December 18, 2016
New Accelerated Test Method for Determining Gel Content of PEX Tubing is Published

New ASTM test method F3203 for PEX piping

The new ASTM test method is F3203 and is titled “Test Method for Determination of Gel Content of Crosslinked Polyethylene (PEX) Pipes and Tubing” and claims that the practice is “expected to be equal to or better than the precision of ASTM D2765 methods because this test method requires use of more precise weight measurement and continuous extraction which assures extraction with pure solvent. This significantly improves repeatability. As mentioned in ASTM D2765, Note 2, the accuracy is 1 to 2% better using a Soxhlet Extractor. In general this method will have a bias in the results of 0 to 1% lower gel content measured than would be measured with ASTM D2765 method A”.  The test method describes the apparatus, the reagents used as antioxidants and refluxing solvents, safety precautions, the test specimens used, the procedure, the calculation used to determine gel content, and the reporting.  Although an interlaboratory precision and bias testing study has not yet been completed, the test method does include the results of two intralaboratory studies.

This test method shows 5 hours using boiling xylene extraction.  The current test method cited by ASTM F876 – ASTM D2765 – uses either boiling decahydronaphthalene (Decalin) for 6 hours or 12 hours in boiling xylenes.  By cutting the extraction time in half, this test method may be of greatest value to PEX tubing manufacturers who may repeat this test many times in a month to ensure the quality of their tubing consistently meets the requirements of the standard.
Link to ASTM Announcement

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