1、Designation: D 4895 04Standard Specification forPolytetrafluoroethylene (PTFE) Resin Produced FromDispersion1This standard is issued under the fixed designation D 4895; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of la
2、st revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the Department of Defense.1. Scope*1.1 This specification2covers dry-powder
3、resins of polytet-rafluoroethylene (PTFE) that have been prepared from disper-sions of PTFE by manufacturing techniques that involvecontrolled coagulation of the dispersion. These resins aregenerally known as “fine-powder” resins or “coagulated-dispersion powder” resins. The conversion of these resi
4、ns tofinished products normally involves a process called “pasteextrusion,” and sometimes involves formative processes suchas calendering. A volatile liquid is present as a processing aidduring these formative stages of conversion, and is subse-quently removed during the finishing stages of conversi
5、on.These PTFE resins are homopolymers of tetrafluoroethylene,or, in some cases, modified homopolymers containing not morethan 1 % by weight of other fluoromonomers. The usualmethods of processing thermoplastics generally are not appli-cable to these materials because of their viscoelastic properties
6、.The materials covered herein do not include mixtures of PTFEwith additives such as colors, fillers, or plasticizers; nor do theyinclude reprocessed or reground resin or any fabricated articlesbecause the properties of such materials have been irreversiblychanged when they were fibrillated or sinter
7、ed. The methodsand properties included are those required to identify thevarious resins. An additional procedure is provided in theappendix for further characterization of the resins.1.2 The values stated in SI units as detailed in IEEE/ASTMSI 10 are to be regarded as standard. The values given inbr
8、ackets are for information only.1.3 The following safety hazards caveat pertains only to theSpecimen Preparation Section, Section 9, and the Test MethodsSection, Section 10, of this specification: This standard doesnot purport to address all of the safety concerns, if any,associated with its use. It
9、 is the responsibility of the user of thisstandard to establish appropriate safety and health practicesand determine the applicability of regulatory limitations priorto use. See Warning note in 9.1.1 for a specific hazardsstatement.NOTE 1Information in this specification is technically equivalent to
10、related information in ISO 12086-1 and ISO 12086-2.2. Referenced Documents2.1 ASTM Standards:3D 618 Practice for Conditioning Plastics for TestingD 638 Test Method for Tensile Properties of PlasticsD 792 Test Methods for Specific Gravity (Relative Density)of Plastics by DisplacementD 883 Terminology
11、 Relating to PlasticsD 1895 Test Methods for Apparent Density, Bulk Factor,and Pourability of Plastic MaterialsD 3892 Practice for Packaging/Packing of PlasticsD 4052 Test Method for Density and Relative Density ofLiquids by Digital Density MeterD 4441 Specification for Aqueous Dispersions of Polyte
12、t-rafluoroethyleneD 4591 Test Method for Determining Temperatures andHeats of Transitions of Fluoropolymers by DifferentialScanning CalorimetryD 4894 Specification for Polytetrafluoroethylene (PTFE)Granular Molding and Ram Extrusion MaterialsE11 Specification for Wire-Cloth Sieves for Testing Pur-po
13、sesE29 Practice for Using Significant Digits in Test Data toDetermine Conformance with SpecificationsE 177 Practice for Use of the Terms Precision and Bias inASTM Test MethodsIEEE/ASTM SI 10 Use of the International System ofUnits (SI): The Modern Metric System2.2 ISO Standards:4ISO 12086-1 Plastics
14、 Fluoropolymer Dispersions and1This specification is under the jurisdiction of ASTM Committee D20 onPlastics and is the direct responsibility of Subcommittee D20.15 on ThermoplasticMaterials.Current edition approved Feb. 1, 2004. Published March 2004. Originallyapproved in 1989. Last previous editio
15、n approved in 1998 as D 4895 - 98.2Specifications for other forms of polytetrafluoroethylene are found in Specifi-cations D 4441 and D 4894.3For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volum
16、e information, refer to the standards Document Summary page onthe ASTM website.4Available from American National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036.1*A Summary of Changes section appears at the end of this standard.Copyright ASTM International, 100 Barr Harbor D
17、rive, PO Box C700, West Conshohocken, PA 19428-2959, United States.Molding and Extrusion MaterialsPart 1: Designationand SpecificationISO 12086-2 Plastics Fluoropolymer Dispersions andMolding and Extrusion MaterialsPart 2: Preparation ofTest Specimens and Determination of Properties3. Terminology3.1
18、 DefinitionsThe definitions given in TerminologyD 883 are applicable to this specification.3.2 Descriptions of Terms Specific to This Standard:3.2.1 bulk density, nthe mass in grams per litre of resinmeasured under the conditions of the test.3.2.2 extended specific gravity (ESG), nthe specific grav-
19、ity of a specimen of PTFE material molded as described in thisspecification and sintered (see 3.2.7) for an extended period oftime, compared to the sintering time for the measurement ofSSG (see 3.2.8), using the appropriate sintering schedule givenin this specification.3.2.3 lot, none production run
20、 or a uniform blend of twoor more production runs.3.2.4 preforming, vbcompacting powdered PTFE mate-rial under pressure in a mold to produce a solid object, calleda preform, that is capable of being handled. Molding andcompaction are terms used interchangeably with preformingfor PTFE.3.2.5 reground
21、resin, nresin produced by grinding PTFEmaterial that has been preformed but has never been sintered.3.2.6 reprocessed resin, nresin produced by grindingPTFE material that has been preformed and sintered.3.2.7 sintering, nas it applies to PTFE, a thermal treat-ment during which the PTFE is melted and
22、 recrystallized bycooling with coalescence occurring during the treatment.3.2.8 standard specific gravity (SSG), nthe specific grav-ity of a specimen of PTFE material molded as described in thisspecification and sintered using the appropriate sinteringschedule given in this specification.3.2.9 strai
23、ned specific gravity (strained SG), nthe specificgravity of a specimen of PTFE material molded, sintered, andstrained as described in this specification.3.2.10 stretching void index (SVI), na measure of thechange in specific gravity of PTFE material which has beensubjected to tensile strain as descr
24、ibed in this specification.3.2.11 thermal instability index (TII), na measure of thedecrease in molecular weight of PTFE material which has beenheated for a prolonged period of time.3.2.12 unstrained specific gravity (USG), nthe specificgravity, prior to straining, of a specimen of PTFE material use
25、din the Stretching Void Index Test (see 10.9) of this specifica-tion.4. Classification4.1 This specification covers the following types of PTFE:4.1.1 Type I and Type IIResin produced from dispersionand normally used with a volatile processing aid. These resinsall have the same requirements for bulk
26、density, particle size,water content, melting peak temperature, tensile, and elonga-tion. These resins are divided into four grades in accordancewith standard specific gravity (SSG), Thermal Stability Index(TII), and Stretching Void Index (SVI). Grades are divided intoclasses according to extrusion
27、pressure.NOTE 2See Tables 1 and 2 for details about grades and classes.4.2 A line callout system is used to specify materials in thisspecification. The system uses predefined cells to refer tospecific aspects of this specification, as illustrated as follows:SpecificationStandard NumberBlockType Grad
28、e Class Special Notes| | | | |Example: Specification I 2 CD 4895 - XXFor this example, the line callout would be Specification D4895 - XX, I2C, and would specify a coagulated dispersionform of polytetrafluoroethylene that has all of the propertieslisted for that type, grade, and class in the appropr
29、iate specifiedproperties or tables, or both, in the specification identified. Acomma is used as the separator between the standard numberand the type. Separators are not needed between the type,grade, and class.5Provision for Special Notes is included toallow other information to be provided when re
30、quired. Anexample would be in Specification D 3295 where dimensionsand tolerances are specified for each American Wire Gage(AWG) size within type and class. When special notes are used,they shall be preceded by a comma.5. Mechanical Properties5.1 The resins covered by this specification shall be ina
31、ccordance with the requirements prescribed in Tables 1 and 2,when tested by the procedures specified herein.6. Other Requirements6.1 The resin shall be uniform and shall contain no additivesor foreign material.5See the ASTM Form and Style Manual, available from ASTM Headquarters.TABLE 1 Detail Requi
32、rements for all Types,AGrades and ClassesTypeBulk Density,g/LParticle SizeAverageDiameter, mWater Content,max, %Melting PeakTemperature, CTensile Strength,min, MPaElongation at Break,min, %Initial SecondI 550 6 150 500 6 200 0.04B327 6 10 19 200II 550 6 150 1050 6 350 0.04B327 6 10 19 200AThe types,
33、 grades, and classes are not the same as those in previous editions of Specification D 4895.BGreater than 5.0C above the second melting peak temperature.D 4895 0426.2 The color of the material as shipped by the supplier shallbe natural white.6.3 For purposes of determining conformance, all specified
34、limits for this classification system are absolute limits, asdefined in Practice E29.6.3.1 With the absolute method, an observed value is notrounded, but is to be compared directly with the limiting value.Example: In Table 1 Type 4, Class B, under Specific Gravity,2.14 shall be considered as 2.14000
35、0 and 2.16 shall beconsidered 2.160000.7. Sampling7.1 Sampling shall be statistically adequate to satisfy therequirements in Section 11.8. Number of Tests8.1 Lot inspection shall include tests for bulk density,particle size, and extrusion pressure. Periodic tests shall consistof all the tests specif
36、ied in Tables 1 and 2 and shall be made atleast once per year.8.2 The tests listed in Tables 1 and 2, as they apply, aresufficient to establish conformity of a material to this specifi-cation. One set of test specimens as prescribed in Section 3shall be considered sufficient for testing each sample.
37、 Theaverage of the results for the specimens tested shall conform tothe requirements of this specification.9. Specimen Preparation9.1 Test Disks for Tensile Properties:9.1.1 Use the die shown in Fig. 1 for the molding of testdisks (see Note 2). Place flat aluminum disks, 0.1 to 0.4 mm0.004 in. to 0.
38、016 in. thick and 76 mm 3 in. in diameter, onboth sides of the resin. The test resin shall be near ambienttemperature prior to molding (see Note 3). WarningPTFEresins can evolve small quantities of gaseous products whenheated above 204C 400F. Some of these gases are harmful.Consequently, exhaust ven
39、tilation must be used wheneverthese resins are heated above this temperature, as they areduring the sintering operations that are a part of this specifi-cation. Since the temperature of burning tobacco exceeds204C 400F, those working with PTFE resins shall ensurethat tobacco is not contaminated.NOTE
40、 3For maximum precision, these weighing and preformingoperations shall be carried out at 23 6 2C 73.4 6 3.6F (the “nearambient” temperature referred to herein). These operations shall not beperformed at temperatures below 21C 70F due to the crystallinetransition that occurs in PTFE in this temperatu
41、re region which leads topossible cracks in sintered specimens and differences in specimen density(as well as changes in other physical properties). Problems caused by theeffect of temperature on the specific gravity or density of PTFE shall beminimized when the measurement is made using immersion pr
42、ocedures ifa sensitive thermometer (for example, one reading 6 0.1C) is used in theliquid and the temperature is adjusted to be at least 22C.9.1.2 Screen 14.5 g of PTFE resin through a No. 10 sieveinto the die. Adjust the lower plug height to allow the resin inthe die can be leveled by drawing a str
43、aightedge in contact withthe top of the die across the top of the die cavity. Insert the diein a suitable hydraulic press and apply pressure gradually (seeNote 4) until a pressure of 14 MPa 2030 psi is attained. Holdthis pressure for 3 min. Remove the disk from the die. Write thesample identificatio
44、n number on the preform using an appro-priate marker that will not effect the PTFE during sintering.NOTE 4As a guide, increasing the pressure at a rate of 3.5 MPa 500psi/min is suggested until the desired maximum pressure is attained.9.1.3 Place the sintering oven in a laboratory hood (or equipit wi
45、th an adequate exhaust system) and sinter the preforms inaccordance with Table 3, Procedure A (see Note 5).NOTE 5Although the rate of heat application is not critical, thecooling cycle is most important and the conditions cited in this proceduremust be followed very closely. If they are not followed
46、, the crystallinity ofthe disks and the resulting physical properties will be markedly changed.Therefore, the use of a programmed oven is recommended for the mostprecise sintering cycle control and the hood window shall be left downduring the entire sintering procedure, the latter being an important
47、 safetyconsideration.9.2 Test Specimens for Standard Specific Gravity and Ther-mal Instability Index:9.2.1 A cylindrical preforming mold, 29-mm 1.14-in. in-ternal diameter by at least 76 mm 3 in. deep, is used toprepare the preforms. Clearance shall be sufficient to ensureescape of air during pressi
48、ng. Place flat aluminum foil disks,normally 0.13 mm 0.005 in. thick and 29 mm 1.14 in. indiameter on both sides of the resin. The test resin shall be nearambient temperature prior to molding (see Note 3).TABLE 2 Detail Requirements for All Types,AGrades and ClassesType Grade ClassStandard Specific G
49、ravityExtrusion Pressure, MPaThermal Instability Index,maxStretching Void Index,maxmin maxI 1 A 2.14 2.18 5 to 15B50 NACB 2.14 2.18 15 to 55D50 NACC 2.14 2.18 15 to 75E50 NAC2 A 2.17 2.25 5 to 15B50 NACB 2.17 2.25 15 to 55D50 NACC 2.17 2.25 15 to 75E50 NAC3 C 2.15 2.19 15 to 75E15 200D 2.15 2.19 15 to 65E15 100E 2.15 2.19 15 to 65E50 2004 B 2.14 2.16 15 to 55D15 50II 1 A 2.14 2.25 5 to 15B50 NACAThe types, grades, and classes are not the same as those in previous editions of Specification D 4895.BTested at a reduction ratio of
