Fracture - RCP
Plastic Pipes Conference Association # 2004 Milan
Patrick Leevers
International Standard ISO 13477 defines the ‘S4’ RCP test itself, and specifies two procedures which use it. The first procedure, already well embedded in referring standards, evaluates a critical pressure at constant temperature (usually 0°C) below which RCP arrests. The second procedure evaluates, at constant pressure, a critical temperature above which RCP arrests. Progress in pipe-grade polyethylenes has led to grades which do not sustain RCP at 0°C; polymer developers use S4 tests to design for a critical temperature as far below 0°C as possible. However, some elements of the S4 critical-temperature protocol may not yet be robust enough for this purpose. This paper reviews two areas of doubt : the choice of a test pressure for critical-temperature tests, and the choice of a pre-test conditioning temperature and set-up procedure.
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