1、Designation: D4895 10D4895 15Standard 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、dry-powder resins of polytetrafluoroethylene (PTFE) that have been prepared from dispersionsof PTFE by manufacturing techniques that involve controlled prepared by coagulation of the dispersion. These resins are generallyknown as “fine-powder” resins or “coagulated-dispersion powder” resins. The con
4、version of these resins to finished productsnormally involves a process called “paste extrusion,” and sometimes involves formative processes such as calendering. A volatileliquid is present as a processing aid during these formative stages of conversion, and is subsequently removed during the finish
5、ingstages of conversion. These PTFE resins are homopolymers of tetrafluoroethylene, or, in some cases, tetrafluoroethylene ormodified homopolymers containing not more than 1 % by weight of other fluoromonomers. The usual methods of processingthermoplastics generally are not applicable to these mater
6、ials because of their viscoelastic properties. The materials materialscovered herein do not include mixtures of PTFE with additives such as colors, fillers, or plasticizers; nor do they includereprocessed or reground resin or any fabricated articles because the properties of such materials have been
7、 irreversibly changedwhen they were fibrillated or sintered. The methods and properties included are those required to identify the various resins. Anadditional procedure is provided in the appendix for further characterization of the resins.1.2 The values stated in SI units as detailed in IEEE/ASTM
8、 SI-10 are to be regarded 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 addre
9、ss all of the safety 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.
10、NOTE 1Information in this specification is technically equivalent to related information in ISO 12086-1 and ISO 12086-2.2. Referenced Documents2.1 ASTM Standards:3D618 Practice for Conditioning Plastics for TestingD638 Test Method for Tensile Properties of PlasticsD792 Test Methods for Density and S
11、pecific Gravity (Relative Density) of Plastics by DisplacementD883 Terminology Relating to PlasticsD1895 Test Methods for Apparent Density, Bulk Factor, and Pourability of Plastic MaterialsD3892 Practice for Packaging/Packing of PlasticsD4052 Test Method for Density, Relative Density, and API Gravit
12、y of Liquids by Digital Density MeterD4441 Specification for Aqueous Dispersions of PolytetrafluoroethyleneD4591 Test Method for Determining Temperatures and Heats of Transitions of Fluoropolymers by Differential ScanningCalorimetryD4894 Specification for Polytetrafluoroethylene (PTFE) Granular Mold
13、ing and Ram Extrusion Materials1 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 July 1, 2010May 1, 2015. Published August 2010June 2015. Originally approved in
14、1989. Last previous edition approved in 20042010 asD4895 - 04.D4895 - 10. DOI: 10.1520/D4895-10.10.1520/D4895-15.2 Specifications for other forms of polytetrafluoroethylene are found in Specifications D4441 and D4894.3 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM
15、 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 indication of what changes have been made
16、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 considered the official document.*A Sum
17、mary 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 States1E11 Specification for Woven Wire Test Sieve Cloth and Test SievesE29 Practice for Using Significant Digits in Test Data to Dete
18、rmine Conformance with SpecificationsE177 Practice for Use of the Terms Precision and Bias in ASTM Test MethodsIEEE/ASTM SI-10 Use of the International System of Units (SI): The Modern Metric System2.2 ISO Standards:4ISO 12086-1 Plastics Fluoropolymer Dispersions and Molding and Extrusion MaterialsP
19、art 1: Designation and SpecificationISO 12086-2 Plastics Fluoropolymer Dispersions and Molding and Extrusion MaterialsPart 2: Preparation of Test Specimensand Determination of PropertiesISO 13322-2 Particle size analysisImage analysis methodsPart 2: Dynamic image analysis methods3. Terminology3.1 De
20、finitionsThe 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 grams per litre of resin measured under the conditions of the test.3.2.2 extended specific gravity (ESG), nthe specific gravity
21、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 measurement of SSG(see 3.2.8), using the appropriate sintering schedule given in this specification.3.2.3 lot, none production run o
22、r 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, that is capable of being handled. Molding and compaction are terms used interchangeably with preforming for PTFE.3.2.5 reground
23、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 that has been preformed and sintered.3.2.7 sintering, nas it applies to PTFE, a thermal treatment during which the PTFE is melted an
24、d recrystallized by coolingwith coalescence occurring during the treatment.3.2.8 standard specific gravity (SSG), nthe specific gravity of a specimen of PTFE material molded as described in thisspecification and sintered using the appropriate sintering schedule given in this specification.3.2.9 stra
25、ined specific gravity (strained SG), nthe specific gravity of a specimen of PTFE material molded, sintered, andstrained as described in this specification.3.2.10 stretching void index (SVI), na measure of the change in specific gravity of PTFE material which has been subjectedto tensile strain as de
26、scribed 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 period of time.3.2.12 unstrained specific gravity (USG), nthe specific gravity, prior to straining, of a specimen of PTFE materia
27、l 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 IIResin produced from dispersion and normally used with a volatile processing aid. dispersion. Eachtype of resin has the same requ
28、irements for bulk density, particle size, water content, melting peak temperature, tensile, andelongation. Each type of resin is divided into grades in accordance with standard specific gravity (SSG), Thermal Stability Index(TII), and Stretching Void Index (SVI). Grades are divided into classes acco
29、rding 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 Detail Requirements for all Types,A Grades and ClassesType Bulk Density,g
30、/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 200A TheThe types, grades, and classes are not the same as those in previous ed
31、itions of Specification D4895.B GreaterGreater than 5.0C above the second melting peak temperature.D4895 1524.2 A line callout system is used to specify materials in this specification. The system uses predefined cells to refer to specificaspects of this specification, as illustrated as follows:Spec
32、ificationStandard 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 ofpolytetrafluoroethylene that has all of the properties listed for that
33、 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 class.55. Mechanical Properties5.1 The resins covered b
34、y 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.6.2 The color of the material as shipped by the supplie
35、r 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 be compared directly with the limiting value.Example: I
36、n 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 Tests8.1 Lot inspection shall include tests for bulk de
37、nsity, 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 ASTM Form and Style Manual,for ASTM Standards manual, available from ASTM Headquarters.TABLE 2 Detail Requirements for All Types,A
38、 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 15B 50 NACB 2.17 2.25 15 to 55D 50 NACC 2.17 2
39、.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 NACA TheThe types, grades, and classes are not the same as those in previous editions of Specification D4895.B TestedTested at a reducti
40、on 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).C NotNot applicable.D TestedTested at a reduction ratio of 400:1.E TestedTested at a reduction ratio of 1600:1.D4895 1538.2 The tests listed in Tables 1 and 2, as they a
41、pply, 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 specification.9.
42、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 shall be near ambie
43、nt 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 they are during th
44、e 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 carried out at 23 6
45、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 differences in specime
46、n 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 used in the li
47、quid 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 cavity. Insert
48、 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 effectaffect th
49、e 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 inaccordance 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 cr
