ASTM WK67306

    Revision of F876 - 17 Standard Specification for Crosslinked Polyethylene (PEX) Tubing

    (What is a Work Item?)

    Active Standard: F876 - 20

    Developed by Subcommittee: F17.26 | Committee F17 | Contact Staff Manager



    WK67306


    Keywords

    crosslinked polyethylene; hydrostatic stress; PEX; PPI; pipe; pressure; tubing ;;

    Rationale

    This revision is intended to streamline the method of Environmental Stress Cracking Resistance (ESCR) testing used within Specification F876. The ESCR test has been conducted for many years on PEX tubing made in accordance with Specification F876 at 73F, 180F and 200F. It has been reported that labs performing routine testing of pipe made in accordance with this specification seldom observe samples failing this test, and when submitted pipe sample do fail, they will fail at the highest temperature tested. This observation aligns with polymer engineering theory specifically that at elevated temperatures the polymer matrix relaxes to a state of lower crystallinity which is more susceptible to attack or infiltration by surfactants such as nonylphenoxypoly (ethyeneoxy) ethanol (Igepal CO-630). At the same time elevated temperature makes the surfactant more active which also contributes to making testing at the highest temperature the most severe test. Finally, at the highest temperature, oxidative attack also begins to become significant. Having established that testing at 200F is the most severe test condition, it does not seem reasonable to continue testing the ESCR or PEX tubing also at 73F and 180F. This is even further reinforced by the understanding that there are environmental concerns with the use and disposal of nonylphenoxypoly (ethyeneoxy) ethanol, giving further benefit to the reduction of its use in this test. Further to the routine ESCR testing of PEX tubing made in accordance with Specification F876, the test labs routinely demand NTS tubing for samples. This is because it is difficult to produce the scratch required on the inside of a smaller diameter tube, and because NTS is by far the most common size of tubing made in accordance with the specification. The text of section 7.8 should acknowledge this. Since Igepal CO-630 is a tradename used by a particular manufacturer of nonylphenoxypoly (ethyeneoxy) ethanol, it may not be appropriate to specify the tradename within the specification, which precludes the use of chemically and functionally equivalent materials. Therefore Igepal CO-630 should only be cited as an example of nonylphenoxypoly (ethyeneoxy) ethanol.

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    Work Item Status

    Date Initiated:
    02-28-2019

    Technical Contact:
    Robert Samplonius

    Item:
    003

    Ballot:
    F17.26 (20-04)

    Status:
    Negative Votes Need Resolution

    Item:
    011

    Ballot:
    F17 (19-03)

    Status:
    Withdrawn From Balloting