1、Designation: D4895 15D4895 16Standard 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 thea dispersion. These PTFE resinsare homopolymers of tetrafluoroethylene or modified homopolymers containing not more than 1 % by weight of otherfluoromonomers. The materials covered herein do not include mixtures of PTFE with additives such
4、 as colors, fillers, orplasticizers; nor do they include reprocessed or reground resin or any fabricated articles because the properties of such materialshave been irreversibly changed when they were fibrillated or sintered.1.2 The values stated in SI units as detailed in IEEE/ASTM SI-10 are to be r
5、egarded 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 safe
6、ty 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
7、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 Specific Gravity (R
8、elative 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 MaterialsD3892 Practice for Packaging/Packing of Plas
9、ticsD4052 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 Fluoropolymers by Differential ScanningCalorimetryD
10、4894 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 SpecificationsE177 Practice for Use of the Terms Pre
11、cision 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 MaterialsPart 1: Designation and Specification1 This specification is under the juris
12、diction of ASTM Committee D20 on Plastics and is the direct responsibility of Subcommittee D20.15 on Thermoplastic Materials.Current edition approved May 1, 2015May 1, 2016. Published June 2015May 2016. Originally approved in 1989. Last previous edition approved in 20102015 asD4895 - 10.D4895 - 15.
13、DOI: 10.1520/D4895-15.10.1520/D4895-16.2 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 Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvol
14、ume information, refer to the standards Document Summary page on the ASTM website.4 Available from American National Standards Institute (ANSI), 25 W. 43rd St., 4th Floor, New York, NY 10036, http:/www.ansi.org.This document is not an ASTM standard and is intended only to provide the user of an ASTM
15、 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 current versionof the standard as published b
16、y ASTM is 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 States1ISO 12086-2 Plastics Fluoropolymer Dispersions and Molding and Extrusion
17、 MaterialsPart 2: Preparation of Test Specimensand Determination 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 T
18、erms 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 of a specimen of PTFE material molded as described in thisspecification and sintered (see 3.2.7) for an exte
19、nded 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 or a uniform blend of two or more production runs.3.2.4 preforming, vbcompacting powdered PTFE material under
20、 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 resin, nresin produced by grinding PTFE material that has been preformed but has never been sintered.3.2.6 r
21、eprocessed 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 and recrystallized by coolingwith coalescence occurring during the treatment.3.2.8 standard specific gravity (
22、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 strained specific gravity (strained SG), nthe specific gravity of a specimen of PTFE material molded, sintered,
23、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 described in this specification.3.2.11 thermal instability index (TII), na measure of the decrease in molecula
24、r 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 material used in theStretching Void Index Test (see 10.9) of this specification.4. Classification4.1 This specifica
25、tion covers the following types of PTFE:4.1.1 Type I and Type IIResin 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 s
26、tandard specific gravity (SSG), Thermal Stability Index (TII), 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.4.2 A line callout system is used to specify materials in this specification. T
27、he system uses predefined cells to refer to specificaspects of this specification, as illustrated as follows:SpecificationStandard NumberBlockType Grade Class Special Notes| | | | |Example: Specification I 2 CD4895 - XXTABLE 1 Detail Requirements for all Types,A Grades and ClassesType Bulk Density,g
28、/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 types, grades, and classes are not the same as those in previous editio
29、ns of Specification D4895.BGreater than 5.0C above the second melting peak temperature.D4895 162For 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 type, gra
30、de, 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 by this spe
31、cification 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 supplier shall be
32、 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: In Table 2
33、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 density, par
34、ticle 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.8.2 The tests listed in Tables 1 and 2, as they apply, are sufficient to establish conformity of a material to this specification. Oneset of test spec
35、imens 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. Specimen Preparation9.1 Test Disks for Tensile Properties:9.1.1 Use the die shown in Fig. 1 for the m
36、olding 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 ambient temperatureprior to molding (see Note 3). (WarningPTFE resins can evolve small quantities of gaseo
37、us 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 the sintering operations that are a part of this specification. Since the temperature of burningtobacco
38、 exceeds 204C (400F), those working with PTFE resins shall ensure that tobacco is not contaminated.)5 See the Form and Style for ASTM Standards manual, available from ASTM Headquarters.TABLE 2 Detail Requirements for All Types,A Grades and ClassesType Grade Class Standard Specific Gravity Extrusion
39、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 2.25 15 to 75E 50 NAC3 C 2.15 2.19 15 to 75E 15 200D 2.15 2.19 15 to 65E
40、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 Specification D4895.BTested at a reduction ratio of 100:1 (reduction ratio is the ratio of the cross-sectional area of the
41、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 163NOTE 3For maximum precision, these weighing and preforming operations shall be carried out at 23 6 2C (73.4 6 3.6F) (the “near ambient”temperature ref
42、erred 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 specimen density (as well as changes in otherphysical prop
43、erties). 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 liquid and the temperature is adjustedto be at least
44、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 the die ina suitable hydraulic press and apply pre
45、ssure 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 affect the PTFE during sintering.NOTE 4As a guide, increasing the
46、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 rat
47、e of heat application is not critical, the cooling cycle is most important and the conditions cited in this procedure must beNOTE 1All dimensions are in millimetres.FIG. 1 Mold Assembly for the Preparation of Specimens for the Determination of Tensile PropertiesTABLE 3 Sintering ProceduresA BInitial
48、 temperature, C (F) 290 (554) 290 (554)Rate of heating, C/h (F/h) 120 10 120 10(216 18) (216 18)Hold temperature, C (F) 380 6 380 6(716 10) (716 10)Hold time, min 30 + 2, 0 360 5Cooling rate, C/h (F/h) 60 5 60 5(108 9) (108 9)Second hold temperature, C (F) 294 6 294 6(561 10) (561 10)Second hold tim
49、e, min 24 + 0.5, 0 24 + 0.5, 0Period to room temperature, min $30 $30D4895 164followed very closely. If they are not followed, the crystallinity of the disks and the resulting physical properties will be markedly changed. Therefore,the 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 Specif
