1、Designation: D4895 16D4895 18Standard Specification forPolytetrafluoroethylene (PTFE) Resin Produced FromDispersion1This standard is issued under the fixed designation D4895; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year
2、 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.This standard has been approved for use by agencies of the U.S. Department of Defense.1. Scope*1.1 This specification2 covers
3、polytetrafluoroethylene (PTFE) prepared by coagulation of a dispersion. These PTFE resins arehomopolymers of tetrafluoroethylene or modified homopolymers containing not more than 1 % by weight of other fluoromono-mers. The materials covered herein do not include mixtures of PTFE with additives such
4、as colors, fillers, or plasticizers; nor dothey include reprocessed or reground resin or any fabricated articles because the properties of such materials have been irreversiblychanged when they were fibrillated or sintered.1.2 The values stated in SI units as detailed in IEEE/ASTM SI-10 are to be re
5、garded as standard. The values given inparentheses are for information only.1.3 The following safety hazards caveat pertains only to the Specimen Preparation Section, Section 9, and the Test MethodsSection, Section 10, of this specification: This standard does not purport to address all of the safet
6、y concerns, if any, associatedwith its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determinethe applicability of regulatory limitations prior to use. See Warning note in 9.1.1 for a specific hazards statement.NOTE 1Information i
7、n this specification is technically equivalent to related information in ISO 12086-1ISO 20568-1 and ISO 12086-2.ISO 20568-2.1.4 This international standard was developed in accordance with internationally recognized principles on standardizationestablished in the Decision on Principles for the Devel
8、opment of International Standards, Guides and Recommendations issuedby the World Trade Organization Technical Barriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:3D618 Practice for Conditioning Plastics for TestingD638 Test Method for Tensile Properties of PlasticsD792 Test M
9、ethods for Density and Specific Gravity (Relative Density) of Plastics by DisplacementD883 Terminology Relating to PlasticsD1708 Test Method for Tensile Properties of Plastics by Use of Microtensile SpecimensD1895 Test Methods for Apparent Density, Bulk Factor, and Pourability of Plastic MaterialsD3
10、892 Practice for Packaging/Packing of PlasticsD4052 Test Method for Density, Relative Density, and API Gravity of Liquids by Digital Density MeterD4441 Specification for Aqueous Dispersions of PolytetrafluoroethyleneD4591 Test Method for Determining Temperatures and Heats of Transitions of Fluoropol
11、ymers by Differential ScanningCalorimetryD4894 Specification for Polytetrafluoroethylene (PTFE) Granular Molding and Ram Extrusion MaterialsE11 Specification for Woven Wire Test Sieve Cloth and Test SievesE29 Practice for Using Significant Digits in Test Data to Determine Conformance with Specificat
12、ionsE177 Practice for Use of the Terms Precision and Bias in ASTM Test Methods1 This specification is under the jurisdiction of ASTM Committee D20 on Plastics and is the direct responsibility of Subcommittee D20.15 on Thermoplastic Materials.Current edition approved May 1, 2016Nov. 1, 2018. Publishe
13、d May 2016November 2018. Originally approved in 1989. Last previous edition approved in 20152016 asD4895 - 15.D4895 16. DOI: 10.1520/D4895-16.10.1520/D4895-18.2 Specifications for other forms of polytetrafluoroethylene are found in Specifications D4441 and D4894.3 For referencedASTM standards, visit
14、 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 intended only to provide the user of an ASTM standard
15、 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 current versionof the standard as published by ASTM is
16、 to be considered the official document.*A Summary of Changes section appears at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1IEEE/ASTM SI-10 Use of the International System of Units (SI): The Modern Metric
17、System2.2 ISO Standards:4ISO 12086-1ISO 20568-1 Plastics Fluoropolymer Dispersions and Molding and Extrusion MaterialsPart 1: Designation andSpecificationISO 12086-2ISO 20568-2 Plastics Fluoropolymer Dispersions and Molding and Extrusion MaterialsPart 2: Preparation ofTest Specimens and Determinatio
18、n of PropertiesISO 13322-2 Particle size analysisImage analysis methodsPart 2: Dynamic image analysis methods3. Terminology3.1 DefinitionsThe definitions given in Terminology D883 are applicable to this specification.3.2 Definitions of Terms Specific to This Standard:3.2.1 bulk density, nthe mass in
19、 grams per litre of resin measured under the conditions of the test.3.2.2 extended specific gravity (ESG), nthe specific gravity of a specimen of PTFE material molded as described in thisspecification and sintered (see 3.2.7) for an extended period of time, compared to the sintering time for the mea
20、surement of SSG(see 3.2.8), using the appropriate sintering schedule given in this specification.3.2.3 lot, none production run or a uniform blend of two or more production runs.3.2.4 preforming, vbcompacting powdered PTFE material under pressure in a mold to produce a solid object, called apreform,
21、 that is capable of being handled. Molding and compaction are terms used interchangeably with preforming for PTFE.3.2.5 reground resin, nresin produced by grinding PTFE material that has been preformed but has never been sintered.3.2.6 reprocessed resin, nresin produced by grinding PTFE material tha
22、t has been preformed and sintered.3.2.7 sintering, nas it applies to PTFE, a thermal treatment during which the PTFE is melted and recrystallized by coolingwith coalescence occurring during the treatment.3.2.8 standard specific gravity (SSG), nthe specific gravity of a specimen of PTFE material mold
23、ed as described in thisspecification and sintered using the appropriate sintering schedule given in this specification.3.2.9 strained specific gravity (strained SG), nthe specific gravity of a specimen of PTFE material molded, sintered, andstrained as described in this specification.3.2.10 stretchin
24、g void index (SVI), na measure of the change in specific gravity of PTFE material which has been subjectedto tensile strain as described in this specification.3.2.11 thermal instability index (TII), na measure of the decrease in molecular weight of PTFE material which has been heatedfor a prolonged
25、period of time.3.2.12 unstrained specific gravity (USG), nthe specific gravity, prior to straining, of a specimen of PTFE material used in theStretching Void Index Test (see 10.9) of this specification.4. Classification4.1 This specification covers the following types of PTFE:4.1.1 Type I and Type I
26、IResin produced from dispersion. Each type of resin has the same requirements for bulk density,particle size, water content, melting peak temperature, tensile, and elongation. Each type of resin is divided into grades inaccordance with standard specific gravity (SSG), Thermal Stability Index (TII),
27、and Stretching Void Index (SVI). Grades aredivided into classes according to extrusion pressure.NOTE 2See Tables 1 and 2 for details about grades and classes.4 Available from American National Standards Institute (ANSI), 25 W. 43rd St., 4th Floor, New York, NY 10036, http:/www.ansi.org.TABLE 1 Detai
28、l Requirements for all Types,A Grades and ClassesType Bulk Density,g/LParticle SizeAverageDiameter, mWater Content,max, %Melting PeakTemperature, C Tensile Strength,min, MPa Elongation at Break,min, %Initial SecondI 550 150 500 200 0.04 B 327 10 19 200II 550 150 1050 350 0.04 B 327 10 19 200AThe typ
29、es, grades, and classes are not the same as those in previous editions of Specification D4895.BGreater than 5.0C above the second melting peak temperature.D4895 1824.2 A line callout system is used to specify materials in this specification. The system uses predefined cells to refer to specificaspec
30、ts of this specification, as illustrated as follows:SpecificationStandard NumberBlockType Grade Class Special Notes| | | | |Example: Specification I 2 CD4895 - XXFor this example, the line callout would be Specification D4895 - XX, I2C, and would specify a coagulated dispersion form ofpolytetrafluor
31、oethylene that has all of the properties listed for that type, grade, and class in the appropriate specified properties ortables, or both, in the specification identified. A comma is used as the separator between the standard number and the type.Separators are not needed between the type, grade, and
32、 class.55. Mechanical Properties5.1 The resins covered by this specification shall be in accordance with the requirements prescribed in Tables 1 and 2, whentested by the procedures specified herein.6. Other Requirements6.1 The resin shall be uniform and shall contain no additives or foreign material
33、.6.2 The color of the material as shipped by the supplier shall be natural white.6.3 For purposes of determining conformance, all specified limits for this classification system are absolute limits, as definedin Practice E29.6.3.1 With the absolute method, an observed value is not rounded, but is to
34、 be compared directly with the limiting value.Example: In Table 2 Type I, Grade 4, Class B, under Specific Gravity, 2.14 shall be considered as 2.140000 and 2.16 shall beconsidered 2.160000.7. Sampling7.1 Sampling shall be statistically adequate to satisfy the requirements in Section 11.8. Number of
35、 Tests8.1 Lot inspection shall include tests for bulk density, particle size, and extrusion pressure. Periodic tests shall consist of all thetests specified in Tables 1 and 2 and shall be made at least once per year.5 See the Form and Style for ASTM Standards manual, available from ASTM Headquarters
36、.TABLE 2 Detail Requirements for All Types,A Grades and ClassesType Grade Class Standard Specific Gravity Extrusion Pressure, MPa Thermal Instability Index,max Stretching Void Index,maxmin maxI 1 A 2.14 2.18 5 to 15B 50 NACB 2.14 2.18 15 to 55D 50 NACC 2.14 2.18 15 to 75E 50 NAC2 A 2.17 2.25 5 to 15
37、B 50 NACB 2.17 2.25 15 to 55D 50 NACC 2.17 2.25 15 to 75E 50 NAC3 C 2.15 2.19 15 to 75E 15 200D 2.15 2.19 15 to 65E 15 100E 2.15 2.19 15 to 65E 50 2004 B 2.14 2.16 15 to 55D 15 50II 1 A 2.14 2.25 5 to 15B 50 NACAThe types, grades, and classes are not the same as those in previous editions of Specifi
38、cation D4895.BTested at a reduction ratio of 100:1 (reduction ratio is the ratio of the cross-sectional area of the preform to the cross-sectional area of the die).CNot applicable.DTested at a reduction ratio of 400:1.ETested at a reduction ratio of 1600:1.D4895 1838.2 The tests listed in Tables 1 a
39、nd 2, as they apply, are sufficient to establish conformity of a material to this specification. Oneset of test specimens as prescribed in Section 9 shall be considered sufficient for testing each sample. The average of the resultsfor the specimens tested shall conform to the requirements of this sp
40、ecification.9. Specimen Preparation9.1 Test Disks for Tensile Properties:9.1.1 Use the die shown in Fig. 1 for the molding of test disks (see Note 2). Place flat aluminum disks, 0.1 to 0.4 mm (0.004in. to 0.016 in.) thick and 76 mm (3 in.) in diameter, on both sides of the resin. The test resin shal
41、l be near ambient temperatureprior to molding (see Note 3). (WarningPTFE resins can evolve small quantities of gaseous products when heated above 204C(400F). Some of these gases are harmful. Consequently, exhaust ventilation must be used whenever these resins are heated abovethis temperature, as the
42、y are during the sintering operations that are a part of this specification. Since the temperature of burningtobacco exceeds 204C (400F), those working with PTFE resins shall ensure that tobacco is not contaminated.)NOTE 3For maximum precision, these weighing and preforming operations shall be carri
43、ed out at 23 6 2C (73.4 6 3.6F) (the “near ambient”temperature referred to herein). These operations shall not be performed at temperatures below 21C (70F) due to the crystalline transition that occursin PTFE in this temperature region which leads to possible cracks in sintered specimens and differe
44、nces in specimen density (as well as changes in otherphysical properties). Problems caused by the effect of temperature on the specific gravity or density of PTFE shall be minimized when the measurementis made using immersion procedures if a sensitive thermometer (for example, one reading 6 0.1C) is
45、 used in the liquid and the temperature is adjustedto be at least 22C.9.1.2 Screen 14.5 g of PTFE resin through a No. 10 sieve into the die. Adjust the lower plug height to allow the resin in thedie can be leveled by drawing a straightedge in contact with the top of the die across the top of the die
46、 cavity. Insert the die ina suitable hydraulic press and apply pressure gradually (see Note 4) until a pressure of 14 MPa (2030 psi) is attained. Hold thispressure for 3 min. Remove the disk from the die. Write the sample identification number on the preform using an appropriatemarker that will not
47、affect the PTFE during sintering.NOTE 4As a guide, increasing the pressure at a rate of 3.5 MPa (500 psi)/min is suggested until the desired maximum pressure is attained.9.1.3 Place the sintering oven in a laboratory hood (or equip it with an adequate exhaust system) and sinter the preforms inaccord
48、ance with Table 3, Procedure A (see Note 5).NOTE 5Although the rate of heat application is not critical, the cooling cycle is most important and the conditions cited in this procedure must befollowed very closely. If they are not followed, the crystallinity of the disks and the resulting physical pr
49、operties will be markedly changed. Therefore,NOTE 1All dimensions are in millimetres.FIG. 1 Mold Assembly for the Preparation of Specimens for the Determination of Tensile PropertiesD4895 184the use of a programmed oven is recommended for the most precise sintering cycle control and the hood window shall be left down during the entiresintering procedure, the latter being an important safety consideration.9.2 Test Specimens for Standard Specific Gravity and Thermal Instability Index:9.2.1 A cylindrical preforming mold, 29-mm (1
