may b
34、e used.6.2 Because of the abrasive nature of mica, test the microm-eter frequently for conformity to the requirements specified inTest Methods D374. Clean the anvil and spindle as frequentlyas necessary to prevent the accumulation of mica dust on thesurfaces and to preserve the accuracy of the measu
35、rements. Toclean, close the micrometer lightly on a clean sheet of bondpaper and move the paper between the surfaces.6.3 Be careful, when moving from one measurement loca-tion to another, to maintain the surfaces of the anvil and spindleparallel to the surfaces of the specimen at all times, so as to
36、avoid scratching the mica and accumulating mica dust underthe micrometer surfaces, thereby causing false readings.7. Classification of Visual Quality of Block Mica7.1 The classification of the visual quality of muscoviteblocks and thins shall fall into the following thirteen catego-ries:7.1.1 V-1 Cl
37、ear7.1.2 V-2 Clear and Slightly Stained7.1.3 V-3 Fair Stained7.1.4 V-4 Good Stained7.1.5 V-5 Stained A Quality7.1.6 V-5.1 Stained A1 Quality7.1.7 V-6 Stained B Quality7.1.8 V-7 Heavy Stained7.1.9 V-8 Densely Stained7.1.10 V-9 Black Dotted7.1.11 V-10 Black Spotted7.1.12 V-11 Black Stained7.1.13 V-12
38、Black/Red Stained7.2 The classification of the visual quality of block micashall be judged in accordance with the requirements specifiedin Table 2 using the visual descriptions given.8. Keywords8.1 Bengal India System; block; classification; foreign in-clusions; form; grading; muscovite mica; size;
39、thins; visualqualityNOTE 1This chart may be readily extended for Grades OOEE Special, OEE Special, EE Special, and E Special, using the information given in Table1 of ASTM Specification D351.FIG. 1 ASTM Chart for Grading Natural Muscovite Block and Film MicaD351 143TABLE2QualityClassificationofMusco
40、viteBlockandThinsBasedonVisualPropertiesA,B,C,D,E,F,G,H,I,JASymbols:=PermissibleNotpermissibleSPermissibleonlyifspecifiedFewandtinyinone-fourthofusablearea.BInone-halfusableareaCSlightDIntwo-thirdsusableareaEUniformlydistributedD351 144FNotheavilyconcentratedovermorethananareaequivalentto14in.square
41、(6.4mmsquare)forgrade5andupandovermorethananareaequivalentto18in.2(3.2mm2)forGrade512andlowerGNotexceedingtwospeckswithintheusableareaHMediumIHeavyJDispersedblackdotsNote1Thevisualpropertiesofblockmicausuallyarejudgedunderthefollowinglightconditions:ForstainsandinclusionsTransmitteddaylightoritsequi
42、valent.ForairinclusionsReflecteddaylightoritsequivalent.Forwaves,buckles,ridges,etc.Reflecteddaylightoritsequivalentwheredistortionofparallelandverticallinesofreflectedimage,suchasawindowframe,canbejudged.Note2Thehardnessormechanicalpropertiesofmuscovitemicaareusuallyjudgedbyasharp,clearringwhenmica
43、isdroppedonahardsurface.Note3Muscovitemicaoccursinvariouscolorswhicharemorepronouncedthethickertheblock.Sometypicalcolorsareruby,white,lightgreen,rum,etc.Note4Cracks,tears,stones,orpinholesarejudgedbytransmitteddaylightorequivalent.Note5Rigidityisjudgedbytherelativestiffnesswhenflexingwiththefingers
44、.Note6SeeSection3fordefinitionoftermsusedinTable2.Note7Thefollowingareverbaldescriptionsoftheclassificationofmuscoviteblocksandthins,judgedintermsofrequirementsofTable2:V-1ClearHard,ofuniformcolor,flat,freefromallstainsandforeigninclusions,waves,cracks,buckles,andothersimilardefects.V-2ClearandSligh
45、tlyStainedHard,ofuniformcolor,nearlyflat,freefromallvegetableandmineralstains,cracks,bucklesandothersimilardefects,andforeigninclusionsexceptforafewtinyairinclusionsinnotmorethanone-fourthoftheusablearea.Slightcrystallographicdiscolorationispermittedtoalimitedextent.V-3FairStainedHard,ofuniformcolor
46、,freeofallvegetableandmineralstains,cracks,bucklesandothersimilardefects,andforeigninclusions,exceptmaybeslightlywavy,andmaycontainslightairinclusionsinnotmorethanone-halfoftheusablearea,theseinclusionsshouldnotbeconcentrated.Slightcrystallographicdiscolorationispermittedtoalimitedextent.V-4GoodStai
47、nedHard,freeofvegetableormineralstains,cracks,bucklesandothersimilardefects,andforeigninclusions,exceptmaybemediumwavybutnotrippledandmaycontainmediumairinclusionsinnotmorethantwo-thirdsoftheusablearea,butmaynothaveheavilyconcentratedairinclusionsinanyoftheusablearea.Slightcrystallographicdiscolorat
48、ionispermittedtoalimitedextent.V-5StainedAQualityHard,freeofcracksandothersimilardefectsandforeigninclusions,exceptmaybemediumwavyandmaycontainslightvegetablestainsandtheentireareamayhaveairinclusionsifnotheavilyconcentrated.Crystallographicdiscolorationispermitted.V-5.1StainedA1QualityHard,freeofcr
49、acksandothersimilardefectsandforeigninclusionsexceptmaybewavyandmaycontainslightvegetablestains,slightmineralstainsnotexceedingtwospeckswithintheusableareaandtheentireareamayhaveairinclusionsifnotheavilyconcentratedovermorethanareaequivalentto14in.square(6.4mmsquare)forgrade5andupandovermorethananareaequivalentto18in.2(3.2mm2)forgrade512andbelow.Crystallographicdiscolorationispermitted.V-6StainedBQualityHard,freeofcracks,andothersimilardefectsandforeigninclusions,exceptmaybewavyandslightlybuckledandmaycontainheavya
