Heat reversion testing evaluates the dimensional stability of PVC pipes under high temperature exposure. Per European and ISO standards, a pipe sample is heated to 150°C and the length shrinkage must not exceed 5%. This assesses the degree of heat reversion, which is the pipe’s length shrinkage caused by thermal exposure. Excessive reversion commonly results from overstretching the free extrudate during co-extrusion or extrusion processing.
Excessive heat reversion poses risks to joint integrity, particularly in applications involving hot water discharge (e.g., dishwasher drainage or industrial wastewater). Prolonged shrinkage can cause spigot retraction from rubber ring sealed sockets, leading to leakage or joint failure.