The present invention relates to a molded article of a crosslinked ethylenic
polymer foam. The molded article of a crosslinked ethylenic
polymer foam has a crosslinking density of 0.30 mol / kg or higher as determined using a
relaxation modulus based on a
stress relaxation measurement obtained by measuring the
stress relaxation of the molded article of the crosslinked foam when the molded article of the crosslinked foam is subjected to
compressive deformation under conditions of a measurement temperature of 60 C, compressive strain of 50%, and a measurement time of 1,800 seconds. The present invention also relates to a method for measuring the crosslinking density of a molded article of a crosslinked
thermoplastic polymer foam, the method comprising: a step for heating the molded article of the crosslinked
thermoplastic polymer foam to a predetermined temperature; a step for applying pressure to the molded article of the crosslinked
thermoplastic polymer foam, which is maintained at the predetermined temperature, in order to induce
compressive deformation of the molded article of the crosslinked foam, and for measuring the
stress relaxation of the molded article of the crosslinked foam while the compressive strain of the molded article of the crosslinked foam is maintained at a constant level; a step for determining a
relaxation modulus (Gc) from the stress relaxation; and a step for calculating the crosslinking density of the crosslinked
thermoplastic polymer foam from Gc using the following formula in which Gc is the
elastic modulus when the stress of the molded article of the crosslinked foam is at a constant level: n = Gc / RT (n: crosslinking density, R:
gas constant, T: measurement temperature).