ASTM D7194 - 12

    Standard Specification for Aerospace Parts Machined from Polychlorotrifluoroethylene (PCTFE)

    Active Standard ASTM D7194 | Developed by Subcommittee: D20.15

    Book of Standards Volume: 08.03


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    Abstract

    This specification establishes the requirements for parts intended for aerospace use and machined from polychlorotrifluoroethylene (PCTFE) homopolymers. This specification, however, does not cover parts machined from PCTFE copolymer, PCTFE film or tape, or modified PCTFE. Material covered by this specification is on four types, differentiated based on intended uses and exposures: Types I (high service pressure) and II (low service pressure) for use in air and oxygen media, Type II for use in inert and reactive media, and Type IV for use in other media. The parts shall be manufactured from virgin, unplasticized, pure PCTFE homopolymer, and the use of recycled polymer or regrind shall be prohibited. The base material shall be free of defects and contaminants. The finished parts shall be white or gray in color with a natural translucent appearance, and shall be free of voids, scratches, fissures, inclusions, or entrapped air bubbles. Tests for specific gravity, melting point, tensile strength and elongation, deformation under load, zero strength time, mechanical impact (in ambient liquid oxygen and pressurized liquid and gaseous oxygen environments), and dimensional stability shall be performed and shall conform to the requirements specified.

    This abstract is a brief summary of the referenced standard. It is informational only and not an official part of the standard; the full text of the standard itself must be referred to for its use and application. ASTM does not give any warranty express or implied or make any representation that the contents of this abstract are accurate, complete or up to date.

    Significance and Use

    1. Scope

    1.1 This specification is intended to be a means of calling out finished machined parts ready for aerospace use. Such parts may also find use in selected commercial applications where there are clear benefits derived from the use of parts with known or controlled crystallinity, high molecular weight, good molecular weight retention during processing, dimensional stability in the finished part, and tightly controlled engineering tolerances.

    1.2 This specification establishes requirements for parts machined from virgin, unplasticized, 100 % polychlorotrifluoroethylene (PCTFE) homopolymers.

    1.3 This specification does not cover parts machined from PCTFE copolymers, PCTFE film or tape less than 0.25-mm (0.010-in.) thick, or modified PCTFE (containing pigments or plasticizers).

    1.4 This specification does not allow parts containing recycled material.

    1.5 The specification does not cover PCTFE parts intended for general use applications, in which control of dimensional stability, molecular weight, and crystallinity are not as important. For machined PCTFE parts intended for general use, use Specification D7211.

    1.6 This specification classifies parts into three classes based upon intended uses and exposures: oxygen-containing media, reactive media, and inert media.

    1.7 Application—PCTFE components covered by this specification are virgin, 100 % PCTFE resin, free of plasticizers and other additives. The components are combustion resistant in oxygen, dimensionally stable, and meet other specific physical characteristics appropriate for their end use. They are used in valves, regulators, and other devices in oxygen, air, helium, nitrogen, hydrogen, ammonia, and other aerospace media systems. The components typically are used as valve seats, o-rings, seals, and gaskets. They are removed and replaced during normal maintenance procedures. The components provide reliable sealing surfaces resulting in proper closure of valves and related devices and no leakage from the system into the environment. They will experience static mechanical loading, cyclic mechanical loading, temperatures ranging from cryogenic to 71 ºC (160 ºF), and pressures up to 68.9 MPa (10,000, psig) for oxygen and air media, and 103.4 MPa (15,000 psig) for inert media.

    1.8 The values stated in SI units are to be regarded as standard. The values in parentheses are for information only.

    1.9 The following precautionary caveat pertains only to the test methods portion, Section 12, of this specification: This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and to determine the applicability of regulatory limitations prior to use.

    Note 1There is no known ISO equivalent to this standard.


    2. Referenced Documents (purchase separately) The documents listed below are referenced within the subject standard but are not provided as part of the standard.

    ASTM Standards

    D618 Practice for Conditioning Plastics for Testing

    D638 Test Method for Tensile Properties of Plastics

    D792 Test Methods for Density and Specific Gravity (Relative Density) of Plastics by Displacement

    D883 Terminology Relating to Plastics

    D1430 Classification System for Polychlorotrifluoroethylene (PCTFE) Plastics

    D1600 Terminology for Abbreviated Terms Relating to Plastics

    D1708 Test Method for Tensile Properties of Plastics by Use of Microtensile Specimens

    D2512 Test Method for Compatibility of Materials with Liquid Oxygen (Impact Sensitivity Threshold and Pass-Fail Techniques)

    D4591 Test Method for Determining Temperatures and Heats of Transitions of Fluoropolymers by Differential Scanning Calorimetry

    D7211 Specification for Parts Machined from Polychlorotrifluoroethylene (PCTFE) and Intended for General Use

    G86 Test Method for Determining Ignition Sensitivity of Materials to Mechanical Impact in Ambient Liquid Oxygen and Pressurized Liquid and Gaseous Oxygen Environments

    Federal Standards

    NASA-STD-6001B Flammability, Offgassing, and Compatibility Requirements and Test Procedures--Mechanical Impact for Materials in Ambient Pressure LOX (Test 13A) and Mechanical Impact for Materials in Variable Pressure GOX and LOX (Test 13B)


    ICS Code

    ICS Number Code 49.025.40 (Rubber and plastics); 49.140 (Space systems and operations)

    UNSPSC Code

    UNSPSC Code 25201500(Aircraft fuselage and components)


    DOI: 10.1520/D7194-12

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