When wire/cable insulation shrinks, the insulation can pull back from a wire termination location. If the wire/cable termination is intended to be environmentally sealed, the insulation shrinkage can create the potential for exposed conductor which may lead to shorting or arcing. In operational environments, insulation shrinkage may also create splits in the wire/cable insulation caused by mechanical stress as the insulation material contracts.
The insulation shrinkage test objective is to evaluate the propensity of a wire or cable’s insulation to shrink with exposure to elevated temperature. The pass/fail criteria for this tests is wire specification specific, but will often only allow for a very small change.