Fracture - RCP # 2004 Milan
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.