1、Designation: D 4745 08Standard Specification forFilled Compounds of Polytetrafluoroethylene (PTFE)Molding and Extrusion Materials1This standard is issued under the fixed designation D 4745; the number immediately following the designation indicates the year oforiginal adoption or, in the case of rev
2、ision, 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 polytetrafluoroethylene(PTFE) filled molding compounds made with virgin
3、PTFEresins defined in Specification D 4894, as Types II and III.NOTE 1This specification can be used as a model for other PTFEcompounds having particulate fillers that can survive the sinteringtemperatures of PTFE as can those listed in this specification. Thisspecification is restricted to virgin P
4、TFE base resin for technical reasons.Recycled or reprocessed material cannot be processed successfully.NOTE 2The properties measured on commercially fabricated partsmay differ from the listed values for samples prepared by the proceduresgiven in this specification, depending on part geometry and pro
5、cessingparameters.NOTE 3There is no ISO equivalent to this specification.1.2 The values stated in SI units are to be regarded asstandard.1.3 The following statement applies to the test methodportion, Section 12, of this specification: This standard doesnot purport to address all of the safety concer
6、ns, if any,associated with its use. It is the responsibility of the user of thisstandard to establish appropriate safety and health practicesand determine the applicability of regulatory limitations priorto use. See Note 5 for a specific warning statement.2. Referenced Documents2.1 ASTM Standards:2D
7、 618 Practice for Conditioning Plastics for TestingD 638 Test Method for Tensile Properties of PlasticsD 792 Test Methods for Density and Specific Gravity (Rela-tive Density) of Plastics by DisplacementD 883 Terminology Relating to PlasticsD 1600 Terminology for Abbreviated Terms Relating toPlastics
8、D 3892 Practice for Packaging/Packing of PlasticsD 4894 Specification for Polytetrafluoroethylene (PTFE)Granular Molding and Ram Extrusion MaterialsIEEE/ASTM SI-10 Standard for Use of the InternationalSystem of Units (SI): The Modern Metric System33. Terminology3.1 DefinitionsThe terminology given i
9、n TerminologyD 883 is applicable to this specification unless otherwisespecified.3.2 Definitions of Terms Specific to This Standard:3.2.1 bulk density, nthe mass in kilograms per cubicmetre of resin compound measured under the conditions of thetest.3.2.2 filled compound, nblend of PTFE resin as the
10、matrixand particulate fillers, generally glass, other inorganic, metal-lic, or polymeric materials that withstand the sintering tem-perature of PTFE (327 to 380C).3.2.3 free-flow resins (pelletized), ngenerally made bytreatment of finely divided resins to produce free-flowingagglomerates.3.2.4 lot,
11、none production run or a uniform blend of twoor more production runs.3.2.5 pigmented compound, na compound in which apigment is added for colorant purposes only.3.2.6 standard flow resins (nonpelletized), nfinely dividedresin with an average particle size less than 100 m.3.3 AbbreviationsAbbreviatio
12、ns are in accordance withTerminology D 1600. PTFE is the acronym for polytetrafluo-roethylene.4. Classification4.1 This specification covers the following two types ofPTFE compounds:4.1.1 Type IStandard flow resins (nonpelletized) material,for general-purpose compression molding.4.1.2 Type IIFree-fl
13、ow resins (pelletized) material, forcompression molding, automatic molding, or ram extrusion.1This specification is under the jurisdiction of ASTM Committee D20 onPlastics and is the direct responsibility of Subcommittee D20.15 on ThermoplasticMaterials.Current edition approved Nov. 1, 2008. Publish
14、ed December 2008. Originallyapproved in 1991. Last previous edition approved in 2006 as D 4745 - 06.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Do
15、cument Summary page onthe ASTM website.3Available from ASTM International Headquarters, 100 Barr Harbor Drive,West Conshohocken, PA 194281*A Summary of Changes section appears at the end of this standard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-29
16、59, United States.4.2 Grades of each type distinguished by the nature of thefiller(s) are listed in Tables 1 and 2.4.3 A one-line system is used to specify materials coveredby this specification. The system uses predefined cells to referto specific aspects of this specification, as the followingillu
17、strates:SpecificationStandard Number : Type : Grade : Class : SpecialBlock : : : : Notes: :Example: SpecificationD474508II 24.3.1 For this example, the line callout would be Specifica-tion D 4745 08, Type II, Grade 2, and would specify afree-flowing (pelletized) composition of polytetrafluoroethyl-e
18、ne that has all of the properties listed for that type, and gradein the appropriate specified properties, tables, or both, in thespecification identified. A comma is used as the separatorbetween the standard number and the type. Separators are notneeded between the type, grade, and class.4A provisio
19、n forspecial notes is included so that other information can beprovided when required. Precede special notes, when used, bya comma.5. Ordering Information5.1 The filled compounds of PTFE are ordered using thetype, (see 4.1) and the grade (see reference Table 1), or they areordered using the designat
20、ion of the suppliers.6. Requirements6.1 The PTFE compounds covered by this specificationshall be uniform (filler and resin particles evenly distributed)and shall contain no foreign material.6.2 The PTFE compounds shall conform to the require-ments prescribed in Tables 1 and 2 when tested by theproce
21、dures specified herein. Table 1 lists requirements for TypeI. Table 2 references requirements for Type II.7. Sampling7.1 Sampling shall be statistically adequate to satisfy therequirements of 13.4.8. Number of Tests8.1 Routine lot inspection tests shall consist of those carriedout to determine the r
22、equirements specified in Table 1 depend-ing on type.8.2 The requirements listed in Tables 1 and 2, as they apply,are sufficient to establish conformity of a material to thisspecification. When the number of test specimens is not statedin the test method, single determinations may be made. If moretha
23、n single determinations are made on specimens fromseparate portions of the same sample, the results shall beaveraged. The single or average result shall conform to therequirements prescribed in this specification.9. Test Specimens9.1 Test specimens shall cut from a billet molded in accor-dance with
24、the following procedures. An acceptable alternateprocedure for molding a test plaque is described in Specifica-tion D 4894, subsection 9.1.1.9.2 Test Billets:9.2.1 Prior to molding, screen the material through a2.0-mm hand sieve, if necessary.9.2.2 Preform solid test billets in a mold (see Fig. 1) h
25、avinga cross-sectional area not greater than 25.8 cm2# (4 in.2) andof sufficient height to contain the sample. End plug clearanceshall be sufficient to ensure escape of entrapped air duringpressing. It is acceptable to vary the powder charge weight inaccordance with the density of the material. A mo
26、ld length of250 mm (9.8 in.) produces a billet approximately 75 mm (2 to3 in.) long. Powder-charge weight may be varied in accordancewith the density of the material. The billet length shall notexceed 75 mm (3 in.).9.2.3 Assemble the mold. Add the resin to the mold. Insertthe top plug and apply hand
27、 pressure, making certain that thepusher is centered in the mold. Place the mold in a hydraulicpress and remove the support ring or spacers. Increase theloading smoothly to the final preforming pressure in 3 to 5 min.4See the ASTM Form and Style Manual, available from ASTM Headquarters.TABLE 1 TFE C
28、ompounds, Type I, Standard Flow (Nonpelletized)Raw ResinBulk Density,min, g/LMolded Parts (Molded and Sintered)GradeSpecific Gravity,minSpecific Gravity,maxTensile StrengthElongation, min,%min, MPa min, psi1 15 % glass fiber 400 2.150 2.250 19.6 2840 2202 25 % glass fiber 425 2.150 2.250 15.7 2270 1
29、803 35 % glass fiber 350 2.200 2.300 10.3 1500 1504 5 % glass fiber and 5 % MoS2300 2.150 2.300 13.8 2000 2005 15 % glass fiber and 5 % MoS2375 2.150 2.300 13.8 2000 1506 10 % graphite 350 2.100 2.220 17.9 2600 1207 15 % graphite 300 2.100 2.200 13.8 2000 1008 25 % carbon and graphite 350 1.950 2.15
30、0 9.6 1400 209 32 % carbon and graphite 250 1.900 2.100 6.9 1000 2010 40 % bronze 500 2.950 3.350 16.5 2400 10011 60 % bronze 650 3.850 4.154 12.4 1800 5012 55 % bronze and 5 % MoS2700 3.500 4.000 10.3 1500 8013 50 % stainless steel 500 3.200 3.600 15.2 2200 1200 As specified by customer andsupplier
31、As specified by customer and supplier.D4745082Use 20.7 MPa (3000 psi) for compounds containing up to 4 %by weight filler. Use 34.5 MPa (5000 psi) for compoundscontaining 5 to 25 % by weight and 68.9 MPa (10 000 psi) forcompounds containing more than 26 % filler. Hold undermaximum pressure for 2 to 5
32、 min. Open the press, remove thetop pusher from the mold, and force the preform vertically outof the mold, using a continuous, smooth movement.9.2.4 Place the preform in a sintering oven and sinter inaccordance with the procedure in Table 3.9.2.5 Safety WarningAt normal processing temperatures,PTFE
33、liberates harmful vapors. Provide adequate ventilation inareas where PTFE compounds are exposed to elevated tem-peratures. Avoid contaminating smoking materials with PTFEcompounds.9.3 Sectioning Test Billet:9.3.1 Divide the test billet into sections by making trans-verse cuts by machining, or by a s
34、uitable alternate procedure,in accordance with Fig. 2.9.3.2 Prepare five test specimens, 1 6 0.25 mm (0.040 60.010 in.) in thickness for the determination of tensile strengthand elongation and cut a piece of suitable thickness for specificTABLE 2 TFE Compounds, Type II, Free-Flow (Pelletized)Raw Res
35、inBulk Density,min, g/LMolded Parts (Molded and Sintered)GradeSpecific Gravity,minSpecific Gravity,maxTensile StrengthElongation, min,%min, MPa min, psi1 15 % glass fiber 625 2.150 2.25 13.8 2000 2002 25 % glass fiber 625 2.150 2.250 12.4 1800 1503 35 % glass fiber 650 2.150 2.250 8.3 1200 1004 5 %
36、glass fiber and 5 % MoS2575 2.150 2.300 17.2 2500 1705 15 % glass fiber and 5 % MoS2600 2.150 2.300 13.8 1800 1206 10 % graphite 600 2.070 2.190 13.8 2000 1507 15 % graphite 550 2.100 2.200 10.3 1500 608 25 % carbon and graphite 500 1.950 2.100 8.3 1200 209 32 % carbon and graphite 400 1.900 2.200 6
37、.9 1000 2010 40 % bronze 750 2.950 3.250 13.8 2000 8511 60 % bronze 900 3.800 4.000 10.3 1500 2012 55 % bronze and 5 % MoS2900 3.500 4.000 6.9 1000 2013 50 % stainless steel 850 3.200 3.600 13.8 2000 1000 As specified by customer andsupplierAs specified by customer and supplier.FIG. 1 Preforming of
38、PTFE Composite Test BilletTABLE 3 Sintering Procedures for Test BilletsInitial temperature, C (6)AAmbientRate of heating, C/h (F/h) 60 6 5 (108 6 9)Hold temperature, C (F) 370 6 6 (698 6 10)Hold time, min 240 6 5Rate of cooling, C/h (F/h) 60 6 5 (1086 9)Final temperature, C (F)A95 6 6 (2036 10)AOven
39、 can be opened safely at these temperatures.FIG. 2 Sectioned PTFE Test BilletD4745083gravity measurements. This piece will be approximately cubi-cal in shape, weighing at least 10 g. All surfaces must besmooth. Take care to avoid wedge-shape cuts. Alternate mold-ing for specific gravity specimens as
40、 described in D 4894,subsection 9.2.1 and Appendix X1.10. Conditioning Test Specimens10.1 For density and tensile properties the test specimensshall be conditioned in accordance with Procedure A ofPractice D 618 for a period of at least 4 h prior to test.11. Test Conditions11.1 Tests shall be conduc
41、ted at 23 6 2C (73.4 6 4F).Since the resin does not absorb water, the maintenance ofconstant humidity during testing is not required.12. Test Methods12.1 Filler Content:12.1.1 ScopeThis burn-out procedure for filler contentmay be used for determining the amount of a filler in acompound. The entire p
42、rocedure shall be carried out in an inertatmosphere, especially when fillers that react with PTFE andoxygen are present. Reaction with oxygen produces volatileproducts that will cause incorrect results. This procedure is notsuitable for use with fillers that are not thermally stable at themaximum te
43、mperature of the method.12.1.2 The equipment used is a tube furnace suitable for useat 680 6 25C (1250 6 50F). The furnace shall have acombustion tube and combustion boats made of materialssuitable to withstand reactive decomposition gases.Asystem isneeded to supply a constant purge of dry nitrogen,
44、 or suitablepurge gas, through the furnace at a rate of 10 to 50 mL/min.12.1.3 Scrub the pyrolysis gases with a base, such as a dilutesolution of sodium hydroxide, and vent to the outside atmo-sphere.NOTE 4Vycor glass or ceramic is recommended for the combustiontube. Nickel or platinum is recommende
45、d for the combustion boats.NOTE 5Take care to avoid leakage of fumes into the work area. Takeprecautions to avoid the inhalation of, or exposure to gases from thepyrolysis since these gases may be hazardous.12.1.4 Add approximately2gofthesample to each of thecombustion boats, using standard quantita
46、tive laboratoryweighing practices. Place boats containing the samples into thefurnace. Heat and hold at 680 6 25C (1250 6 50F) untilcomplete degradation of the PTFE has occurred. One hour atmaximum temperature is typically sufficient. Calculate thepercentage of filler as the net weight of the residu
47、e multipliedby 100, divided by the net weight of the original sample.12.2 Filler Content (Alternate Method):12.2.1 EquipmentThermogravimetric analyzer, capableof weighing a sample as heat is applied. The analyzer shall beprogrammable to heat at a predetermined rate and hold at amaximum temperature o
48、f at least 680 6 25C (1250 6 50F).A constant supply of nitrogen, or suitable purge gas, is neededto flow through the furnace. Follow the manufacturers instruc-tions for recommended flow rates. The crucible shall beconstructed of aluminum oxide or platinum.12.2.2 The pyrolysis gases shall be scrubbed
49、 in accordancewith 12.1.3.12.2.3 Add 50 6 10 mg to a crucible. Place crucible andsample in furnace. Ensure purge gas is flowing through thesystem at the recommended rate. Program the analyzer to heatat 20C 6 1C (68F 6 1.8F). Hold at 680 6 25C (1250 650F) until complete degradation of the PTFE has occurred.The analyzer shall be capable of calculating the residue leftafter the test cycle is complete. Follow the manufacturersinstructions.12.3 Bulk Density:12.3.1 Perform the test in accordance with instructions titledbulk density in Specifi
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