1、Designation: D7194 12Standard Specification forAerospace Parts Machined from Polychlorotrifluoroethylene(PCTFE)1This standard is issued under the fixed designation D7194; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of
2、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. Scope1.1 This specification is intended to be a means of callingout finished machined parts ready for aerospace use. Such parts
3、may also find use in selected commercial applications wherethere are clear benefits derived from the use of parts withknown or controlled crystallinity, high molecular weight, goodmolecular weight retention during processing, dimensionalstability in the finished part, and tightly controlled engineer
4、ingtolerances.1.2 This specification establishes requirements for partsmachined from virgin, unplasticized, 100 % polychlorotrifluo-roethylene (PCTFE) homopolymers.1.3 This specification does not cover parts machined fromPCTFE copolymers, PCTFE film or tape less than 0.25-mm(0.010-in.) thick, or mod
5、ified PCTFE (containing pigments orplasticizers).1.4 This specification does not allow parts containing re-cycled material.1.5 The specification does not cover PCTFE parts intendedfor general use applications, in which control of dimensionalstability, molecular weight, and crystallinity are not as i
6、mpor-tant. For machined PCTFE parts intended for general use, useSpecification D7211.1.6 This specification classifies parts into three classesbased upon intended uses and exposures: oxygen-containingmedia, reactive media, and inert media.1.7 ApplicationPCTFE components covered by this speci-ficatio
7、n are virgin, 100 % PCTFE resin, free of plasticizers andother additives. The components are combustion resistant inoxygen, dimensionally stable, and meet other specific physicalcharacteristics appropriate for their end use. They are used invalves, regulators, and other devices in oxygen, air, heliu
8、m,nitrogen, hydrogen, ammonia, and other aerospace mediasystems. The components typically are used as valve seats,o-rings, seals, and gaskets. They are removed and replacedduring normal maintenance procedures. The components pro-vide reliable sealing surfaces resulting in proper closure ofvalves and
9、 related devices and no leakage from the system intothe environment. They will experience static mechanicalloading, cyclic mechanical loading, temperatures ranging fromcryogenic to 71 C (160 F), and pressures up to 68.9 MPa(10,000, psig) for oxygen and air media, and 103.4 MPa(15,000 psig) for inert
10、 media.1.8 The values stated in SI units are to be regarded asstandard. The values in parentheses are for information only.1.9 The following precautionary caveat pertains only to thetest methods portion, Section 12, of this specification: Thisstandard does not purport to address all of the safety co
11、ncerns,if any, associated with its use. It is the responsibility of the userof this standard to establish appropriate safety and healthpractices and to determine the applicability of regulatorylimitations prior to use.NOTE 1There is no known ISO equivalent to this standard.2. Referenced Documents2.1
12、 ASTM Standards:2D618 Practice for Conditioning Plastics for TestingD638 Test Method for Tensile Properties of PlasticsD792 Test Methods for Density and Specific Gravity (Rela-tive Density) of Plastics by DisplacementD883 Terminology Relating to PlasticsD1430 Classification System for Polychlorotrif
13、luoroethylene(PCTFE) PlasticsD1600 Terminology forAbbreviated Terms Relating to Plas-ticsD1708 Test Method for Tensile Properties of Plastics by Useof Microtensile SpecimensD2512 Test Method for Compatibility of Materials withLiquid Oxygen (Impact Sensitivity Threshold and Pass-Fail Techniques)1This
14、 specification is under the jurisdiction of ASTM Committee D20 onPlastics and is the direct responsibility of Subcommittee D20.15 on ThermoplasticMaterials.Current edition approved Oct. 1, 2012. Published November 2012. Originallyapproved in 2005. Last previous edition approved in 2005 as D5111 - 05
15、. DOI:10.1520/D7194-12.2For 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 Document Summary page onthe ASTM website.Copyright ASTM International, 100 Barr
16、 Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1D4591 Test Method for Determining Temperatures andHeats of Transitions of Fluoropolymers by DifferentialScanning CalorimetryD7211 Specification for Parts Machined from Polychlorotri-fluoroethylene (PCTFE) and Intended for Ge
17、neral UseG86 Test Method for Determining Ignition Sensitivity ofMaterials to Mechanical Impact in Ambient Liquid Oxy-gen and Pressurized Liquid and Gaseous Oxygen Envi-ronments2.2 Federal Standards3NASA-STD-6001B Flammability, Offgassing, and Compat-ibility Requirements and Test ProceduresMechanical
18、Impact for Materials inAmbient Pressure LOX (Test 13A)and Mechanical Impact for Materials in Variable PressureGOX and LOX (Test 13B)3. Terminology3.1 Definitions:3.1.1 Terms are defined in accordance with TerminologiesD883 and D1600 unless otherwise indicated.3.1.2 air media, nliquid air, pressurize
19、d air, and breathingair.3.1.3 cognizant engineering organization, nthe company,agency, or other authority responsible for the system orcomponent in which aerospace grade PCTFE is used. This, inaddition to design personnel, may include personnel frommaterial and process engineering, or quality groups
20、 and othersas appropriate.3.1.4 inert media, ngaseous helium (GHe) and gaseousnitrogen (GN2) up to 103.4 MPa (15,000 psig).3.1.5 oxygen media, nliquid oxygen (LOX) and gaseousoxygen (GOX) up to 68.9 MPa (10,000 psig).3.1.6 processing route, nthe method whereby a thermo-plastic is taken above its mel
21、ting point and processed into asemifinished article, typically sheet or rod stock. For PCTFE,the common processing methods are extrusion and compres-sion molding.3.1.7 reactive media, nammonia (NH3) up to 3.5 MPa(500 psig), gaseous hydrogen (GH2) up to 46.2 MPa (6700psig), and liquid hydrogen (LH2)
22、up to 2.8 MPa (400 psig).4. Classification4.1 Part shape and size shall be defined by the applicablepurchase order.4.2 The type of product shall be categorized by the intendeduse category:4.2.1 Type I for use in air and oxygen media (see 3.1.2 and3.1.5) at service pressures above 11.4 MPa (1650 psi)
23、 thatrequire batch testing4.2.2 Type II for use in (1) air and oxygen media (at servicepressures below 11.4 MPa (1650 psi), or at service pressuresabove 11.4 MPa (1650 psi) that do not require batch testing);or (2) inert and reactive media up to the pressures specified in3.1.4 and 3.1.7.4.2.3 Type I
24、II for use in media other than air, oxygen, GHe,GN2, ammonia, GH2and LH2, at service pressures specified bythe cognizant engineering organization.5. Ordering Information5.1 All parts covered by this specification shall be orderedby Specification D7194, Type, as listed in Section 4, or as listedon th
25、e procurement drawing when Type is not specifiedexplicitly6. Materials and Manufacture6.1 Parts shall be made from as-polymerized resin meetingall requirements of Classification System D1430. Type I, II andIII parts shall be fabricated from as-polymerized resin classi-fied as meeting Classification
26、System D1430, Group 01, Class1, Grade 3.6.2 Parts shall be made from virgin, unplasticized, 100 %polychlorotrifluoroethylene (PCTFE) homopolymer.6.3 No recycled polymer or regrind shall be permitted.6.4 The base material shall be free of all defects or con-taminants that would be detrimental to fina
27、l fabrication orperformance of the finished parts.7. Property Requirements7.1 Specification values listed in this specification are mini-mum specification values. Any additional requirement forspecific tests or data shall be specified at the time of the order.8. General RequirementsNOTE 2Unless othe
28、rwise specified in the purchase contract or order,the molder producing the semifinished article from which finished partsare made will be responsible for insuring the requirements in 8.6 are met.All other requirements listed in Section 8 pertain to the finished part, andtherefore, will be the respon
29、sibility of the supplier of the finished,machined part.8.1 Finished parts shall have a natural translucent appear-ance. The color shall be white or gray with no yellowing orother unnatural color.8.2 Finished parts shall be free of voids, scratches, fissures,inclusions, or entrapped air bubbles that
30、will affect serviceabil-ity. No particles (for example, black specks) shall be visible tothe naked eye.8.3 All finished parts are to be supplied after being annealedin accordance with 12.4.8.4 No dimension of a finished part shall change more than0.003 mm/mm (0.003 in./in.) measured at 23 6 2C(736 4
31、F) before and after being held for 48 6 5hat716 5 C (1606 9 F), as determined by the method in 12.5.8.5 Finished parts shall be made from semifinished articleshaving a zero strength time (ZSTstock) of 300 to 450 s (Grade 3)when determined in accordance with 12.1.8.6 The maximum allowable ZST drop, Z
32、ST, shall be11.4 (1650):only partsfor whichmechanicalimpacttesting isrequiredoxygen, air yes yesII oxygen, air:11.4 (1650):only partsfor which nomechanicalimpacttesting isrequiredHe:inert, reactive:pressuresspecifiedin 3.1.4 and3.1.7:all partsoxygen, air,inert, reactiveno noIII all pressuresBand par
33、tsother(for example,nitrox)no noAFinished parts made from Type I, II and III material will be in an annealedcondition, have a ZSTstockfrom 300 to 450 s, and have a ZST drop no greater than20 %.BAs specified by the cognizant engineering organization.D7194 12312.3.3 Samples shall be prepared in accord
34、ance with TestMethod G86.12.3.4 Surface contamination shall be removed by filtered,gaseous nitrogen; or oxygen-compatible solvent, detergent anddistilled water, as appropriate.12.3.5 Pure GOX or LOX shall be used (choice depends onend-use application).12.3.6 Test conditions shall be at the ambient t
35、emperature ofthe test facility and a pressure of 11.4 MPa (1650 psi).12.3.7 Twenty separate samples shall be impacted at 98 J(72 lbf) using a 12.7-mm (12-in.) diameter contact.12.3.8 No advance reactions shall be observed. This in-cludes a single audible explosion, visual flash, burning orcharring o
36、f samples, or major discoloration.12.3.9 If any sample fails, 40 additional samples shall betested without any reactions.12.4 Annealing12.4.1 Method A (best dimensional stability) shall be thepreferred annealing method. However, in cases where itimperative to maintain closest tolerances, Method B sh
37、all bepreferred.12.4.2 The appropriate annealing method shall be chosen bythe cognizant engineering organization within the PCTFE partmanufacturer unless specifically stated in the procurementdrawing from the procuring agency.12.4.2.1 Method AFor the best dimensional stability, partsshall be machine
38、d to final dimensions with appropriate allow-ances for contraction or expansion during annealing, annealedat 120 6 5 C (248 6 9 F) for 2 h, cooled to roomtemperature, after which dimensional stability shall be deter-mined (12.5).12.4.2.2 Method BFor closest tolerances on a finishedpart, parts shall
39、be machined to approximate dimensions,annealed at 120 6 5 C (248 6 9 F) for 2 h, cooled to roomtemperature, finished to final dimensions, after which dimen-sional stability shall be determined (12.5).NOTE 3Method B is more practical for larger PCTFE parts.12.5 Dimensional Stability12.5.1 Linear dime
40、nsional change shall be determined bycomparing selected dimensions measured before and after ovenheating to simulate accelerated use. Pre- and post-heatingdimensional measurements will be at several reference loca-tions and at multiple locations or both distributed equidistantlyabout the specimen. A
41、fter the initial dimensions have beenmade at 20 to 30 C (68 to 86 F), specimens will be placed inthe preheated oven at 71 6 5 C (160 6 9 F), heated for 48 65 h, after which the specimens will be removed and allowed tocool. After resting for 16 to 24 h (overnight), the finaldimensions will be measure
42、d at 20 to 30 C (68 to 86 F), andthe percent dimensional change, L, calculated as:L 5Lf2 LiLi3100% (2)where:Liand Lf= initial and final dimensions before and afterheating.12.5.2 Measurement of dimensions will always be madewith respect to a known direction such as the MD, TD, orsealing surface.NOTE
43、4Conventional metrological methods (coordinate measuringmachines and dial micrometers) may not have the requisite sensitivity todetect dimensional changes in small parts of the order of 0.3 %. Forexample, a precision micrometer with 0.013-mm (0.0005-in.) sensitivitywill not be able to detect dimensi
44、onal changes smaller than 0.3 % if theoriginal dimension is less than 4.3 mm (0.17 in.). An example would bePCTFE gaskets with thicknesses of the order of 0.50 mm (0.020 in.). Insuch cases, dimensional stability shall be indeterminate and shall notconstitute grounds for nonprocurement.13. Packaging
45、and Package Marking13.1 Finished parts shall be individually packaged in sealedenvelopes, pouches, bags, or other containers in accordancewith the manufacturers commercial practice.13.2 Marking for Shipment13.2.1 Each container shall be legibly and permanentlylabeled with the following information:1
46、3.2.1.1 MaterialPCTFE parts,13.2.1.2 Type I, II or III13.2.1.3 Annealing Method: AorB13.2.1.4 ZSTstock13.2.1.5 Specification numberD719413.2.1.6 Part manufacturers name13.2.1.7 Molders name13.2.1.8 Processing route and date13.2.1.9 Lot number13.2.1.10 Purchase order number13.2.2 For each batch or lo
47、t of PCTFE used in oxygen andair media operated at pressures greater than 11.4 MPa (1650psi) (Type I material) that is subjected to mechanical impacttesting, a unique dash number or part number shall be assignedby the part manufacturer to distinguish it from like PCTFEparts (Type II and III material
48、) for which a unique dash numberor part number shall not be assigned used in (1) oxygen and airmedia at pressures less than 11.4 MPa (1650 psi), (2) oxygenand air media at pressures greater than 11.4 MPa (1650 psi) butfor which mechanical impact testing is not required, (3) inertand reactive media a
49、t the pressures specified in 3.1.4 and 3.1.7,and (4) other media at pressures specified by the cognizantengineering organization.14. Keywords14.1 annealing; dimensional stability; finished parts;PCTFE; polychlorotrifluoroethyleneD7194 124APPENDIX(Nonmandatory Information)X1. SUPPLEMENTARY INFORMATION FROM CORRESPONDING SECTIONS OF PRACTICE (NOTE SECTION NUMBERSREFER TO PARTS OF THE PRACTICE)X1.1 (Section 8.7) Supplementary Property Evaluationson PCTFE semifinished articles and finished partsmachined therefromX1.1.1 The crystallinity, hence mech
