1、Designation: D4894 07 (Reapproved 2012)D4894 15Standard Specification forPolytetrafluoroethylene (PTFE) Granular Molding and RamExtrusion Materials 1This standard is issued under the fixed designation D4894; the number immediately following the designation indicates the year oforiginal adoption or,
2、in the case of revision, the year 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.1. Scope*1.1 This specification covers granular resins and test methods for polytetrafluoroet
3、hylene (PTFE) that have never beenpreformed or molded and are normally processed by methods similar to those used in powder metallurgy or ceramics, or by specialextrusion processes. These PTFE resins are homopolymers of tetrafluoroethylene, or, in some cases, modified homopolymerscontaining not more
4、 than one percent by weight of other fluoromonomers. The usual methods of processing thermoplasticsgenerally are not applicable to these materials because of their viscoelastic properties at processing temperatures. The materialsincluded herein do not include mixtures of PTFE resin with additives su
5、ch as colorants, fillers or plasticizers; nor do they includereprocessed or reground resin or any fabricated articles. The methods and properties included are those required to identify thevarious types of resins. Additional procedures are provided in the Appendix for further characterization of the
6、 resins.1.2 The values stated in SI units as detailed in IEEE/ASTM SI-10 are to be regarded as the standard, and the practices ofIEEE/ASTM SI-10 are incorporated herein.1.3 The following precautionary caveat pertains only to the Specimen Preparation section, Section 9, and the Test Methodssection, S
7、ection 10, of this specification: This specification does not purport to address 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 limitat
8、ions prior to use. See Notes 3 and 9 for specific cautionary statements.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:2D618 Practice for Conditioning Plastics for TestingD638 Test Meth
9、od for Tensile Properties of PlasticsD792 Test Methods 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, Bul
10、k Factor, and Pourability of Plastic MaterialsD3295 Specification for PTFE Tubing, Miniature Beading and Spiral Cut TubingD3892 Practice for Packaging/Packing of PlasticsD4441 Specification for Aqueous Dispersions of PolytetrafluoroethyleneD4591 Test Method for Determining Temperatures and Heats of
11、Transitions of Fluoropolymers by Differential ScanningCalorimetryD4745 Classification System and Basis for Specification for Filled Polytetrafluoroethlyene (PTFE) Molding and ExtrusionMaterials Using ASTM MethodsD4895 Specification for Polytetrafluoroethylene (PTFE) Resin Produced From DispersionE11
12、 Specification for Woven Wire Test Sieve Cloth and Test SievesE177 Practice for Use of the Terms Precision and Bias in ASTM Test MethodsIEEE/ASTM SI-10 Standard for Use of the International System of Units (SI): The Modern Metric System1 This specification is under the jurisdiction of ASTM Committee
13、 D20 on Plastics and is the direct responsibility of Subcommittee D20.15 on Thermoplastic Materials.Current edition approved April 1, 2012May 1, 2015. Published June 2012June 2015. Originally approved in 1989. Last previous edition approved in 20072012 asD4894 - 07.D4894 - 07(2012). DOI: 10.1520/D48
14、94-07R12.10.1520/D4894-15.2 For referencedASTM standards, visit 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 standa
15、rd and is intended only to provide the user of an ASTM 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
16、only the current versionof the standard as published by 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 States12.2 ISO Standards:
17、3ISO 12086-1 PlasticsFluoropolymer Dispersions and Moulding and Extrusion MaterialsPart 1: Designation System andBasis for SpecificationISO 12086-2 Test Methods for Fluoropolymers3. Terminology3.1 Definitions:3.1.1 The terminology given in Terminology D883 is applicable to this specification.3.2 Des
18、criptions of Terms Specific to This Standard:3.2.1 bulk densitythe mass (in grams) per litre of resin measured under the conditions of the test.3.2.2 extended specific gravity (ESG)the specific gravity of a specimen of PTFE material molded as described in thisspecification and sintered (g.v.) for an
19、 extended period of time, compared to the sintering time for the measurement of standardspecific gravity (SSG), 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 preformingcompacting powdered PT
20、FE material under pressure in a mold to produce a solid object, called a preform,that is capable of being handled. Molding and compaction are terms used interchangeably with preforming for PTFE.3.2.5 reground resinthat produced by grinding PTFE material that has been preformed but has never been sin
21、tered.3.2.6 reprocessed resinthat produced by grinding PTFE material that has been both preformed and sintered.3.2.7 sinteringas it applies to PTFE, a thermal treatment during which the PTFE is melted and recrystallized by cooling withcoalescence occurring during the treatment.3.2.8 skivinga machini
22、ng operation during which a continuous film of PTFE material is peeled from the lateral surface of acylindrical sintered molding.3.2.9 standard specific gravity (SSG)the specific gravity of a specimen of PTFE material molded as described in thisspecification and sintered using the appropriate sinter
23、ing schedule given in this specification.3.2.10 thermal instability index (TII)a measure of the decrease in molecular weight of PTFE material which has been heatedfor a prolonged period of time.4. Classification4.1 This specification covers the following six types of PTFE generally used for compress
24、ion molding or ram extrusion, or both:4.1.1 Type IResin used for general-purpose molding and ram extrusion.4.1.2 Type IIFinely divided resin with an average particle size less than 100 micrometres.4.1.3 Type IIIModified resins, either finely divided or free-flowing, typically used in applications re
25、quiring improvedresistance to creep and stress-relaxation in end-use.4.1.4 Type IVFree-flowing resins. Generally made by treatment of finely divided resin to produce free-flowing agglomerates.4.1.5 Type VPresintered. Resin that has been treated thermally at or above the melting point of the resin at
26、 atmosphericpressure without having been previously preformed.4.1.6 Type VIResin, not presintered, but for ram extrusion only.NOTE 2See Tables 1 and 2 for division of Types by Grades, and footnotes to Tables 1 and 2 (and Table X2.1 in Appendix X2.) for formerclassifications.3 Available from American
27、 National Standards Institute (ANSI), 25 W. 43rd St., 4th Floor, New York, NY 10036, http:/www.ansi.org.TABLE 1 Detail Requirements for Tests on ResinsAType Grade Bulk Density, g/L Particle Size, Average Diameter, m Water Content, max, % Melting Peak TemperatureInitial C Second CI 1 700 100 500 150
28、0.04 A 327 102 675 50 375 75 0.04 A 327 10II . . . . . . 800 . . . 0.04 A 327 103 580 80 200 75 0.04 A 327 10V . . . 635 100 500 250 0.04 327 10 327 10VI . . . 650 150 800 250 0.04 A 327 10A 5C above the second melting peak temperature.D4894 1524.2 Aline callout system is used to specify materials i
29、n this standard.The system uses predefined cells to refer to specific aspectsof this specification, illustrated as follows:SpecificationStandard Number Block : Type : Grade : Class : Special notes: : : : :Example: ASTMD4894 04 III 2For this example, the line callout would be ASTM D4894 04, III2, and
30、 would specify a granular polytetrafluoroethylene thathas all of the properties listed for that Type and Grade in the appropriate specified properties, Tables, or both, in this specification.In this case there is no Class item so the cell position for class is left blank. A comma is used as the sepa
31、rator between StandardNumber andType. Separators are not needed betweenType, Grade, and Class.4 Provision for Special Notes is included so that otherinformation will be provided when required. An example would be in Specification D3295 where dimensions and tolerances arespecified for each AWG size w
32、ithin 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 conform to the requirements prescribed in Tables 1 and 2 when tested by theprocedures specified herein. Table 1 lists tests to be carried ou
33、t on resins. Table 2 lists tests requiring specimens molded asdescribed in Section 9.6. 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 seller shall be white.7. Sampling7.1 Sampling shall be statistic
34、ally adequate to satisfy the requirements of 11.48. Number of Tests8.1 Lot inspection shall include tests for bulk density, particle size and standard specific gravity. Periodic tests shall consist ofall the tests specified in Tables 1 and 2 and shall be made at least one per year.8.2 The tests list
35、ed in Tables 1 and 2, as they apply, are sufficient to establish conformity of a material to this specification. Oneset of tests specimens as prescribed in Section 7 shall be considered sufficient for testing each sample. The average of the resultsfor the specimens tested shall conform to the requir
36、ements of this specification.9. Specimen Preparation9.1 Test Disks:9.1.1 Use the die shown in Fig. 1 for the molding of test disks. The test resin shall be near ambient temperature prior to molding(Note 5). WarningPTFE can evolve small quantities of gaseous products when heated above 204C (400F). So
37、me of thesegases are harmful. Consequently, exhaust ventilation must be used whenever the resins are heated above this temperature, as they4 See the ASTM Form and Style Manual,for ASTM Standards manual available from ASTM Headquarters.TABLE 2 Detail Requirements for Tests on Molded SpecimensType Gra
38、de Thermal Instability Index, max Standard Specific Gravity Tensile Strength, min Elongation at break min %min max MPa psiI 1 50 2.13 2.18 13.8 2000 1402 50 2.13 2.18 17.2 2500 200II . . . 50 2.13 2.19 27.6 4000 300III 1 50 2.14 2.22 28.0 4060 4502 50 2.14 2.18 20.7 3000 300IV 1 50 2.13 2.19 25.5 37
39、00 2752 50 2.13 2.19 27.6 4000 3003 50 2.15 2.18 27.6 4000 200V . . . NAA NAA NAA NAA NAA NAAVIB . . . NAA NAA NAA NAA NAA NAAA NA: Not Applicable by molding techniques included in this specification.B Extrusions of this resin show different degrees of clarity from the others.D4894 153are during the
40、 sintering operations that are a part of this specification. Since the temperature of burning tobacco exceeds 204C(400F), those working with PTFE resins should ensure that tobacco is not contaminated.9.1.2 Screen 14.5 g (for tensile properties) or 7.25 g (for electrical properties discussed in Appen
41、dix X1.7) of PTFE resinthrough a No. 10 hand sieve into the die. Adjust the lower plug height to allow the resin in the die can be leveled by drawing astraightedge in contact with the top of the die across the top of the die cavity. Insert the die in a suitable hydraulic press and applypressure grad
42、ually (Note 3) until a total of 34.5 MPa (5000 psi) is attained. Hold this pressure for 3 min. Remove the diskidentification on the disk at this time.NOTE 3As a guide, increasing the pressure at a rate of 3.45 MPa (500 psi)/min is suggested until the desired maximum pressure is attained.9.1.3 Sinter
43、 the preforms in accordance with Table 3 (Note 4).9.1.3.1 Use Procedure B for Types I, II and IV and Procedure C for Type III.NOTE 4Although the rate of heating application is not critical, the cooling cycle is most important and the conditions cited in these procedures mustbe followed very closely.
44、 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 so that the hood window will be left down during the entiresintering procedure,
45、 the latter being an important safety consideration.9.2 Test Specimens for Standard Specific Gravity (SSG) and Extended Specific Gravity (ESG):9.2.1 A cylindrical preforming die, 28.6 mm (118 in.) internal diameter by at least 76.2 mm (3 in.) deep, is used to prepare thepreforms. End plug clearances
46、 shall be sufficient to ensure escape of air during pressing. The test resin shall be near ambienttemperature prior to molding (Note 5).NOTE 5For maximum precision, the weighing and preforming operations shall be carried out at 23 6 2C (73.4 6 3.6F) (the “near ambient”temperature referred to herein)
47、. These operations shall not be preformed 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 properties). Problem
48、s caused by the effects of temperature on the specific gravity or density of PTFE will be minimized when the measurementis made using immersion procedures if a sensitive thermometer (for example, one reading 60.1C) is used in the liquid and the temperature is adjustedto be at least 22C.9.2.2 Weigh o
49、ut 12.0 6 0.1 g of resin and place it in the die. Screen non-free-flowing resins through a No. 10 sieve. Break upcompacted resins by hand-shaking cold resin in a half-filled sealed glass container. Condition the resin in the sealed glass containerin a freezer or dry-ice chest. After breaking up resin lumps, allow the sealed container to equilibrate to near ambient temperature.Then screen and weigh the 12.0 6 0.1-g sample. Insert the die in a suitable hydraulic press and apply pressure gradually (Note3) u
