Section 5.3 of ICEA S-81-570 specifies measuring hot creep and hot set of the insulation per ANSI/ICEA T-28-562. For 90°C rated insulation: max 100% elongation (filled) or 175% (unfilled), max 5% set (filled) or 10% (unfilled) at 150°C.
The hot creep test verifies adequate crosslinking of the insulation material, which is critical for maintaining dimensional stability at elevated operating temperatures.